Temporal changes in chromosome abnormalities in human spontaneous abortions: Results of 40 years of analysis

Lessons learned from 64,071 embryos subjected to PGT for aneuploidies: results, recurrence pattern and indications analysis

RESEARCH QUESTION

What is the influence of biological, technical and clinical factors on embryo outcomes in preimplantation genetic testing for aneuploidies (PGT-A) and what is the recurrence pattern?

DESIGN

This retrospective study included 64,071 embryos undergoing PGT-A in the same laboratory between 2011 and 2019. Biopsies were performed at the day 3 embryo stage (48.32%) or blastocyst stage (51.70%). Advanced maternal age (AMA) was the main indication (65.62%).

RESULTS

The aneuploidy rate was 67.75%, higher in women aged over 35 years than in women aged 35 years or less (71.76% versus 47.44%), and higher in day 3 embryo versus blastocyst biopsies (77.51% versus 58.62%). The trisomy:monosomy ratio was 1.01 for blastocysts versus 0.84 for day 3 embryos. Trisomy 21 was present in 4.9% of embryos. In aneuploid embryos, the probability of having one or more involved chromosomes followed a decreasing exponential pattern. The probability of an embryo being euploid was constant at around 30% (40% in blastocysts, 20% in day 3 embryos). The cumulative probability of having one or more euploid embryos after 10 biopsied embryos was 94.79% in blastocysts and 80.61% in day 3 embryos. AMA was associated with a much higher aneuploidy rate than all other indications, which among them had similar aneuploidy rate and chromosomal involvement.

CONCLUSIONS

There is a considerably lower aneuploidy rate in blastocysts than day 3 embryos, which is most notable for monosomies. While AMA shows an increased aneuploidy rate and a specific chromosomal pattern of involvement, the remaining indications showed a similar aneuploidy rate and chromosomal pattern. Even after producing many consecutive aneuploid embryos, the possibility of obtaining a euploid embryo is not negligible.

Vanishing twins, spared cohorts, and the birthweight of periviable infants born to Black and white women in the United States

Pregnancies ending before 26 weeks contribute 1% of births but 40% of infant deaths in the United States. The rate of these "periviable" births to non-Hispanic (NH) Black women exceeds four times that for NH whites. Small male periviable infants remain most likely to die. NH white periviable males weigh more than their NH Black counterparts. We argue that male infants born from twin gestations, in which one fetus died in utero (i.e., the vanishing twin syndrome), contribute to the disparity. We cannot directly test our argument because "vanishing" typically occurs before clinical recognition of pregnancy. We, however, describe and find associations that would emerge in vital statistics were our argument correct. Among male periviable singleton births from 288 monthly conception cohorts (January 1995 through December 2018), we found an average NH white advantage of 30 grams (759 grams versus 729 grams). Consistent with our argument, however, cohorts signaling relatively few survivors of the vanishing twin syndrome showed no disparity.

Male twinning after the 2008 Obama election: A test of symbolic empowerment

On November 4, 2008, Barack Obama was elected the first Black President of the United States. His campaign and electoral win served as a symbol of hope for a more just future, fostering an "Obama effect" that appears associated with improved well-being among non-Hispanic (NH) Black communities. Situating the Obama election within the symbolic empowerment framework, we consider the potentially protective role of the Obama election on NH Black fetal death, an important but understudied measure of perinatal health that has stark racial disparities. Using restricted-use natality files from the National Center for Health Statistics, we proxy fetal death using the male twin rate (number of twins per 1000 male live births). Male twins have a relatively high risk of in utero selection that is sensitive to maternal and environmental stressors, making the twin rate an important marker of fetal death. We then estimate interrupted time-series models to assess the relation between the Obama election and male twin rates among NH Black births across monthly conception cohorts (February 2003-October 2008). Greater-than-expected male twin rates signal less susceptibility to fetal loss. Results indicate a 4.5% higher male twin rate among all NH Black cohorts exposed in utero to the Obama election, after accounting for historical and NH white trends (p < 0.005). The greater-than-expected rates concentrated among births conceived in the months preceding Obama's nomination at the Democratic National Convention and Obama's presidential win. These results suggest a salutary perinatal response to election events that likely reduced NH Black fetal loss. They also indicate the possibility that sociopolitical shifts can mitigate persisting NH Black-NH white disparities in perinatal health.

Primary cilia abnormalities participate in the occurrence of spontaneous abortion through TGF-β/SMAD2/3 signaling pathway

Spontaneous abortion is the most common complication in early pregnancy, the exact etiology of most cases cannot be determined. Emerging studies suggest that mutations in ciliary genes may be associated with progression of pregnancy loss. However, the involvement of primary cilia on spontaneous abortion and the underlying molecular mechanisms remains poorly understood. We observed the number and length of primary cilia were significantly decreased in decidua of spontaneous abortion in human and lipopolysaccharide (LPS)-induced abortion mice model, accompanied with increased expression of proinflammatory cytokines interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α. The length of primary cilia in human endometrial stromal cell (hESC) was significantly shortened after TNF-α treatment. Knocking down intraflagellar transport 88 (IFT88), involved in cilia formation and maintenance, promoted the expression of TNF-α. There was a reverse regulatory relationship between cilia shortening and TNF-α expression. Further research found that shortened cilia impair decidualization in hESC through transforming growth factor (TGF)-β/SMAD2/3 signaling. Primary cilia were impaired in decidua tissue of spontaneous abortion, which might be mainly caused by inflammatory injury. Primary cilia abnormalities resulted in dysregulation of TGF-β/SMAD2/3 signaling transduction and decidualization impairment, which led to spontaneous abortion.

Cell-Free DNA Analysis of Fetal Aneuploidies in Early Pregnancy Loss

Background: Products of conception samples are often collected and analyzed to try to determine the cause of an early pregnancy loss. However, sample collection may not always be possible, and maternal cell contamination and culture failure can affect the analysis. Cell-free DNA-based analysis of a blood sample could be used as an alternative method in early pregnancy loss cases to detect if aneuploidies were present in the fetus. Methods: In this prospective study, blood samples from early pregnancy loss patients were analyzed for the presence of fetal aneuploidies using a modified version of a noninvasive prenatal testing assay for cell-free DNA analysis. Results from cell-free DNA analysis were compared against the gold standard, microarray analysis of products of conception samples. This study was registered with ClinicalTrials.gov, identifier: NCT04935138. Results: Of the 76 patient samples included in the final study cohort, 11 were excluded from performance calculations. The 65 patient samples included in the final analysis included 49 with an abnormal microarray result and 16 with a normal microarray result. Based on results from these 65 samples, the study found that genome-wide cell-free DNA analysis had a sensitivity of 73.5% with a specificity of 100% for the detection of fetal aneuploidies in early pregnancy loss cases. Conclusions: This prospective study provides further support for the utility of cell-free DNA analysis in detecting fetal aneuploidies in early pregnancy loss cases. This approach could allow for a noninvasive method of investigating the etiology of miscarriages to be made available clinically.

Direct embryonic biopsy with transcervical embryoscopy is an effective method for karyotyping and morphology assessment in miscarriages

PURPOSE

The main purpose of this study is to compare the validity of transcervical embryoscopy method with standard uterine evacuation method in detecting more accurate karyotypes in miscarriages below tenth week of pregnancy. Additionally, the frequency and distribution of fetal morphological abnormality were evaluated.

METHODS

A prospective study was carried out at the Gazi University Faculty of Medicine, Department of Obstetrics and Gynecology. Patients with missed abortions between sixth and tenth gestational weeks were included in the study group, and fetal morphological examination and direct embryonic biopsy were performed by transcervical embryoscopy. The control group consisted of patients who experienced miscarriage and genetic material obtained from routine uterine evacuation between February and October 2023.

RESULT

A total of 60 patients in the study group and 189 patients in the control group were evaluated. The median ages, previous miscarriage numbers, median gravida numbers, and median gestational weeks were comparable between groups. Chromosomal abnormality was detected in 24 (42.8%) and 52 embryos (29.9%) in the study and control groups, respectively (p = 0.004). Culture failure rates were 6.6% (n = 4) and 7.9% (n = 15) in the study and control groups, respectively. In the study group, 12 embryos had a morphological abnormality in which 6 of them had normal karyotype.

CONCLUSION

Direct embryonic biopsy with transcervical embryoscopy is an effective method to exclude maternal decidual cell contamination and placental mosaicism in miscarriages for karyotype analysis. In addition, detecting anomalies in morphology might contribute our understanding in the process of miscarriages which arises independent from structural/numerical chromosomal abnormalities.

The chromosomal characteristics of spontaneous abortion and its potential associated copy number variants and genes

PURPOSE

This study aimed to investigate the correlation between chromosomal abnormalities in spontaneous abortion with clinical features and seek copy number variations (CNVs) and genes that might be connected to spontaneous abortion.

METHODS

Over 7 years, we used CNV-seq and STR analysis to study POCs, comparing chromosomal abnormalities with clinical features and identifying critical CNVs and genes associated with spontaneous abortion.

RESULTS

Total chromosomal variants in the POCs were identified in 66.8% (2169/3247) of all cases, which included 45.2% (1467/3247) numerical abnormalities and 21.6% (702/3247) copy number variants (CNVs). Chromosome number abnormalities, especially aneuploidy abnormalities, were more pronounced in the group of mothers aged ≥ 35 years, the early miscarriage group, and the chorionic villi group. We further analyzed 212 pathogenic and likely pathogenic CNVs in 146 POCs as well as identified 8 statistically significant SORs through comparison with both a healthy population and a group of non-spontaneously aborted fetuses. Our analysis suggests that these CNVs may play a crucial role in spontaneous abortion. Furthermore, by utilizing the RVIS score and MGI database, we identified 86 genes associated with spontaneous abortion, with particular emphasis on PARP6, ISLR, ULK3, FGFRL1, TBC1D14, SCRIB, and PLEC.

CONCLUSION

We found variability in chromosomal abnormalities across clinical features, identifying eight crucial copy number variations (CNVs) and multiple key genes that may be linked to spontaneous abortion. This research enhances the comprehension of genetic factors contributing to spontaneous abortion.

Trophectoderm cells of human mosaic embryos display increased apoptotic levels and impaired differentiation capacity: a molecular clue regarding their reproductive fate?

STUDY QUESTION

Are there cell lineage-related differences in the apoptotic rates and differentiation capacity of human blastocysts diagnosed as euploid, mosaic, and aneuploid after preimplantation genetic testing for aneuploidy (PGT-A) based on concurrent copy number and genotyping analysis?

SUMMARY ANSWER

Trophectoderm (TE) cells of mosaic and aneuploid blastocysts exhibit significantly higher levels of apoptosis and significantly reduced differentiation capacity compared to those of euploid blastocysts.

WHAT IS KNOWN ALREADY

Embryos diagnosed as mosaic after PGT-A can develop into healthy infants, yet understanding the reasons behind their reproductive potential requires further research. One hypothesis suggests that mosaicism can be normalized through selective apoptosis and reduced proliferation of aneuploid cells, but direct evidence of these mechanisms in human embryos is lacking. Additionally, data interpretation from studies involving mosaic embryos has been hampered by retrospective analysis methods and the high incidence of false-positive mosaic diagnoses stemming from the use of poorly specific PGT-A platforms.

STUDY DESIGN, SIZE, DURATION

Prospective cohort study performing colocalization of cell-lineage and apoptotic markers by immunofluorescence (IF). We included a total of 64 human blastocysts donated to research on Day 5 or 6 post-fertilization (dpf) by 43 couples who underwent in vitro fertilization treatment with PGT-A at IVI-RMA Valencia between September 2019 and October 2022. A total of 27 mosaic blastocysts were analyzed.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The study consisted of two phases: Phase I (caspase-3, n = 53 blastocysts): n = 13 euploid, n = 22 mosaic, n = 18 aneuploid. Phase II (terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL), n = 11 blastocysts): n = 2 euploid, n = 5 mosaic, n = 4 aneuploid. Following donation for research, vitrified blastocysts were warmed, cultured until re-expansion, fixed, processed for IF, and imaged using confocal microscopy. For each blastocyst, the following cell counts were conducted: total cells (DAPI+), TE cells (GATA3+), inner cell mass (ICM) cells (GATA3-/NANOG+), and apoptotic cells (caspase-3+ or TUNEL+). The incidence of apoptosis was calculated for each blastocyst by dividing the number of caspase-3+ cells (Phase I) or TUNEL+ cells (Phase II) by the number of TE or ICM cells. Statistical analysis was performed according to data type and distribution (P < 0.05 was considered statistically significant).

MAIN RESULTS AND THE ROLE OF CHANCE

Phase I: Mosaic blastocysts displayed a similar number of total cells (49.6 ± 15 cells at 5 dpf; 58.8 ± 16.9 cells at 6 dpf), TE cells (38.8 ± 13.7 cells at 5 dpf; 49.2 ± 16.2 cells at 6 dpf), and ICM cells (10.9 ± 4.2 cells at 5 dpf; 9.7 ± 7.1 cells at 6 dpf) compared to euploid and aneuploid blastocysts (P > 0.05). The proportion of TE cells retaining NANOG expression increased gradually from euploid blastocysts (9.7% = 63/651 cells at 5 dpf; 0% = 0/157 cells at 6 dpf) to mosaic blastocysts (13.1% = 104/794 cells at 5 dpf; 3.4% = 12/353 cells at 6 dpf) and aneuploid blastocysts (27.9% = 149/534 cells at 5 dpf; 4.6% = 19/417 cells at 6 dpf) (P < 0.05). At the TE level, caspase-3+ cells were frequently observed (39% = 901/2310 cells). The proportion of caspase-3+ TE cells was significantly higher in mosaic blastocysts (44.1% ± 19.6 at 5 dpf; 43% ± 16.8 at 6 dpf) and aneuploid blastocysts (45.9% ± 16.1 at 5 dpf; 49% ± 15.1 at 6 dpf) compared to euploid blastocysts (26.6% ± 16.6 at 5 dpf; 17.5% ± 14.8 at 6 dpf) (P < 0.05). In contrast, at the ICM level, caspase-3+ cells were rarely observed (1.9% = 11/596 cells), and only detected in mosaic blastocysts (2.6% = 6/232 cells) and aneuploid blastocysts (2.5% = 5/197 cells) (P > 0.05). Phase II: Consistently, TUNEL+ cells were only observed in TE cells (32.4% = 124/383 cells). An increasing trend was identified toward a higher proportion of TUNEL+ cells in the TE of mosaic blastocysts (37.2% ± 21.9) and aneuploid blastocysts (39% ± 41.7), compared to euploid blastocysts (23% ± 32.5), although these differences did not reach statistical significance (P > 0.05).

LIMITATIONS, REASONS FOR CAUTION

The observed effects on apoptosis and differentiation may not be exclusive to aneuploid cells. Additionally, variations in aneuploidies and unexplored factors related to blastocyst development and karyotype concordance may introduce potential biases and uncertainties in the results.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings demonstrate a cell lineage-specific effect of aneuploidy on the apoptotic levels and differentiation capacity of human blastocysts. This contributes to unravelling the biological characteristics of mosaic blastocysts and supports the concept of clonal depletion of aneuploid cells in explaining their reproductive potential.

STUDY FUNDING/COMPETING INTEREST(S)

This work was funded by grants from Centro para el Desarrollo Tecnológico Industrial (CDTI) (20190022) and Generalitat Valenciana (APOTIP/2019/009). None of the authors has any conflict of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Variant in the synaptonemal complex protein SYCE2 associates with pregnancy loss through effect on recombination

Two-thirds of all human conceptions are lost, in most cases before clinical detection. The lack of detailed understanding of the causes of pregnancy losses constrains focused counseling for future pregnancies. We have previously shown that a missense variant in synaptonemal complex central element protein 2 (SYCE2), in a key residue for the assembly of the synaptonemal complex backbone, associates with recombination traits. Here we show that it also increases risk of pregnancy loss in a genome-wide association analysis on 114,761 women with reported pregnancy loss. We further show that the variant associates with more random placement of crossovers and lower recombination rate in longer chromosomes but higher in the shorter ones. These results support the hypothesis that some pregnancy losses are due to failures in recombination. They further demonstrate that variants with a substantial effect on the quality of recombination can be maintained in the population.

Non-invasive cell-free DNA-based approach for the diagnosis of clinical miscarriage: A retrospective study

OBJECTIVE

To evaluate cell-free DNA (cfDNA) testing as a non-invasive approach to detecting aneuploidies in clinical miscarriages.

DESIGN

A retrospective cohort study of women with pregnancy loss.

SETTING

Hospitals and genetic analysis laboratories.

POPULATION OR SAMPLE

Pregnancy losses in the period 2021-2022.

METHODS

Results derived from non-invasive cfDNA testing (Veriseq NIPT Solution V2) of maternal blood and invasive analysis of products of conception (POC) (Ion ReproSeq) compared in 120 women who suffered a miscarriage.

MAIN OUTCOME MEASURES

Concordance rate results, cfDNA testing performance, non-informative rate (NIR) and fetal fraction (FF).

RESULTS

We found no significant differences in the NIR between invasive (iPOC) and non-invasive (niPOC) analysis of POC (10.0% [12/120] versus 16.7% [20/120]). Of 120 samples, 90 provided an informative result in iPOC and niPOC groups (75%). cfDNA analysis correctly identified 74/87 (85.1%) samples (excluding triploidies). Sensitivity and specificity were 79.4% and 100%, respectively; all discordant cases were female. A binomial logistic model suggested fetal sex as the only variable influencing the concordance rate (P = 0.035). A Y-chromosome-based FF estimate allowed the optimal reclassification of cfDNA of non-informative male fetuses and a more accurate evaluation of cfDNA testing performance. The difference between the two FF estimates (native algorithm and Y-chromosome-based) suggests that female non-concordant cases may represent non-informative cases.

CONCLUSIONS

Cell-free DNA-based testing provides a non-invasive approach to determining the genetic cause of clinical miscarriage.

Improving access, understanding, and dignity during miscarriage recovery in British Columbia, Canada: A patient-oriented research study

BACKGROUND

Approximately 15%-25% of clinical pregnancies end in miscarriage, with more than 15,000 miscarriages occurring annually in British Columbia, Canada. Despite the significant rates of loss, research and health care services for pregnancy loss remain scarce in British Columbia.

OBJECTIVES

This study aimed to (1) aid miscarriage recovery through the identification and sharing of equitable pregnancy loss care practices and supports and (2) present policy recommendations to improve prenatal care guidelines and employment standards for pregnancy loss.

DESIGN

This research took a patient-oriented methodological approach alongside people with lived/living experience(s) of miscarriage recovery in British Columbia to evaluate access to health care during pregnancy loss, societal understanding of miscarriage, and treatment options that foreground dignity.

METHODS

The mixed-methods design of this research included policy research on prenatal care guidelines, policy research on provincial and territorial employment legislation for bereavement leave, semi-structured interviews (n = 27), and a discovery action dialogue (n = 4).

RESULTS

The findings of this research demonstrate the need for improved prenatal care guidelines for early pregnancy loss, follow-up care after a miscarriage, mental health screening and supports, and bereavement leave legislation.

CONCLUSION

This article includes recommendations to improve equitable access to pregnancy loss care, bereavement leave legislation, and future research in this area.

Prevalence of chromosomal alterations in first-trimester spontaneous pregnancy loss

Pregnancy loss is often caused by chromosomal abnormalities of the conceptus. The prevalence of these abnormalities and the allocation of (ab)normal cells in embryonic and placental lineages during intrauterine development remain elusive. In this study, we analyzed 1,745 spontaneous pregnancy losses and found that roughly half (50.4%) of the products of conception (POCs) were karyotypically abnormal, with maternal and paternal age independently contributing to the increased genomic aberration rate. We applied genome haplarithmisis to a subset of 94 pregnancy losses with normal parental and POC karyotypes. Genotyping of parental DNA as well as POC extra-embryonic mesoderm and chorionic villi DNA, representing embryonic and trophoblastic tissues, enabled characterization of the genomic landscape of both lineages. Of these pregnancy losses, 35.1% had chromosomal aberrations not previously detected by karyotyping, increasing the rate of aberrations of pregnancy losses to 67.8% by extrapolation. In contrast to viable pregnancies where mosaic chromosomal abnormalities are often restricted to chorionic villi, such as confined placental mosaicism, we found a higher degree of mosaic chromosomal imbalances in extra-embryonic mesoderm rather than chorionic villi. Our results stress the importance of scrutinizing the full allelic architecture of genomic abnormalities in pregnancy loss to improve clinical management and basic research of this devastating condition.

Chromosomal abnormalities in recurrent pregnancy loss and its association with clinical characteristics

OBJECTIVE

To evaluate the distribution of chromosomal abnormalities in a recurrent pregnancy loss (RPL) cohort and explore the associations between chromosomal abnormalities and clinical characteristics.

METHOD

Over a 5-year period, fresh products of conception (POC) from women with RPL were analyzed by single-nucleotide polymorphism (SNP) array at our hospital. After obtaining the information on clinical characteristics, we investigated the associations between the causative chromosomal abnormalities and clinical characteristics by the chi-squared test or Fisher's exact test and logistic regression.

RESULTS

A total of 2383 cases were enrolled. Overall, 56.9% (1355/2383) were identified with causative chromosomal abnormalities, of which 92.1% (1248/1355) were numerical abnormalities, 7.5% (102/1355) were structural variants, and 0.4% (5/1355) were loss of heterozygosity (LOH). The risk of numerical abnormalities was increased in women with maternal age ≥ 35 years (OR, 1.71; 95% CI, 1.41-2.07), gestational age at pregnancy loss ≤ 12 weeks (OR, 2.78; 95% CI, 1.79-4.33), less number of previous pregnancy losses (twice: OR, 2.32; 95% CI, 1.84-2.94; 3 times: OR, 1.59; 95% CI, 1.23-2.05, respectively), and pregnancy with a female fetus (OR, 1.37; 95% CI, 1.15-1.62). The OR of pregnancy loss with recurrent abnormal CMA was 4.00 (95% CI: 1.87-8.58, P < 0.001) and the adjusted OR was 5.05 (95% CI: 2.00-12.72, P = 0.001). However, the mode of conception was not associated with the incidence of numerical abnormality. No association was noted between structural variants and clinical characteristics.

CONCLUSION

Chromosomal abnormality was the leading cause of RPL. Numerical chromosome abnormality was more likely to occur in cases with advanced maternal age, an earlier gestational age, fewer previous pregnancy losses, and pregnancy with a female fetus.

Human embryo implantation

Embryo implantation in humans is interstitial, meaning the entire conceptus embeds in the endometrium before the placental trophoblast invades beyond the uterine mucosa into the underlying inner myometrium. Once implanted, embryo survival pivots on the transformation of the endometrium into an anti-inflammatory placental bed, termed decidua, under homeostatic control of uterine natural killer cells. Here, we examine the evolutionary context of embryo implantation and elaborate on uterine remodelling before and after conception in humans. We also discuss the interactions between the embryo and the decidualising endometrium that regulate interstitial implantation and determine embryo fitness. Together, this Review highlights the precarious but adaptable nature of the implantation process.

Cell-free fetal DNA for genetic evaluation in Copenhagen Pregnancy Loss Study (COPL): a prospective cohort study

BACKGROUND

One in four pregnancies end in a pregnancy loss. Although the effect on couples is well documented, evidence-based treatments and prediction models are absent. Fetal aneuploidy is associated with a higher chance of a next successful pregnancy compared with euploid pregnancy loss in which underlying maternal conditions might be causal. Ploidy diagnostics are therefore advantageous but challenging as they require collection of the pregnancy tissue. Cell-free fetal DNA (cffDNA) from maternal blood has the potential for evaluation of fetal ploidy status, but no large-scale validation of the method has been done.

METHODS

In this prospective cohort study, women with a pregnancy loss were recruited as a part of the Copenhagen Pregnancy Loss (COPL) study from three gynaecological clinics at public hospitals in Denmark. Women were eligible for inclusion if older than 18 years with a pregnancy loss before gestational age 22 weeks (ie, 154 days) and with an intrauterine pregnancy confirmed by ultrasound (including anembryonic sac), and women with pregnancies of unknown location or molar pregnancies were excluded. Maternal blood was collected while pregnancy tissue was still in situ or within 24 h after pregnancy tissue had passed and was analysed by genome-wide sequencing of cffDNA. Direct sequencing of the pregnancy tissue was done as reference.

FINDINGS

We included 1000 consecutive women, at the time of a pregnancy loss diagnosis, between Nov 12, 2020, and May 1, 2022. Results from the first 333 women with a pregnancy loss (recruited between Nov 12, 2020, and Aug 14, 2021) were used to evaluate the validity of cffDNA-based testing. Results from the other 667 women were included to evaluate cffDNA performance and result distribution in a larger cohort of 1000 women in total. Gestational age of fetus ranged from 35-149 days (mean of 70·5 days [SD 16·5], or 10 weeks plus 1 day). The cffDNA-based test had a sensitivity for aneuploidy detection of 85% (95% CI 79-90) and a specificity of 93% (95% CI 88-96) compared with direct sequencing of the pregnancy tissue. Among 1000 cffDNA-based test results, 446 (45%) were euploid, 405 (41%) aneuploid, 37 (4%) had multiple aneuploidies, and 112 (11%) were inconclusive. 105 (32%) of 333 women either did not manage to collect the pregnancy tissue or collected a sample classified as unknown tissue giving a high risk of being maternal.

INTERPRETATION

This validation of cffDNA-based testing in pregnancy loss shows the potential and feasibility of the method to distinguish euploid and aneuploid pregnancy loss for improved clinical management and benefit of future reproductive medicine and women's health research.

FUNDING

Ole Kirks Foundation, BioInnovation Institute Foundation, and the Novo Nordisk Foundation.

Identifying parental and cell-division origins of aneuploidy in the human blastocyst

Preimplantation genetic testing commonly employs simplistic copy-number analyses to screen for aneuploidy in blastocyst trophectoderm biopsies. Interpreting intermediate copy number alone as evidence of mosaicism has led to suboptimal estimation of its prevalence. Because mosaicism originates from mitotic nondisjunction, utilizing SNP microarray technology to identify the cell-division origins of aneuploidy might provide a more accurate estimation of its prevalence. The present study develops and validates a method of determining the cell-division origin of aneuploidy in the human blastocyst by using both genotyping and copy-number data in parallel. The concordance of predicted origins with expected results was demonstrated in a series of truth models (99%-100%). This included determination of X chromosome origins from a subset of normal male embryos, determination of the origins of translocation chromosome-related imbalances via embryos from couples with structural rearrangements, and prediction of either mitotic or meiotic origins via multiple rebiopsies of embryos with aneuploidy. In a cohort of blastocysts with parental DNA (n = 2,277), 71% were euploid, 27% were meiotic aneuploid, and 2% were mitotic aneuploid, indicating a low frequency of bona fide mosaicism in the human blastocyst (mean maternal age: 34.4). Chromosome-specific trisomies in the blastocyst were also consistent with observations previously established in products of conception. The ability to accurately identify mitotic-origin aneuploidy in the blastocyst could benefit and better inform individuals whose IVF cycle results in all aneuploid embryos. Clinical trials with this methodology might also help provide a definitive answer regarding the reproductive potential of bona fide mosaic embryos.

Single-cell profiling of the microenvironment in decidual tissue from women with missed abortions

OBJECTIVE

To define the decidual microenvironment in euploid and aneuploid missed abortions and elective termination of pregnancies.

DESIGN

Prospective, multicenter, observational study.

SETTING

Tertiary hospital and descriptive analysis of transcriptomic data.

PATIENT(S)

A total of 34 patients experienced abortions, including 6 women who underwent elective terminations of pregnancy of unplanned pregnancies and 28 cases with missed abortions. All patients underwent their operations from Sep, 2021 to Sep, 2022.

INTERVENTION(S)

All women underwent villous copy number variation sequencing. Meanwhile, single-cell RNA sequencing were performed in the decidual tissues of 16 women, and reverse transcription quantitative polymerase chain reaction were performed in the decidual tissues of 18 women.

MAIN OUTCOME MEASURE(S)

Single-cell RNA sequencing was used to explore the changes in the microenvironment of decidual tissues in abortions.

RESULT(S)

Single-cell RNA sequencing indicated that the microenvironment of the decidual tissue of the missed-abortion group was altered, and that the stromal cells (SCs), natural killer cells, macrophages, and epithelial cells all reflected functional imbalances compared with the elective terminations of pregnancy group. We also noted a correlation between the proportion of senescent SCs and chromosomal abnormalities in missed-abortion embryos. The proportion of senescent decidual SCs in the decidual tissue of missed-abortion patients with common chromosomal abnormalities of the fetus was higher, and this was not conducive to fetal growth and was closely related to missed abortion. In addition, we ascertained that the strength of the HLA-KIR interaction between NK1 and NK2 subsets and non-senescent stromal cell subsets in the missed abortion decidual tissues was weakened, potentially playing a role in the occurrence of missed abortion.

CONCLUSION(S)

The decidualization of SCs in the missed-abortion decidual tissues was impaired, the clearance of senescent SCs by NK cells was weakened, the killing toxicity of non-senescent SCs was enhanced, macrophages were insufficiently resident at the maternal-fetal interface, and epithelial cell differentiation was unbalanced-all creating a maternal microenvironment that was not conducive to fetal growth. We posit that interfering with the expression of dysregulated genes in the missed-abortion decidual tissues and reversing the maternal microenvironment might constitute an effective means toward improving the clinical outcome of missed abortions. Intriguingly, we observed a correlation between stromal cell senescence and embryonic chromosomal abnormalities. Thus, we hypothesize that the DIO2 marker of senescent SCs can be used as a risk indicator for the occurrence of missed miscarriages with chromosomal abnormalities of the embryos, and that it can be applied to guide the clinical diagnosis and treatment of recurrent abortion.

CLINICAL TRIAL REGISTRATION NUMBER

NCT04425317.

Comparative cytogenetics of anembryonic pregnancies and missed abortions in human

Miscarriage is an important problem in human reproduction, affecting 10-15 % of clinically recognized pregnancies. The cases of embryonic death can be divided into missed abortion (MA), for which the ultrasound sign of the embryo death is the absence of cardiac activity, and anembryonic pregnancy (AP) without an embryo in the gestational sac. The aim of this study was to compare the frequency of chromosomal abnormalities in extraembryonic tissues detected by conventional cytogenetic analysis of spontaneous abortions depending on the presence or absence of an embryo. This is a retrospective study of 1551 spontaneous abortions analyzed using GTG-banding from 1990 to 2022 (266 cases of AP and 1285 cases of MA). A comparative analysis of the frequency of chromosomal abnormalities and the distribution of karyotype frequencies depending on the presence of an embryo in the gestational sac was carried out. Statistical analysis was performed using a chi-square test with a p <0.05 significance level. The total frequency of chromosomal abnormalities in the study was 53.6 % (832/1551). The proportion of abnormal karyotypes in the AP and MA groups did not differ significantly and amounted to 57.1 % (152/266) and 52.9 % (680/1285) for AP and MA, respectively (p = 0.209). Sex chromosome aneuploidies and triploidies were significantly less common in the AP group than in the MA group (2.3 % (6/266) vs 6.8 % (88/1285), p = 0.005 and 4.9 % (13/266) vs 8.9 % (114/1285), p = 0.031, respectively). Tetraploidies were registered more frequently in AP compared to MA (12.4 % (33/266) vs. 8.2 % (106/1285), p = 0.031). The sex ratio among abortions with a normal karyotype was 0.54 and 0.74 for AP and MA, respectively. Thus, although the frequencies of some types of chromosomal pathology differ between AP and MA, the total frequency of chromosomal abnormalities in AP is not increased compared to MA, which indicates the need to search for the causes of AP at other levels of the genome organization, including microstructural chromosomal rearrangements, monogenic mutations, imprinting disorders, and epigenetic abnormalities.

Selection in utero against male twins in the United States early in the COVID-19 pandemic

OBJECTIVES

We aim to contribute to the literature reporting tests of selection in utero. The theory of reproductive suppression predicts that natural selection would conserve mechanisms, referred to collectively as selection in utero, that spontaneously abort fetuses unlikely to thrive as infants in the prevailing environment. Tests of this prediction include reports that women give birth to fewer than expected male twins, historically among the frailest of infants, during stressful times. The onset of the COVID-19 pandemic in the United States in Spring 2020 demonstrably stressed the population. We test the hypothesis that conception cohorts in gestation at the onset of the pandemic in the United States yielded fewer than expected live male twin births.

METHODS

We retrieved deidentified data on the universe of live births in the United States from the National Center for Health Statistics birth certificate records. We applied Box-Jenkins time-series methods to the twin secondary sex ratio computed for 77 monthly conception cohorts spanning August 2013 to December 2019 to detect outlying cohorts in gestation at the onset of the pandemic.

RESULTS

The twin secondary sex ratio fell below expected values in three conception cohorts (i.e., July, September, and October 2019, all p < .05) exposed in utero to the onset of the pandemic.

CONCLUSIONS

Our results add to prior findings consistent with selection in utero. The role of selection in utero in shaping the characteristics of live births cohorts, especially during the COVID-19 pandemic, warrants further scrutiny.

Pregnancy Loss and Cardiovascular Diseases in Women: Recent Findings and Potential Mechanisms

PURPOSE OF REVIEW

Pregnancy loss (PL) has been acknowledged by the American Heart Association as a risk factor for cardiovascular diseases (CVD) later in life. This review aims to sum up recent findings (< ~ 5 years), concerning the link between PL and CVD.

RECENT FINDINGS

The association between PL and risk of CVD increased with increasing number of PLs and is inversely correlated to maternal age, indicating that the association concerns euploid PLs. Likely mechanisms leading to PL and an increased risk of CVD include endothelial dysfunction, a pro-inflammatory state, antiphospholipid syndrome, autoimmunity, and genetic predisposition. PL as an independent risk factor for CVD constitutes an obvious gateway for a more targeted approach to future research, prevention, and treatment. Future research should clarify the following questions to which the answers are still unknown: whether PL is (a) directly causing the increased risk of CVD or (b) sharing pathophysiological mechanisms also leading to CVD.

Maternal selection of human embryos in early gestation: Insights from recurrent miscarriage

Compared to most mammals, human pregnancy is unusual in that it involves chromosomally diverse embryos, cyclical breakdown and regeneration of the uterine mucosa, and intimate integration of fetal and maternal cells at the uteroplacental interface. Not surprisingly, pregnancy often falters in early gestation. Whether these losses result in clinical miscarriages depends on the origins and impacts of chromosomal errors on fetal development and the ability of the decidualizing endometrium to engage in embryo biosensing and selection. Aneuploidy originating in oocytes during meiosis drives the age-related risk of miscarriage. By contrast, the frequency of endometrial cycles with an impaired decidual response may account for the stepwise increase in miscarriage rates with each pregnancy loss independently of maternal age. Additional physiological mechanisms operate in early gestation to ensure that most failing pregnancies are lost before vascular maternal-fetal connections are established by the end of the first trimester. Here, we summarise how investigations into the mechanisms that cause miscarriage led to new insights into the processes that govern maternal selection of human embryos in early gestation.

Genetic variation in placental insufficiency: What have we learned over time?

Genetic variation shapes placental development and function, which has long been known to impact fetal growth and pregnancy outcomes such as miscarriage or maternal pre-eclampsia. Early epidemiology studies provided evidence of a strong heritable component to these conditions with both maternal and fetal-placental genetic factors contributing. Subsequently, cytogenetic studies of the placenta and the advent of prenatal diagnosis to detect chromosomal abnormalities provided direct evidence of the importance of spontaneously arising genetic variation in the placenta, such as trisomy and uniparental disomy, drawing inferences that remain relevant to this day. Candidate gene approaches highlighted the role of genetic variation in genes influencing immune interactions at the maternal-fetal interface and angiogenic factors. More recently, the emergence of molecular techniques and in particular high-throughput technologies such as Single-Nucleotide Polymorphism (SNP) arrays, has facilitated the discovery of copy number variation and study of SNP associations with conditions related to placental insufficiency. This review integrates past and more recent knowledge to provide important insights into the role of placental function on fetal and perinatal health, as well as into the mechanisms leading to genetic variation during development.

Construction of machine learning tools to predict threatened miscarriage in the first trimester based on AEA, progesterone and β-hCG in China: a multicentre, observational, case-control study

Background

Endocannabinoid anandamide (AEA), progesterone (P4) and β-human chorionic gonadotrophin (β-hCG) are associated with the threatened miscarriage in the early stage. However, no study has investigated whether combing these three hormones could predict threatened miscarriage. Thus, we aim to establish machine learning models utilizing these three hormones to predict threatened miscarriage risk.

Methods

This is a multicentre, observational, case-control study involving 215 pregnant women. We recruited 119 normal pregnant women and 96 threatened miscarriage pregnant women including 58 women with ongoing pregnancy and 38 women with inevitable miscarriage. P4 and β-hCG levels were detected by chemiluminescence immunoassay assay. The level of AEA was tested by ultra-high-performance liquid chromatography-tandem mass spectrometry. Six predictive machine learning models were established and evaluated by the confusion matrix, area under the receiver operating characteristic (ROC) curve (AUC), accuracy and precision.

Results

The median concentration of AEA was significantly lower in the healthy pregnant women group than that in the threatened miscarriage group, while the median concentration of P4 was significantly higher in the normal pregnancy group than that in the threatened miscarriage group. Only the median level of P4 was significantly lower in the inevitable miscarriage group than that in the ongoing pregnancy group. Moreover, AEA is strongly positively correlated with threatened miscarriage, while P4 is negatively correlated with both threatened miscarriage and inevitable miscarriage. Interestingly, AEA and P4 are negatively correlated with each other. Among six models, logistic regression (LR), support vector machine (SVM) and multilayer perceptron (MLP) models obtained the AUC values of 0.75, 0.70 and 0.70, respectively; and their accuracy and precision were all above 0.60. Among these three models, the LR model showed the highest accuracy (0.65) and precision (0.70) to predict threatened miscarriage.

Conclusions

The LR model showed the highest overall predictive power, thus machine learning combined with the level of AEA, P4 and β-hCG might be a new approach to predict the threatened miscarriage risk in the near feature.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-022-05025-y.

Genomic imbalance in euploid pregnancy loss

PURPOSE

This study aims to investigate genomic imbalance in euploid products of conceptions (POCs) detected by chromosomal microarray analysis (CMA) and its association with clinical characteristics.

METHODS

In a retrospective cohort study where all women with singleton pregnancy losses underwent CMA detection of POCs, only patients with euploid POCs were included in the analysis. The clinical features were compared between those with and without a copy number variant (CNV). The pathogenic CNVs and the variant of uncertain significance (VOUS) were analyzed, and the common pathogenic CNVs and uniparental disomy (UPD) were investigated.

RESULTS

A total of 610 POCs were detected as chromosomal euploid, of which 176 were euploid with CNVs and 434 were euploid without CNVs. Regarding maternal age, gestational age, and history of pregnancy loss, no significant differences were found between the two groups. Furthermore, 104 pathogenic CNVs were identified in 93 POCs, and the deletion of 8p23.3 was found in 10 subjects. All CNVs greater than 3 Mb and 39.5% of CNVs ranging from 1 to 2 Mb were pathogenic, and only 3 CNVs < 1 Mb were pathogenic. UPD was detected in 12 POCs.

CONCLUSION

Besides aneuploidy, 15.24% pregnancy loss might have an association with pathogenic genomic imbalance, and the occurrence of genomic imbalance is not related to clinical characteristics. CNVs greater than 3 Mb in pregnancy losses have a high probability to be pathogenic, and approximately 40% of CNVs ranging from 1 to 2 Mb are pathogenic. The deletion of 8p23.3 is the most common pathogenic CVN in POCs of Chinese-Han women. The clinical significance of UPD in pregnancy loss needs further study.

Stem Cell-Based Trophoblast Models to Unravel the Genetic Causes of Human Miscarriages

Miscarriage affects approximately 15% of clinically recognized pregnancies, and 1-3% of couples experience pregnancy loss recurrently. Approximately 50-60% of miscarriages result from chromosomal abnormalities, whereas up to 60% of euploid recurrent abortions harbor variants in candidate genes. The growing number of detected genetic variants requires an investigation into their role in adverse pregnancy outcomes. Since placental defects are the main cause of first-trimester miscarriages, the purpose of this review is to provide a survey of state-of-the-art human in vitro trophoblast models that can be used for the functional assessment of specific abnormalities/variants implicated in pregnancy loss. Since 2018, when primary human trophoblast stem cells were first derived, there has been rapid growth in models of trophoblast lineage. It has been found that a proper balance between self-renewal and differentiation in trophoblast progenitors is crucial for the maintenance of pregnancy. Different responses to aneuploidy have been shown in human embryonic and extra-embryonic lineages. Stem cell-based models provide a powerful tool to explore the effect of a specific aneuploidy/variant on the fetus through placental development, which is important, from a clinical point of view, for deciding on the suitability of embryos for transfer after preimplantation genetic testing for aneuploidy.

Pregnancy loss and risk of multiple sclerosis and autoimmune neurological disorder: A nationwide cohort study

Background

The loss of one or more pregnancies before viability (i.e. pregnancy loss or miscarriage), has been linked to an increased risk of diseases later in life such as myocardial infarction and stroke. Recurrent pregnancy loss (i.e. three consecutive pregnancy losses) and multiple sclerosis have both been linked to immunological traits, which could predispose to both occurrences. The objective of the current study was to investigate if pregnancy loss is associated with later autoimmune neurological disease.

Methods

This register-based cohort study, included the Danish female population age 12 or older between 1977–2017. Women were grouped hierarchically: 0, 1, 2, ≥3 pregnancy losses, primary recurrent pregnancy loss (i.e. not preceded by a delivery), and secondary recurrent pregnancy loss (i.e. preceded by a delivery). The main outcome was multiple sclerosis and additional outcomes were amyotrophic lateral sclerosis, Guillain-Barré syndrome, and myasthenia gravis. Bayesian Poisson regression estimated incidence rate ratios [IRR] and 95% credible intervals [CI] adjusted for year, age, live births, family history of an outcome, and education.

Results

After 40,380,194 years of follow-up, multiple sclerosis was diagnosed among 7,667 out of 1,513,544 included women (0.5%), median age at diagnosis 34.2 years (IQR 27.4–41.4 years), and median age at symptom onset 31.2 years (IQR 24.8–38.2). The adjusted IRR of multiple sclerosis after 1 pregnancy loss was: 1.03 (95% CI 0.95–1.11), 2 losses: 1.02 (95% CI 0.86–1.20), ≥3 non-consecutive losses: 0.81 (95% CI 0.51–1.24), primary recurrent pregnancy loss: 1.18 (95% CI 0.84–1.60), secondary recurrent pregnancy loss: 1.16 (95% CI 0.81–1.63), as compared to women with no pregnancy losses. Seven sensitivity analyses and analyses for additional outcomes did not show significantly elevated adjusted risk estimates.

Conclusions

In this nationwide study, pregnancy loss was not significantly associated with autoimmune neurological disorder.

Preimplantation genetic testing for aneuploidy (PGT-A)-a single-center experience

PURPOSE

The aim of this study was to determine the prevalence and nature of human embryonic aneuploidy based on the preimplantation genetic testing for aneuploidy (PGT-A), the distribution of aneuploidy across the individual chromosomes, and their relationship to maternal age.

METHODS

This is a retrospective cohort study conducted at a single center. The study includes subjects who opted for PGT-A in their in vitro fertilization (IVF) cycle from 2016 to 2020. PGT-A was performed on 1501 embryos from 488 patients in 535 cycles. PGT-A was performed using NGS-based technique on Ion Torrent PGM (Life Technologies). Analysis was performed to determine the (i) frequency of the aneuploidy, (ii) the chromosome most commonly affected, (iii) relationship between maternal age and the rate of aneuploidy, and (iv) incidence of segmental aneuploidy.

RESULTS

The overall frequency of aneuploidy was observed to be 46.8%. The incidence of aneuploidy rate was ~ 28% at maternal age < 30 years which steadily increased to ~ 67% in women above 40 years. High frequency of aneuploidy was observed in chromosomes 16, 22, 21, and 15. Segmental abnormalities, involving loss or gain of chromosomal fragments, were observed at a frequency of 5.3%, and highest incidence of segmental gain was observed on the q-arm of chromosome 9.

CONCLUSION

The study provides important information regarding the frequency of the aneuploidy in IVF cohort and the most frequent chromosomal abnormality. The study further emphasizes the relationship between maternal age and aneuploidy. This study has important implications which help clinicians and genetic counselors in providing information in patient counseling.

Recurrent pregnancy loss: fewer chromosomal abnormalities in products of conception? a meta-analysis

OBJECTIVE

To compare the prevalence of chromosomal abnormalities detected in products of conception (POCs) between recurrent pregnancy loss and sporadic pregnancy loss.

METHODS

A systematic search was performed in the PubMed and Embase databases from inception to December 31, 2020. Relevant studies analysing the association between the number of pregnancy losses and the incidence of chromosomal abnormalities were included. Independent data extraction was conducted and study quality was assessed. Meta-analyses were carried out to calculate odds ratios by using fixed- or random-effects models according to statistical homogeneity.

RESULTS

A total of 8320 POCs in 19 studies were identified for the meta-analyses. The incidence of chromosomal abnormalities in sporadic pregnancy loss was significantly higher than that in recurrent pregnancy loss. In subgroup analyses, the following studies reported a high incidence of abnormal outcomes of sporadic pregnancy loss: studies with ≥ 300 samples, studies published before 2014, studies conducted in European and American countries, and studies with analyses using conventional karyotype techniques. Moreover, the incidence of chromosomal abnormalities in women with two pregnancy losses was significantly higher than that in women with three or more pregnancy losses. However, there was no difference in the distribution of abnormal types between sporadic and recurrent pregnancy loss or between two and three or more pregnancy losses.

CONCLUSIONS

The prevalence of chromosomal abnormalities detected in POCs was lower in recurrent pregnancy loss than in sporadic pregnancy loss, and decreased with an increasing number of pregnancy losses.

Pregnancy Status Is Associated with Lower Hemoglobin A1c among Nondiabetes Women in the United States from NHANES 2005-2016

BACKGROUND

It has been verified that the incidence rate of diabetes mellitus (DM) is sharply increased in pregnant female adults. However, the relationship between pregnant status and hemoglobin A1c (HbA1c) in nondiabetes women remains unclear.

METHODS

We conducted a cross-sectional study of 7762 participants in the National Health and Nutrition Examination Survey (NHANES) 2005-2016. Multivariable linear regression models were performed to evaluate the associations between pregnant status with HbA1c and serum glucose in nondiabetes women.

RESULTS

HbA1c was significantly lower in the pregnant group than in the nonpregnant group. There was a negative association between urine pregnancy test and HbA1c in all three models (model 1: β = -0.23, 95% CI: (-0.18 to -0.27); model 2: β = -0.20, 95% CI: (-0.15 to -0.24); model 3: β = -0.24, 95% CI: (-0.20 to -0.29)). In the subgroup analysis stratified by age, this negative association existed in all age subgroups (age <20: β = -0.20, 95% CI: (-0.04 to -0.27); age ≥20, <35: β = -0.24, 95% CI: (-0.20 to -0.29); age ≥35: β = -0.28, 95% CI: (-0.17, -0.39)). In the subgroup analysis stratified by race, the negative associations steadily existed in different subgroups (Mexican American:β = -0.20, 95% CI:(-0.11 to -0.29); Other Hispanic:β = -0.31, 95% CI: (-0.16 to -0.46); Non-Hispanic White: β = -0.24, 95% CI: (-0.17 to -0.31); Non-Hispanic Black: β = -0.21, 95% CI: (-0.12 to -0.31); Other races:β = -0.22, 95% CI: (-0.08 to -0.35)). On the other hand, a negative association between self-reported pregnant status and HbA1c was also found (model 1: β = -0.22, 95% CI: (-0.18 to -0.27); model 2: β = -0.19, 95% CI: (-0.15 to -0.2); model 3: β = -0.23, 95% CI: (-0.19 to -0.28)). In the subgroup analysis stratified by age, this negative association also existed in all age subgroups.

CONCLUSIONS

The study indicated that nondiabetes women with pregnant status had significantly lower HbA1c compared with those nonpregnant. Moreover, the negative associations between pregnant status and HbA1c steadily existed in subgroups stratified by age and gender.

The Role of Decidual Subpopulations in Implantation, Menstruation and Miscarriage

In each menstrual cycle, the endometrium becomes receptive to embryo implantation while preparing for tissue breakdown and repair. Both pregnancy and menstruation are dependent on spontaneous decidualization of endometrial stromal cells, a progesterone-dependent process that follows rapid, oestrogen-dependent proliferation. During the implantation window, stromal cells mount an acute stress response, which leads to the emergence of functionally distinct decidual subsets, reflecting the level of replication stress incurred during the preceding proliferative phase. Progesterone-dependent, anti-inflammatory decidual cells (DeC) form a robust matrix that accommodates the conceptus whereas pro-inflammatory, progesterone-resistant stressed and senescent decidual cells (senDeC) control tissue remodelling and breakdown. To execute these functions, each decidual subset engages innate immune cells: DeC partner with uterine natural killer (uNK) cells to eliminate senDeC, while senDeC co-opt neutrophils and macrophages to assist with tissue breakdown and repair. Thus, successful transformation of cycling endometrium into the decidua of pregnancy not only requires continuous progesterone signalling but dominance of DeC over senDeC, aided by recruitment and differentiation of circulating NK cells and bone marrow-derived decidual progenitors. We discuss how the frequency of cycles resulting in imbalanced decidual subpopulations may determine the recurrence risk of miscarriage and highlight emerging therapeutic strategies.

Embryonic lethal genetic variants and chromosomally normal pregnancy loss

OBJECTIVE

To examine whether rare damaging genetic variants are associated with chromosomally normal pregnancy loss and estimate the magnitude of the association.

DESIGN

Case-control.

SETTING

Cases were derived from a consecutive series of karyotyped losses at one New Jersey hospital. Controls were derived from the National Database for Autism Research.

PATIENT(S)

Cases comprised 19 chromosomally normal loss conceptus-parent trios. Controls comprised 547 unaffected siblings of autism case-parent trios.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

The rate of damaging variants in the exome (loss of function and missense-damaging) and the proportions of probands with at least one such variant among cases vs. controls.

RESULTS

The proportions of probands with at least one rare damaging variant were 36.8% among cases and 22.9% among controls (odds ratio, 2.0; 99% confidence interval, 0.5-7.3). No case had a variant in a known fetal anomaly gene. The proportion with variants in possibly embryonic lethal genes increased in case probands (odds ratio, 14.5; 99% confidence interval, 1.5-89.7); variants occurred in BAZ1A, FBN2, and TIMP2.

CONCLUSION(S)

Rare genetic variants in the conceptus may be a cause of chromosomally normal pregnancy loss. A larger sample is needed to estimate the magnitude of the association with precision and identify relevant biologic pathways.

Cohort Selection In Utero against Male Twins and Childhood Cancers: A Population-Based Register Study

BACKGROUND

Cancer ranks as the second leading cause of death among children ages 1 to 14 years in the United States. Previous research finds that strong cohort selection in utero against males precedes a reduction in live-born males considered frail. We examine whether such cohort selection in utero may similarly affect the frequency of childhood cancers among male live births.

METHODS

We examined 1,368 childhood cancers among males born in Sweden over 144 months, from January 1990 to December 2001, and followed to age 15 in the Swedish Cancer Registry. We retrieved the count of male twins by birth month from the Swedish Birth Registry. We applied autoregressive, integrated, moving average time-series methods to identify and control for temporal patterns in monthly childhood cancers and to evaluate robustness of results.

RESULTS

Fewer childhood cancers occur among monthly male birth cohorts with elevated selection in utero (i.e., a low count of live-born male twins). This association appears in the concurrent month (coef = 0.04; 95% CI, 0.001-0.079) as well as in the following month in which most births from the twin's conception cohort are "scheduled" to be born (coef = 0.055; 95% CI, 0.017-0.094).

CONCLUSIONS

Elevated cohort selection in utero may reduce the number of frail male gestations that would otherwise have survived to birth and received a cancer diagnosis during childhood.

IMPACT

This novel result warrants further investigation of prenatal exposures, including those at the population level, that may induce cohort selection in utero for some cancer types but not others.

Miscarriage matters: the epidemiological, physical, psychological, and economic costs of early pregnancy loss

Miscarriage is generally defined as the loss of a pregnancy before viability. An estimated 23 million miscarriages occur every year worldwide, translating to 44 pregnancy losses each minute. The pooled risk of miscarriage is 15·3% (95% CI 12·5-18·7%) of all recognised pregnancies. The population prevalence of women who have had one miscarriage is 10·8% (10·3-11·4%), two miscarriages is 1·9% (1·8-2·1%), and three or more miscarriages is 0·7% (0·5-0·8%). Risk factors for miscarriage include very young or older female age (younger than 20 years and older than 35 years), older male age (older than 40 years), very low or very high body-mass index, Black ethnicity, previous miscarriages, smoking, alcohol, stress, working night shifts, air pollution, and exposure to pesticides. The consequences of miscarriage are both physical, such as bleeding or infection, and psychological. Psychological consequences include increases in the risk of anxiety, depression, post-traumatic stress disorder, and suicide. Miscarriage, and especially recurrent miscarriage, is also a sentinel risk marker for obstetric complications, including preterm birth, fetal growth restriction, placental abruption, and stillbirth in future pregnancies, and a predictor of longer-term health problems, such as cardiovascular disease and venous thromboembolism. The costs of miscarriage affect individuals, health-care systems, and society. The short-term national economic cost of miscarriage is estimated to be £471 million per year in the UK. As recurrent miscarriage is a sentinel marker for various obstetric risks in future pregnancies, women should receive care in preconception and obstetric clinics specialising in patients at high risk. As psychological morbidity is common after pregnancy loss, effective screening instruments and treatment options for mental health consequences of miscarriage need to be available. We recommend that miscarriage data are gathered and reported to facilitate comparison of rates among countries, to accelerate research, and to improve patient care and policy development.

Could PGT-A pick up true abnormalities that have clinical relevance? Retrospective analysis of 1043 embryos

OBJECTIVE

To determine whether preimplantation genetic testing for aneuploidy (PGT-A) could pick up true abnormalities that have clinical relevance.

MATERIALS AND METHODS

This was a retrospective cohort study of patients who underwent in vitro fertilization with PGT-A from 2015 to 2017. We evaluated the associations of aneuploidy and mosaicism with maternal age, the chromosome abnormalities present in individual chromosomes, and the effect of embryo sex on the proportion of each type of error in the four chromosomes most frequently affected.

RESULT(S)

A total of 1043 embryos from 255 patients (mean maternal age = 39 ± 4 years) were included in the initial analysis. Of these, 36% (377/1043) were euploid, 47% (487/1043) were aneuploid, 13% (140/1043) contained mosaicism, and 4% (39/1043) gave no result. We excluded the 39 embryos with no result; thus, 1004 embryos were included in the analysis. Increased aneuploidy was associated with increased maternal age, but the rate of embryo mosaicism was not. A combined analysis of aneuploidy with noncomplex abnormalities and mosaicism showed that chromosomes 22, 21, 16, and 15 were the most frequently involved. Chromosome 22 showed the highest proportion of mosaicism and chromosome 15 showed the highest proportion of aneuploidy. When we included embryo sex in the analysis, embryo sex was associated with these chromosome errors in the most susceptible chromosome, 22.

CONCLUSION(S)

PGT-A showed that chromosomes 22, 21, 16, and 15 were the most frequently involved among common chromosome abnormalities, comparable with those of published data analyzed from spontaneous abortion. This result suggested that PGT-A could pick up abnormalities that have clinical relevance to spontaneous abortion. Moreover, we identified a role of embryo sex in these chromosomal errors on chromosome 22.

Chromosomal Aneuploidy Associated With Clinical Characteristics of Pregnancy Loss

Objective

Embryonic aneuploidy is found in about half of sporadic pregnancy losses and the associations between the chromosomal aneuploidy and clinical characteristics of pregnancy loss remain unclear. The aims of this study were to evaluate the associations between chromosomal aneuploidy of products of conception (POC) and clinical features of pregnancy loss.

Methods

We conducted a retrospective cohort study including 1,102 women experienced singleton pregnancy loss and underwent chromosomal microarray analysis (CMA) detection of POC in our hospital. The results of molecular karyotypes and clinical features including maternal age, history of pregnancy loss, gestational age, vaginal bleeding and ultrasonographic findings were extracted from the medical records. χ² test was used to compare categorical data between groups.

Results

631 (57.26%) POC specimens were detected to be chromosomal aneuploidy. Aneuploid rates were significantly higher in women >35 years (P < 0.001) and pregnancy loss <11 gestational weeks (P = 0.044), but the rates of sex chromosome abnormalities and triploid were significantly higher in women ≤35 years (P < 0.001, P = 0.002) and the rates of viable autosomal trisomy and sex chromosome abnormalities were significantly high in those women with pregnancy loss ≥11 weeks (P < 0.001, P < 0.001). Aneuploid rate was overall similar between the sporadic and the recurrent pregnancy loss (RPL) (P = 0.404), but the rate of sex chromosome abnormalities was higher in women with sporadic pregnancy loss (P = 0.03). Aneuploid rates were higher in subjects with yolk sac or embryo than in those without (P < 0.001 and P = 0.001).

Conclusion

Advanced maternal age is mainly associated with autosomal trisomy, while sex chromosome abnormalities and triploid might be more likely to occur in younger women. Aneuploidy rates might be no association with previous pregnancy loss except for sex chromosome abnormalities. Pregnancy loss without yolk sac or embryo might be less related to embryonic aneuploidy, and other factors should be emphasized.

Recurrent pregnancy loss

Recurrent pregnancy loss is a distressing pregnancy disorder experienced by ~2.5% of women trying to conceive. Recurrent pregnancy loss is defined as the failure of two or more clinically recognized pregnancies before 20-24 weeks of gestation and includes embryonic and fetal losses. The diagnosis of an early pregnancy loss is relatively straightforward, although progress in predicting and preventing recurrent pregnancy loss has been hampered by a lack of standardized definitions, the uncertainties surrounding the pathogenesis and the highly variable clinical presentation. The prognosis for couples with recurrent pregnancy loss is generally good, although the likelihood of a successful pregnancy depends on maternal age and the number of previous losses. Recurrent pregnancy loss can be caused by chromosomal errors, anatomical uterine defects, autoimmune disorders and endometrial dysfunction. Available treatments target the putative risk factors of pregnancy loss, although the effectiveness of many medical interventions is controversial. Regardless of the underlying aetiology, couples require accurate information on their chances of having a baby and appropriate support should be offered to reduce the psychological burden associated with multiple miscarriages. Future research must investigate the pathogenesis of recurrent pregnancy loss and evaluate novel diagnostic tests and treatments in adequately powered clinical trials.

Copy number analysis of meiotic and postzygotic mitotic aneuploidies in trophectoderm cells biopsied at the blastocyst stage and arrested embryos

Preimplantation genetic testing for aneuploidy (PGT-A) by copy number analysis is now widely used to select euploid embryos for transfer. Whole or partial chromosome aneuploidy can arise in meiosis, predominantly female meiosis, or in the postzygotic, mitotic divisions during cleavage and blastocyst formation, resulting in chromosome mosaicism. Meiotic aneuploidies are almost always lethal, however, the clinical significance of mitotic aneuploidies detected by PGT-A is not fully understood and healthy live births have been reported following transfer of mosaic embryos. Here, we used single nucleotide polymorphism genotyping of both polar bodies and embryo samples to identify meiotic aneuploidies and compared copy number changes for meiotic and presumed mitotic aneuploidies in trophectoderm cells biopsied at the blastocyst stage and arrested embryos. PGT-A detected corresponding full copy number changes (≥70%) for 36/37 (97%) maternal meiotic aneuploidies. The number of presumed mitotic copy number changes detected exceeded those of meiotic origin. Although mainly in the mosaic range, some of these mitotic aneuploidies had copy number changes ≥70% and would have been identified as full aneuploidies. Interestingly, many arrested embryos had multiple mitotic aneuploidies across a broad range of copy number changes, which may have arisen through tripolar spindle and other mitotic abnormalities.

Sporadic pregnancy loss and recurrent miscarriage

Progesterone is essential for the maintenance of pregnancy, and progesterone deficiency is associated with miscarriage. The subject of whether progesterone supplementation in early pregnancy can prevent miscarriage has been a long-standing research question and has been investigated and debated in the medical literature for over 70 years. During this time, several different progestogens have been synthesised and tested for the prevention of miscarriage. In this chapter, we describe the prior evidence alongside the latest research using micronized natural progesterone as well as synthetic progestogens, which were used to treat both recurrent and threatened miscarriage. The totality of evidence indicates that women with a past history of miscarriage who present with bleeding in early pregnancy may benefit from the use of vaginal micronized progesterone. The clinical implications of the findings are discussed.

Pregnancy loss is associated with type 2 diabetes: a nationwide case-control study

AIMS/HYPOTHESIS

Type 2 diabetes is killing more people than ever, and early-life predictors remain critical for the development of effective preventive strategies. Pregnancy loss is a common event associated with later atherosclerotic disease and ischaemic heart failure and might constitute a predictor for type 2 diabetes. The objective of this study was to investigate whether pregnancy loss is associated with later development of type 2 diabetes.

METHODS

Using a Danish nationwide cohort, we identified all women born from 1957 through to 1997 and who had a diagnosis of type 2 diabetes during the period 1977 to 2017. The women were matched 1:10 on year of birth and educational level to women without diabetes in the general Danish population. Conditional logistic regression models provided odds ratios for type 2 diabetes with different numbers of pregnancy losses.

RESULTS

We identified 24,774 women with type 2 diabetes and selected 247,740 controls without diabetes. Women who had ever been pregnant (ever-pregnant women) with 1, 2 and ≥ 3 pregnancy losses had ORs of type 2 diabetes of 1.18 (95% CI 1.13, 1.23), 1.38 (95% CI 1.27, 1.49) and 1.71 (95% CI 1.53, 1.92) compared with ever-pregnant women with no pregnancy losses, respectively. Women who never achieved a pregnancy had an OR of type 2 diabetes of 1.56 (95% CI 1.51, 1.61) compared with ever-pregnant women with any number of losses. Similar results were found after adjustment for obesity and gestational diabetes.

CONCLUSIONS/INTERPRETATION

We found a significant and consistent association between pregnancy loss and later type 2 diabetes that increased with increasing number of losses. Thus, pregnancy loss and recurrent pregnancy loss are significant risk factors for later type 2 diabetes. Future studies should explore whether this association is due to common background factors or whether prediabetic metabolic conditions are responsible for this association. Graphical abstract.

The first glimpse of the endometrial microbiota in early pregnancy

Investigation of the microbial community in the female reproductive tract with the use of sequencing techniques has revealed that endometrial samples obtained through a transvaginal catheter are dominated by Lactobacillus species. Dysbiotic changes in the endometrial microbiota may be associated with implantation failure or early spontaneous abortion in patients who undergo assisted reproductive technology treatment. Whether or not there is an endometrial microbiota in early pregnancy is unknown. Herein we describe, the human endometrial microbiota in a patient who subsequently had an 8th week spontaneous clinical miscarriage with euploid embryos in the next cycle and, for the first time, during a successful pregnancy in which the endometrial fluid was sampled at 4 weeks of gestation. The microbial profile found on the endometrial sample before the spontaneous abortion had higher bacterial diversity and lower Lactobacillus abundance than the endometrial fluid from the healthy pregnancy. Functional metagenomics detected different Lactobacillus species between the 2 samples. Lactobacillus crispatus was present in the endometrium before the spontaneous abortion, as were other bacteria involved in dysbiosis, which had an unstable functional pattern characterized by transposases and insertion elements. Lactobacillus iners was the most prevalent microbe found in the endometrium during early pregnancy; its presence was associated with defense mechanisms and basal functions. These novel observations prompt future investigations to understand the potential implications of microbiology on healthy and pathologic human pregnancy.

Early pregnancy loss: the default outcome for fertilized human oocytes

Early pregnancy loss is by far the most frequent outcome of human reproduction. It occurs when despite the timely interaction of gametes and initiation of embryogenesis and implantation of the conceptus, pregnancy continuance fails. From a clinical perspective, early pregnancy loss represents a neglected but relevant issue because of the high incidence, the evolving and yet not fully elucidated mechanism, the possible association with other relevant medical conditions, and the potential psychological sequelae. Our growing understanding of the dialog established between the embryo and the endometrium provides new insights into the etiology of pregnancy loss. Aneuploidies as a cause of early pregnancy loss are known for a long time, but there is now evidence that endometrium is not a passive player. An active selection aimed at impeding implantation of unhealthy embryos actually occurs at the endometrial interface. The concept of selectivity is substituting the one of mere receptivity.

Chromosome Missegregation in Single Human Oocytes Is Related to the Age and Gene Expression Profile

The growing trend for women to postpone childbearing has resulted in a dramatic increase in the incidence of aneuploid pregnancies. Despite the importance to human reproductive health, the events precipitating female age-related meiotic errors are poorly understood. To gain new insight into the molecular basis of age-related chromosome missegregation in human oocytes, we combined the transcriptome profiles of twenty single oocytes (derived from females divided into two groups according to age <35 and ≥35 years) with their chromosome status obtained by array comparative genomic hybridization (aCGH). Furthermore, we compared the transcription profile of the single oocyte with the surrounding cumulus cells (CCs). RNA-seq data showed differences in gene expression between young and old oocytes. Dysregulated genes play a role in important biological processes such as gene transcription regulation, cytoskeleton organization, pathways related to RNA maturation and translation. The comparison of the transcription profile of the oocyte and the corresponding CCs highlighted the differential expression of genes belonging to the G protein-coupled receptor superfamily. Finally, we detected the loss of a X chromosome in two oocytes derived from women belonging to the ≥35 years age group. These aneuploidies may be caused by the detriment of REEP4, an endoplasmic reticulum protein, in women aged ≥35 years. Here we gained new insight into the complex regulatory circuit between the oocyte and the surrounding CCs and uncovered a new putative molecular basis of age-related chromosome missegregation in human oocytes.

Collective Optimism and Selection Against Male Twins in Utero

Scholarly literature claims that health declines in populations when optimism about investing in the future wanes. This claim leads us to describe collective optimism as a predictor of selection in utero. Based on the literature, we argue that the incidence of suicide gauges collective optimism in a population and therefore willingness to invest in the future. Using monthly data from Sweden for the years 1973-2016, we test the hypothesis that the incidence of suicide among women of child-bearing age correlates inversely with male twin births, an indicator of biological investment in high-risk gestations. We find that, as predicted by our theory, the incidence of suicide at month t varies inversely with the ratio of twin to singleton male births at month t + 3. Our results illustrate the likely sensitivity of selection in utero to change in the social environment and so the potential for viewing collective optimism as a component of public health infrastructure.

Recurrent pregnancy loss is associated with a pro-senescent decidual response during the peri-implantation window

During the implantation window, the endometrium becomes poised to transition to a pregnant state, a process driven by differentiation of stromal cells into decidual cells (DC). Perturbations in this process, termed decidualization, leads to breakdown of the feto-maternal interface and miscarriage, but the underlying mechanisms are poorly understood. Here, we reconstructed the decidual pathway at single-cell level in vitro and demonstrate that stromal cells first mount an acute stress response before emerging as DC or senescent DC (snDC). In the absence of immune cell-mediated clearance of snDC, secondary senescence transforms DC into progesterone-resistant cells that abundantly express extracellular matrix remodelling factors. Additional single-cell analysis of midluteal endometrium identified DIO2 and SCARA5 as marker genes of a diverging decidual response in vivo. Finally, we report a conspicuous link between a pro-senescent decidual response in peri-implantation endometrium and recurrent pregnancy loss, suggesting that pre-pregnancy screening and intervention may reduce the burden of miscarriage.

Impact of sitagliptin on endometrial mesenchymal stem-like progenitor cells: A randomised, double-blind placebo-controlled feasibility trial

BACKGROUND

Recurrent pregnancy loss (RPL) is associated with the loss of endometrial mesenchymal stem-like progenitor cells (eMSC). DPP4 inhibitors may increase homing and engraftment of bone marrow-derived cells to sites of tissue injury. Here, we evaluated the effect of the DPP4 inhibitor sitagliptin on eMSC in women with RPL, determined the impact on endometrial decidualization, and assessed the feasibility of a full-scale clinical trial.

METHODS

A double-blind, randomised, placebo-controlled feasibility trial on women aged 18 to 42 years with a history of 3 or more miscarriages, regular menstrual cycles, and no contraindications to sitagliptin. Thirty-eight subjects were randomised to either 100 mg sitagliptin daily for 3 consecutive cycles or identical placebo capsules. Computer generated, permuted block randomisation was used to allocate treatment packs. Colony forming unit (CFU) assays were used to quantify eMSC in midluteal endometrial biopsies. The primary outcome measure was CFU counts. Secondary outcome measures were endometrial thickness, study acceptability, and first pregnancy outcome within 12 months following the study. Tissue samples were subjected to explorative investigations.

FINDINGS

CFU counts following sitagliptin were higher compared to placebo only when adjusted for baseline CFU counts and age (RR: 1.52, 95% CI: 1.32-1.75, P<0.01). The change in CFU count was 1.68 in the sitagliptin group and 1.08 in the placebo group. Trial recruitment, acceptability, and drug compliance were high. There were no serious adverse events. Explorative investigations showed that sitagliptin inhibits the expression of DIO2, a marker gene of senescent decidual cells.

INTERPRETATION

Sitagliptin increases eMSCs and decreases decidual senescence. A large-scale clinical trial evaluating the impact of preconception sitagliptin treatment on pregnancy outcome in RPL is feasible and warranted.

FUNDING

Tommy's Baby Charity.

CLINICAL TRIAL REGISTRATION

EU Clinical Trials Register no. 2016-001120-54.

Pregnancy Loss and Cancer Risk: A Nationwide Observational Study

BACKGROUND

Cancer is the second leading cause of death worldwide. Few studies have investigated if recurrent pregnancy loss is associated with an increased risk of cancer. We aimed to assess whether pregnancy loss is associated with later cancer development.

METHODS

We identified all invasive cancers after age 40, among all Danish women born between January 1957 and December 1972, ensuring a full reproductive history. Cases were matched by birth year 1:10 to cancer-free controls. Women were followed until the end of 2017. The number of pregnancy losses (miscarriages or still births) was correlated to long-term cancer risk using conditional logistic regression, providing odds ratios for specific cancers with different numbers of pregnancy losses, all adjusted for age, education, and other potential confounders.

FINDINGS

The study included 28,785 women with cancer (mean age 48.7 [SD 5.0]) and 283,294 matched controls (mean age 48.6 [SD 5.0]). We found no overall association between pregnancy loss and later development of 11 site-specific types of cancer or cancer overall. Taking the sequence of pregnancy losses into account, primary recurrent pregnancy loss (three consecutive pregnancy losses without prior live birth) was associated with later overall cancer by an odds ratio of 1.27 (1.04-1.56). Secondary recurrent pregnancy loss showed no association to cancer.

INTERPRETATION

Pregnancy loss was not associated with later cancer development. Women with primary recurrent pregnancy loss had a borderline significant association to later cancer overall, this may be a chance finding.

FUNDING

Ole Kirk's Foundation and Copenhagen University Hospital Rigshospitalet's Research Grant.

The significance of the placental genome and methylome in fetal and maternal health

The placenta is a crucial organ for supporting a healthy pregnancy, and defective development or function of the placenta is implicated in a number of complications of pregnancy that affect both maternal and fetal health, including maternal preeclampsia, fetal growth restriction, and spontaneous preterm birth. In this review, we highlight the role of the placental genome in mediating fetal and maternal health by discussing the impact of a variety of genetic alterations, from large whole-chromosome aneuploidies to single-nucleotide variants, on placental development and function. We also discuss the placental methylome in relation to its potential applications for refining diagnosis, predicting pathology, and identifying genetic variants with potential functional significance. We conclude that understanding the influence of the placental genome on common placental-mediated pathologies is critical to improving perinatal health outcomes.

Maternal age, history of miscarriage, and embryonic/fetal size are associated with cytogenetic results of spontaneous early miscarriages

PURPOSE

To clarify the associations of the maternal age, history of miscarriage, and embryonic/fetal size at miscarriage with the frequencies and profiles of cytogenetic abnormalities detected in spontaneous early miscarriages.

METHODS

Miscarriages before 12 weeks of gestation, whose karyotypes were evaluated by G-banding between May 1, 2005, and May 31, 2017, were included in this study. The relationships between their karyotypes and clinical findings were assessed using trend or chi-square/Fisher's exact tests and multivariate logistic analyses.

RESULTS

Three hundred of 364 miscarriage specimens (82.4%) had abnormal karyotypes. An older maternal age was significantly associated with the frequency of abnormal karyotype (p_trend < 0.001), particularly autosomal non-viable and viable trisomies (p_trend 0.001 and 0.025, respectively). Women with ≥ 2 previous miscarriages had a significantly lower possibility of miscarriages with abnormal karyotype than women with < 2 previous miscarriages (adjusted odds ratio [aOR], 0.48; 95% confidence interval [95% CI], 0.27-0.85). Although viable trisomy was observed more frequently in proportion to the increase in embryonic/fetal size at miscarriage (p_trend < 0.001), non-viable trisomy was observed more frequently in miscarriages with an embryonic/fetal size < 10 mm (aOR, 2.41; 95% CI, 1.27-4.58), but less frequently in miscarriages with an embryonic/fetal size ≥ 20 mm (aOR, 0.01; 95% CI, 0.00-0.07) than in anembryonic miscarriages.

CONCLUSIONS

The maternal age, history of miscarriage, and embryonic/fetal size at miscarriage may be independently associated with the frequencies or profiles of cytogenetic abnormalities in early miscarriages.