Genetic innovations and our understanding of stillbirth

Prenatal aneuploidy screening and its impact on stillbirth etiology evaluation

BACKGROUND

Stillbirth impacts 1% of all pregnancies in the USA with the underlying cause often remaining unknown. The objective of this study was to identify if prenatal aneuploidy screening impacted patient agreement to stillbirth evaluation.

METHODS

We performed a retrospective cohort study of patients with a singleton stillbirth after 20 weeks of gestation between October 2017 and December 2021. Demographics and stillbirth evaluation were collected for all patients. Multivariable logistic regression was performed adjusting for variables that were significant in univariate analysis.

RESULTS

A total of 81 persons experienced stillbirth during the study period. Approximately 59.3% of patients had prenatal aneuploidy screening: 39.5% integrated screening, 37.5% non-invasive prenatal testing (NIPT), and 22.9% quad screen. Prenatal genetic screening did not significantly impact patient agreement to placental pathology, serum laboratory evaluation, or fetal autopsy. Patients with NIPT were less likely to have genetic testing sent at the time of stillbirth compared to those with another aneuploidy screening (aOR 0.27, 95% CI 0.07-0.99).

CONCLUSIONS

Prenatal aneuploidy screening was not associated with patient acceptance of stillbirth evaluation. However, patients with NIPT were less likely to pursue further genetic testing during stillbirth evaluation, so further education regarding the benefit of karyotype and microarray should be included in patient counseling.

Placental Pathology Findings in Unexplained Pregnancy Losses

There are approximately 5 million pregnancies per year in the USA, with 1 million ending in miscarriage (a loss occurring prior to 20 weeks of gestation) and over 20,000 ending in stillbirth at or beyond 20 weeks of gestation. As many as 50% of these losses are unexplained. Our objective was to evaluate the effect of expanding the placental pathology diagnostic categories to include the explicit categories of (1) dysmorphic chorionic villi and (2) small placenta in examining previously unexplained losses. Using a clinical database of 1256 previously unexplained losses at 6-43 weeks of gestation, the most prevalent abnormality associated with each loss was determined through examination of its placental pathology slides. Of 1256 cases analyzed from 922 patients, there were 878 (69.9%) miscarriages and 378 (30.1%) antepartum stillbirths. We determined the pathologic diagnoses for 1150/1256 (91.6%) of the entire series, 777/878 (88.5%) of the miscarriages (< 20 weeks' gestation), and 373/378 (98.7%) of the stillbirths (≥ 20 weeks' gestation). The most common pathologic feature observed in unexplained miscarriages was dysmorphic chorionic villi (757 cases; 86.2%), a marker associated with genetic abnormalities. The most common pathologic feature observed in unexplained stillbirths was a small placenta (128 cases; 33.9%). Our classification system reinforced the utility of placental examination for elucidating potential mechanisms behind pregnancy loss. The improved rate of diagnosis appeared to be the result of filling a gap in previous pregnancy loss classification systems via inclusion of the categories of dysmorphic chorionic villi and small placenta.

Genomics of stillbirth

Stillbirth, defined as fetal death at 20 weeks gestation or later, is a devastating pregnancy outcome affecting 1 in 175 pregnancies in the United States. Although efforts to understand the etiology of stillbirth have expanded, 25 % of cases remain unexplained and some cases previously thought to be explained may have additional unknown causative factors. Determining an etiology for stillbirth is important for clinical management and for grieving families to obtain closure, to find meaning, and to understand recurrence risks. However, the evaluation of stillbirth is not completed uniformly despite American College of Obstetrics and Gynecology (ACOG) guidelines and stillbirth data is frequently incomplete due to lack of genomic analysis, fetal autopsy, and placental pathology. Karyotype and chromosomal microarray have been the gold standard in genetic analysis in perinatal medicine for many years, but next generation sequencing holds promise towards improving diagnostic yields and providing clarity for both clinicians and patients.

Sequential application of copy number variation sequencing and quantitative fluorescence polymerase chain reaction in genetic analysis of miscarriage and stillbirth

BACKGROUND

Copy number variation sequencing (CNV-seq) could detect most chromosomal abnormalities except polyploidy, and quantitative fluorescence polymerase chain reaction (QF-PCR) is a supplementary method to CNV-seq in triploid detection. This study aimed to evaluate the feasibility of sequential application of CNV-seq and QF-PCR in genetic analysis of miscarriage and stillbirth.

METHODS

A total of 261 fetal specimens were analyzed by CNV-seq, and QF-PCR was only further performed for samples with normal female karyotype identified by CNV-seq. Cost and turnaround time (TAT) was analyzed for sequential detection strategy. Subgroup analysis and logistic regression were carried out to evaluate the relationship between clinical characteristics (maternal age, gestational age, and number of pregnancy losses) and the occurrence of chromosomal abnormalities.

RESULTS

Abnormal results were obtained in 120 of 261 (45.98%) cases. Aneuploidy was the most common abnormality (37.55%), followed by triploidy (4.98%) and pathogenic copy number variations (pCNVs) (3.45%). CNV-seq could detect the triploidy with male karyotype, and QF-PCR could further identify the remaining triploidy with female karyotype. In this study, we found more male triploidies than female triploidies. With the same ability in chromosomal abnormalities detection, the cost of sequential strategy decreased by 17.35% compared with combined strategy. In subgroup analysis, significant difference was found in the frequency of total chromosomal abnormalities between early abortion group and late abortion group. Results of logistic regression showed a trend that pregnant women with advanced age, first-time abortion, and abortion earlier than 12 weeks were more likely to detect chromosomal aberrations in their products of conception.

CONCLUSION

Sequential application of CNV-seq and QF-PCR is an economic and practical strategy to identify chromosomal abnormalities in fetal tissue.

Familial aggregation of stillbirth: A pedigree analysis of a matched case-control study

OBJECTIVE

To determine whether stillbirth aggregates in families and quantify its familial risk using extended pedigrees.

DESIGN

State-wide matched case-control study.

SETTING

Utah, United States.

POPULATION

Stillbirth cases (n = 9404) and live birth controls (18 808) between 1978 and 2019.

METHODS

Using the Utah Population Database, a population-based genealogical resource linked with state fetal death and birth records, we identified high-risk pedigrees with excess familial aggregation of stillbirth using the Familial Standardised Incidence Ratio (FSIR). Stillbirth odds ratio (OR) for first-degree relatives (FDR), second-degree relatives (SDR) and third-degree relatives (TDR) of parents with a stillbirth (affected) and live birth (unaffected) were estimated using logistic regression models.

MAIN OUTCOME MEASURES

Familial aggregation estimated using FSIR, and stillbirth OR estimated for FDR, SDR and TDR of affected and unaffected parents using logistic regression models.

RESULTS

We identified 390 high-risk pedigrees with evidence for excess familial aggregation (FSIR ≥2.00; P-value <0.05). FDRs, SDRs and TDRs of affected parents had 1.14-fold (95% confidence interval [CI]: 1.04-1.26), 1.22-fold (95% CI 1.11-1.33) and 1.15-fold (95% CI 1.08-1.21) higher stillbirth odds compared with FDRs, SDRs and TDRs of unaffected parents, respectively. Parental sex-specific analyses showed male FDRs, SDRs and TDRs of affected fathers had 1.22-fold (95% CI 1.02-1.47), 1.38-fold (95% CI 1.17-1.62) and 1.17-fold (95% CI 1.05-1.30) higher stillbirth odds compared with those of unaffected fathers, respectively. FDRs, SDRs and TDRs of affected mothers had 1.12-fold (95% CI 0.98-1.28), 1.09-fold (95% CI 0.96-1.24) and 1.15-fold (95% CI 1.06-1.24) higher stillbirth odds compared with those of unaffected mothers, respectively.

CONCLUSIONS

We provide evidence for familial aggregation of stillbirth. Our findings warrant investigation into genes associated with stillbirth and underscore the need to design large-scale studies to determine the genetic architecture of stillbirth.

Cardiac ion channels associated with unexplained stillbirth - an immunohistochemical study

OBJECTIVES

Despite the use of post-mortem investigations, approximately 20% of stillbirths remain unexplained. Cardiac ion channelopathies have been identified as a cause of death in Sudden Infant Death Syndrome (SIDS) and could be associated with unexplained stillbirths. This study aimed to understand if the expression or localisation of cardiac ion channels associated with channelopathies were altered in cases of unexplained stillbirths.

METHODS

A case control study was conducted using formalin-fixed cardiac tissue from 20 cases of unexplained stillbirth and a control group of 20 cases of stillbirths from intrapartum hypoxia. 4 µm tissue sections were stained using haematoxylin and eosin, Masson's trichrome (MT) and Elastic van Gieson (EVG). Immunohistochemistry (IHC) was performed using antibodies against CACNA1G, KCNJ2, KCNQ1, KCNH2 and KCNE1. The cardiac conduction system in samples stained with MT and EVG could not be identified. Therefore, the levels of immunoperoxidase staining were quantified using QuPath software.

RESULTS

The nuclear-cytoplasmic ratio of sections stained with haematoxylin and eosin was higher for the hypoxia group (hypoxia median 0.13 vs. 0.04 unexplained, p < 0.001). CACNA1G (unexplained median 0.26 vs. hypoxia 0.30, p=0.009) and KCNJ2 (unexplained median 0.35 vs. hypoxia 0.41, p=0.001) had lower staining intensity in the unexplained stillbirth group. There were no statistically significant differences in the staining intensity of KCNQ1, KCNH2 and KCNE1.

CONCLUSIONS

Two ion channels associated with channelopathies demonstrated lower levels of expression in cases of unexplained stillbirth. Further genetic studies using human tissue should be performed to understand the association between channelopathies and otherwise unexplained stillbirths.

Knowledge and attitude of pregnant women in the Kingdom of Saudi Arabia toward Noninvasive prenatal testing: A single center study

Background

Noninvasive prenatal testing (NIPT) is a screening tool for chromosomal aneuploidies. Prior knowledge of NIPT is an inherent factor in the decision‐making process. We assessed the knowledge and attitude of pregnant women related to prenatal testing with a particular focus on NIPT.

Methods

A prospective cross‐sectional study, using a culturally validated questionnaire, was conducted with 342 pregnant women of whom 74.9% consented for prenatal screening. Mean age and gestational weeks ± standard deviation was 31 ± 5 and 26 ± 11, respectively.

Results

A positive/very positive attitude was observed to ultrasound, followed by FCT, NIPT, and lastly to CVS. More than half of the participants (56.1%) had no previous knowledge of NIPT. A reaching significance association was detected between education and knowledge of NIPT. Significant association was detected between risk for aneuploidy and knowledge of NIPT. The majority (74%) indicated their willingness to perform the test. The effect and value of society on the pregnant women to make a decision regarding NIPT was negligible.

Conclusion

The pregnant women in the current study displayed a lack of knowledge and awareness regarding prenatal screening, particularly the NIPT. We recommend that pregnant women receive adequate counseling regarding prenatal screening to increase their awareness and knowledge of prenatal testing, including NIPT.

Impact of parental relatedness on reproductive outcomes among the Old Order Amish of Lancaster County

Genetically isolated populations that arise due to recent bottleneck events have reduced genetic variation reflecting the common set of founders. Increased genetic relatedness among members of isolated populations puts them at increased risk for some recessive disorders that are rare in outbred populations. To assess the burden on reproductive health, we compared frequencies of adverse reproductive outcomes between Amish couples who were both heterozygous carriers of a highly penetrant pathogenic or likely pathogenic variant and noncarrier couples from the same Amish community. In addition, we evaluated whether overall genetic relatedness of parents was associated with reproductive outcomes. Of the 1824 couples included in our study, 11.1% were at risk of producing a child with an autosomal recessive disorder. Carrier couples reported a lower number of miscarriages compared to noncarrier couples (p = 0.02), although the number of stillbirths (p = 0.3), live births (p = 0.9), and number of pregnancies (p = 0.9) did not differ significantly between groups. In contrast, higher overall relatedness between spouses was positively correlated with number of live births (p < 0.0001), pregnancies (p < 0.0001), and stillbirths (p = 0.03), although not with the number of miscarriages (p = 0.4). These results highlight a complex association between relatedness of parents and reproductive health outcomes in this community.

Extreme Heat and Pregnancy Outcomes: A Scoping Review of the Epidemiological Evidence

Background: Extreme heat caused by climate change is a major public health concern, disproportionately affecting poor and racialized communities. Gestational heat exposure is a well-established teratogen in animal studies, with a growing body of literature suggesting human pregnancies are similarly at risk. Characterization of extreme heat as a pregnancy risk is problematic due to nonstandard definitions of heat waves, and variable study designs. To better focus future research in this area, we conducted a scoping review to assess the effects of extreme heat on pregnancy outcomes. Methods: A scoping review of epidemiological studies investigating gestational heat-exposure and published 2010 and 2020, was conducted with an emphasis on study design, gestational windows of sensitivity, adverse pregnancy outcomes and characterization of environmental temperatures. Results: A sample of 84 studies was identified, predominantly set in high-income countries. Preterm birth, birthweight, congenital anomalies and stillbirth were the most common pregnancy outcome variables. Studies reported race/ethnicity and/or socioeconomic variables, however these were not always emphasized in the analysis. Conclusion: Use of precise temperature data by most studies avoided pitfalls of imprecise, regional definitions of heat waves, however inconsistent study design, and exposure windows are a significant challenge to systematic evaluation of this literature. Despite the high risk of extreme heat events and limited mitigation strategies in the global south, there is a significant gap in the epidemiological literature from these regions. Greater consistency in study design and exposure windows would enhance the rigor of this field.

A Systematic Review to Guide Future Efforts in the Determination of Genetic Causes of Pregnancy Loss

Background: Pregnancy loss is the most common obstetric complication occurring in almost 30% of conceptions overall and in 12–14% of clinically recognized pregnancies. Pregnancy loss has strong genetic underpinnings, and despite this consensus, our understanding of its genetic causes remains limited. We conducted a systematic review of genetic factors in pregnancy loss to identify strategies to guide future research.

Methods: To synthesize data from population-based association studies on genetics of pregnancy loss, we searched PubMed for relevant articles published between 01/01/2000-01/01/2020. We excluded review articles, case studies, studies with limited sample sizes to detect associations (N &lt; 4), descriptive studies, commentaries, and studies with non-genetic etiologies. Studies were classified based on developmental periods in gestation to synthesize data across various developmental epochs.

Results: Our search yielded 580 potential titles with 107 (18%) eligible after title/abstract review. Of these, 54 (50%) were selected for systematic review after full-text review. These studies examined either early pregnancy loss (n = 9 [17%]), pregnancy loss &gt;20 weeks' gestation (n = 10 [18%]), recurrent pregnancy loss (n = 32 [59%]), unclassified pregnancy loss (n = 3 [4%]) as their primary outcomes. Multiple genetic pathways that are essential for embryonic/fetal survival as well as human development were identified.

Conclusion: Several genetic pathways may play a role in pregnancy loss across developmental periods in gestation. Systematic evaluation of pregnancy loss across developmental epochs, utilizing whole genome sequencing in families may further elucidate causal genetic mechanisms and identify other pathways critical for embryonic/fetal survival.

Recurrent Pregnancy Loss and Concealed Long-QT Syndrome

Background

Recurrent pregnancy loss affects 1% to 2% of couples attempting childbirth. A large fraction of all cases remains idiopathic, which warrants research into monogenic causes of this distressing disorder.

Methods and Results

We investigated a nonconsanguineous Estonian family who had experienced 5 live births, intersected by 3 early pregnancy losses, and 6 fetal deaths, 3 of which occurred during the second trimester. No fetal malformations were described at the autopsies performed in 3 of 6 cases of fetal death. Parental and fetal chromosomal abnormalities (including submicroscopic) and maternal risk factors were excluded. Material for genetic testing was available from 4 miscarried cases (gestational weeks 11, 14, 17, and 18). Exome sequencing in 3 pregnancy losses and the mother identified no rare variants explicitly shared by the miscarried conceptuses. However, the mother and 2 pregnancy losses carried a heterozygous nonsynonymous variant, resulting in p.Val173Asp (rs199472695) in the ion channel gene KCNQ1. It is expressed not only in heart, where mutations cause type 1 long‐QT syndrome, but also in other tissues, including uterus. The p.Val173Asp variant has been previously identified in a patient with type 1 long‐QT syndrome, but not reported in the Genome Aggregation Database. With heterologous expression in CHO cells, our in vitro electrophysiologic studies indicated that the mutant slowly activating voltage‐gated K+ channel (I_Ks) is dysfunctional. It showed reduced total activating and deactivating currents (P<0.01), with dramatically positive shift of voltage dependence of activation by ≈10 mV (P<0.05).

Conclusions

The current study uncovered concealed maternal type 1 long‐QT syndrome as a potential novel cause behind recurrent fetal loss.

Copy number variation characterization and possible candidate genes in miscarriage and stillbirth by next-generation sequencing analysis

Background

The present study aimed to explore the etiological relationship between miscarriage and stillbirth and copy number variations (CNVs), as well as provide useful genetic guidance for high‐risk pregnancy.

Methods

In total, 659 fetal samples were recruited and subjected to DNA extraction and CNV sequencing (CNV‐seq), relevant medical records were collected.

Results

There were 322 cases (48.86%) with chromosomal abnormalities, including 230 with numerical abnormalities and 92 with structural abnormalities. Chromosomal monosomy variations mainly occurred on sex chromosomes and trisomy variations mainly occurred on chromosomes 16, 22, 21, 18, 13 and 15. In total, 41 pathogenic CNVs (23 microdeletions and 18 microduplications) were detected in 27 fetal tissues. The rates of numerical chromosomal abnormalities were 29.30% (109/372), 32.39% (57/176) and 57.66% (64/111) in < 30‐year‐old, 30–34‐year‐old and ≥ 35‐year‐old age pregnant women, respectively, and increased with an increasing age (p < 0.001). There was statistically significant difference (χ² = 7.595, p = 0.022) in the rates of structural chromosomal abnormalities in these groups (13.71%, 18.75% and 7.21%, respectively). The rates of numerical chromosomal abnormalities were 45.44% (219/482), 7.80% (11/141) and 0% (0/36) in the ≤ 13 gestational weeks, 14–27 weeks and ≥ 28 weeks groups, respectively, and decreased with respect to the increasing gestational age of the fetuses (p < 0.001).

Conclusions

The present study has obtained useful and accurate genetic etiology information that will provide useful genetic guidance for high‐risk pregnancies.

Carrier frequency and incidence estimation of Smith-Lemli-Opitz syndrome in East Asian populations by Genome Aggregation Database (gnomAD) based analysis

Background

Smith–Lemli–Opitz syndrome (SLOS) is an autosomal, recessively inherited congenital malformation syndrome characterized by multiple congenital anomalies such as microcephaly with mental defects, distinctive facial features, genital abnormalities, and 2–3 syndactyly of the toes. SLOS is caused by defective 7-dehydrocholesterol reductase, which is encoded by the DHCR7 gene. This study aimed to analyze the carrier frequency and expected incidence of SLOS in East Asians and Koreans using exome data from the Genome Aggregation Database (gnomAD) through the 2015 American College of Medical Genetics and Genomics and the Association for Molecular Pathology guideline (2015 ACMG-AMP guideline).

Methods

We analyzed 9197 exomes for East Asian populations from gnomAD, comprising 1909 Korean, 76 Japanese, and 7212 other East Asian populations. All identified variants were classified according to the 2015 ACMG-AMP guideline.

Results

According to the 2015 ACMG-AMP guideline, 15 pathogenic variant/likely pathogenic variant (PV/LPV) cases were identified in 33 East Asian individuals (33/9191 = 0.4%). Among them, four PVs/LPVs were identified in 19 Korean individuals (19/1909 = 1.0%). The predicted incidence, based upon the carrier rates of PV/LPV of DHCR7 alleles, is 1 in 310,688 in East Asians and l in 40,380 in Koreans.

Conclusions

This study is the first to identify carrier frequencies in East Asians and Koreans using gnomAD. It was confirmed that East Asians (0.4%) had a lower carrier frequency than did other ethnicities (1–3%) and Koreans (1.0%) had similar or lower carrier frequencies than other ethnicities. The variant spectrums of DHCR7 in East Asian and Korean populations differed greatly from those of other ethnic groups.