Pregnancy complications following fertility treatment-disentangling the role of multiple gestation

Prediction of pregnancy-related complications in women undergoing assisted reproduction, using machine learning methods

OBJECTIVE

To use machine learning methods to develop prediction models of pregnancy complications in women who conceived with assisted reproductive techniques (ART).

DESIGN

A nation-wide register-based cohort study with prospectively collected data.

SETTING

Swedish national registers and nationwide quality IVF register.

PATIENT(S)

all nulliparous women who achieved birth within the first 3 ART treatment cycles between 2008 and 2016 in Sweden.

INTERVENTION(S)

Characteristics before the use of ART, such as demographics and medical history, were considered potential predictors in the development of before treatment prediction models. ART treatment details were further included in after treatment prediction models.

MAIN OUTCOME MEASURE(S)

Potential diagnoses of preeclampsia, placental complications (previa, accreta, and abruption), and postpartum hemorrhage were identified using the International Classification of Diseases recorded in the Swedish Medical Birth and Patient registers, respectively. Multiple prediction model algorithms were performed and compared for each outcome and treatment cycle, including logistic regression, decision tree model, naïve Bayes classification, support vector machine, random forest, and gradient boosting. The performance of each model was assessed with C statistic, and nested cross-validation was used to aid model selection and hyperparameter tuning.

RESULT(S)

A total of 14,732 women gave birth after the first (N = 7,302), second (N = 4,688), or third (N = 2,742) ART cycle, representing birth rates of 24.1%, 23.8%, and 22.0%. Overall prediction performance did not vary much across the different methods used. In the first cycle, the before treatment prediction performance was at best 66%, 66%, and 60% for preeclampsia, placental complications, and postpartum hemorrhage, respectively. Inclusion of after treatment characteristics conferred slight improvement (approximately 1%-5%), as did prediction in later cycles (approximately 1%-5%). The top influential and consistent predictors included age, region of residence, infertility diagnosis, and type of embryo transfer (fresh or frozen) in the later (2nd and 3rd) cycles. Body mass index was a top predictor of preeclampsia and was also influential for placental complications but not for postpartum hemorrhage.

CONCLUSION(S)

The combined use of demographics, medical history, and ART treatment information was not enough to confidently predict serious pregnancy complications in women who conceived with ART. Future studies are needed to assess if additional longitudinal follow-up during pregnancy can improve the prediction to allow clinical protocol development.

Risk-reducing salpingectomy with delayed oophorectomy to prevent ovarian cancer in women with an increased inherited risk: insights into an alternative strategy

Epithelial ovarian cancer (EOC) is the most lethal type of gynaecological cancer, due to lack of effective screening possibilities and because the disease tends to metastasize before onset of symptoms. Women with an increased inherited risk for EOC are advised to undergo a risk-reducing salpingo-oophorectomy (RRSO), which decreases their EOC risk by 96% when performed within guideline ages. However, it also induces premature menopause, which has harmful consequences. There is compelling evidence that the majority of EOCs originate in the fallopian tube. Therefore, a risk-reducing salpingectomy with delayed oophorectomy (RRS with DO) has gained interest as an alternative strategy. Previous studies have shown that this alternative strategy has a positive effect on menopause-related quality of life and sexual health when compared to the standard RRSO. It is hypothesized that the alternative strategy is non-inferior to the standard RRSO with respect to oncological safety (EOC incidence). Three prospective studies are currently including patients to compare the safety and/or quality of life of the two distinct strategies. In this article we discuss the background, opportunities, and challenges of the current and alternative strategy.

Accounting for Twins and Other Multiple Births in Perinatal Studies Conducted Using Healthcare Administration Data

The analysis of perinatal studies is complicated by twins and other multiple births even when they are not the exposure, outcome, or a confounder of interest. Common approaches to handling multiples in studies of infant outcomes include restriction to singletons, counting outcomes at the pregnancy-level (i.e., by counting if at least one twin experienced a binary outcome), or infant-level analysis including all infants and, typically, accounting for clustering of outcomes by using generalised estimating equations or mixed effects models. Several healthcare administration databases only support restriction to singletons or pregnancy-level approaches. For example, in MarketScan insurance claims data, diagnoses in twins are often assigned to a single infant identifier, thereby preventing ascertainment of infant-level outcomes among multiples. Different approaches correspond to different causal questions, produce different estimands, and often rely on different assumptions. We demonstrate the differences that can arise from these different approaches using Monte Carlo simulations, algebraic formulas, and an applied example. Furthermore, we provide guidance on the handling of multiples in perinatal studies when using healthcare administration data.

Body Mass Index, Adverse Pregnancy Outcomes, and Cardiovascular Disease Risk

BACKGROUND

Obesity is a well-established risk factor for both adverse pregnancy outcomes (APOs) and cardiovascular disease (CVD). However, it is not known whether APOs are mediators or markers of the obesity-CVD relationship. This study examined the association between body mass index, APOs, and postpartum CVD risk factors.

METHODS

The sample included adults from the nuMoM2b (Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-To-Be) Heart Health Study who were enrolled in their first trimester (6 weeks-13 weeks 6 days gestation) from 8 United States sites. Participants had a follow-up visit at 3.7 years postpartum. APOs, which included hypertensive disorders of pregnancy, preterm birth, small-for-gestational-age birth, and gestational diabetes, were centrally adjudicated. Mediation analyses estimated the association between early pregnancy body mass index and postpartum CVD risk factors (hypertension, hyperlipidemia, and diabetes) and the proportion mediated by each APO adjusted for demographics and baseline health behaviors, psychosocial stressors, and CVD risk factor levels.

RESULTS

Among 4216 participants enrolled, mean±SD maternal age was 27±6 years. Early pregnancy prevalence of overweight was 25%, and obesity was 22%. Hypertensive disorders of pregnancy occurred in 15%, preterm birth in 8%, small-for-gestational-age birth in 11%, and gestational diabetes in 4%. Early pregnancy obesity, compared with normal body mass index, was associated with significantly higher incidence of postpartum hypertension (adjusted odds ratio, 1.14 [95% CI, 1.10-1.18]), hyperlipidemia (1.11 [95% CI, 1.08-1.14]), and diabetes (1.03 [95% CI, 1.01-1.04]) even after adjustment for baseline CVD risk factor levels. APOs were associated with higher incidence of postpartum hypertension (1.97 [95% CI, 1.61-2.40]) and hyperlipidemia (1.31 [95% CI, 1.03-1.67]). Hypertensive disorders of pregnancy mediated a small proportion of the association between obesity and incident hypertension (13% [11%-15%]) and did not mediate associations with incident hyperlipidemia or diabetes. There was no significant mediation by preterm birth or small-for-gestational-age birth.

CONCLUSIONS

There was heterogeneity across APO subtypes in their association with postpartum CVD risk factors and mediation of the association between early pregnancy obesity and postpartum CVD risk factors. However, only a small or nonsignificant proportion of the association between obesity and CVD risk factors was mediated by any of the APOs, suggesting APOs are a marker of prepregnancy CVD risk and not a predominant cause of postpartum CVD risk.

Pregnancy by Oocyte Donation: Reviewing Fetal-Maternal Risks and Complications

Oocyte donation (OD) has greatly improved over the last three decades, becoming a preferred practice of assisted reproductive technology (ART) for infertile women wishing for motherhood. Through OD, indeed, it has become possible to overcome the physiological limitation due to the ovarian reserve (OR) exhaustion as well as the poor gamete reliability which parallels the increasing age of women. However, despite the great scientific contribution related to the success of OD in the field of infertility, this practice seems to be associated with a higher rate of major risky events during pregnancy as recurrent miscarriage, infections and placental diseases including gestational hypertension, pre-eclampsia and post-partum hemorrhage, as well as several maternal-fetal complications due to gametes manipulation and immune system interaction. Here, we will revisit this questioned topic since a number of studies in the medical literature focus on the successful aspects of the OD procedure in terms of pregnancy rate without, however, neglecting the risks and complications potentially linked to external manipulation or heterologous implantation.

Association of chorioamnionitis with infertility treatment and subsequent neonatal outcomes in the US: a population-based cohort study

BACKGROUND

Chorioamnionitis (CAM) is a common risk factor for preterm births, resulting in several adverse outcomes. The association between infertility treatment and CAM is unclear. Therefore, this study examined the association between infertility treatment and CAM and described subsequent neonatal outcomes.

METHODS

This population-based cohort study used data from the National Vital Statistics System Database. We included women who had a singleton live birth from January 1, 2016 to December 31, 2018. Women-infant pairs were stratified by infertility treatment, and the main outcome was a reported diagnosis of CAM in a checkbox format: clinical CAM or maternal temperature of > 38 °C. Multivariate logistic regression was used to examine the association between infertility treatment and CAM and the effect of infertility treatment on neonatal outcomes in women diagnosed with CAM.

RESULTS

The final sample comprised 10,900,495 woman-infant pairs, and 1.4% received infertility treatment. Compared with the natural conception group, women receiving infertility treatment had a significantly higher risk of CAM (adjusted odds ratio [aOR] 1.772 [95% confidence interval {CI}, 1.718-1.827]). Furthermore, newborns exposed to CAM had a higher risk of very low birth weight (VLBW) (aOR, 2.083 [95% CI, 1.664-2.606], P < .001), preterm birth (aOR, 1.497 [95% CI, 1.324-1.693]; P < .001), neonatal intensive care unit admission (aOR, 1.234 [95% CI, 1.156-1.317]; P < .001), and other adverse neonatal outcomes in the infertility treatment group compared with ones conceived naturally.

CONCLUSIONS

This study found that women who received infertility treatment had a higher risk of CAM. And CAM deteriorated neonatal outcomes in the infertility treatment group.

Risk of stillbirth and neonatal death in singletons born after fresh and frozen embryo transfer: cohort study from the Committee of Nordic Assisted Reproduction Technology and Safety

OBJECTIVES

To investigate whether risks of stillbirth and neonatal death differ after fresh embryo transfers (fresh-ETs) and frozen embryo transfers (frozen-ETs) compared with singletons conceived without medical assistance.

DESIGN

A population-based cohort study.

SETTING

Not applicable.

PATIENT(S)

Data linkage between the nationwide Medical Birth Registries in Denmark (1994-2014), Norway and Sweden (1988-2015), and national quality registries and databases on assisted reproductive technology identified a total of 4,590,853 singletons, including 78,642 conceived by fresh-ET and 18,084 by frozen-ET.

INTERVENTION(S)

None MAIN OUTCOME MEASURE(S): Stillbirth (fetal death before and during delivery) and neonatal death (live born with death 0-27 days postpartum).

RESULT(S)

Overall, 17,123 (0.37%) singletons were stillborn and 7,685 (0.17%) died neonatally. Compared with singletons conceived without medical assistance, the odds of stillbirth were similar after fresh-ET and frozen-ET, whereas the odds of neonatal death were high after fresh-ET (odds ratio [OR], 1.69; 95% confidence interval [CI], 1.46-1.95) and frozen-ET (OR, 1.51; 95% CI, 1.08-2.10). Preterm birth (<37 gestational weeks) was more common after fresh-ET (8.0%) and frozen-ET (6.6%) compared with singletons conceived without medical assistance (5.0%), and strongly associated with neonatal mortality across all conception methods. Within gestational age categories, risk of stillbirth and neonatal death was similar for all conception methods, except that singletons from fresh-ET had a higher risk of stillbirth during gestational week 22-27 (OR, 1.85; 95% CI, 1.51-2.26).

CONCLUSION(S)

Overall, the risk of stillbirth was similar after fresh-ET and frozen-ET compared with singletons conceived without medical assistance, whereas neonatal mortality was high, possibly mediated by the high risk of preterm birth when compared with singletons conceived without medical assistance. Our results gave no clear support for choosing one treatment over the other.

Risk of Hypertensive Disorders in Pregnancy After Fresh and Frozen Embryo Transfer in Assisted Reproduction: A Population-Based Cohort Study With Within-Sibship Analysis

BACKGROUND

Frozen embryo transfer (frozen-ET) is increasingly common because of improved cryopreservation methods and elective freezing of all embryos. Frozen-ET is associated with higher risk of hypertensive disorders in pregnancy than both natural conception and fresh embryo transfer (fresh-ET), but whether this is attributable to parental factors or treatment is unknown.

METHODS

Using the Medical Birth Registries of Denmark (1994-2014), Norway, and Sweden (1988-2015), linked to data from national quality registries and databases on assisted reproduction, we designed a population-based cohort study with within-sibship comparison. We included 4 426 691 naturally conceived, 78 300 fresh-ET, and 18 037 frozen-ET singleton pregnancies, of which 33 209 sibships were conceived using different conception methods. Adjusted odds ratios (aOR) of hypertensive disorders in pregnancy for fresh-ET and frozen-ET versus natural conception with 95% CI were estimated using multilevel logistic regression, where random effects provided conventional population-level estimates and fixed effects gave within-sibship estimates. Main models included adjustment for birth year, maternal age, parity, and country.

RESULTS

Risk of hypertensive disorders in pregnancy was higher after frozen-ET compared to natural conception, both at population-level (7.4% versus 4.3%, aOR, 1.74 [95% CI, 1.61-1.89]) and within sibships (aOR, 2.02 [95% CI, 1.72-2.39]). For fresh-ET, risk was similar to natural conception, both at population-level (aOR, 1.02 [95% CI, 0.98-1.07]) and within sibships (aOR, 0.99 [95% CI, 0.89-1.09]).

CONCLUSIONS

Frozen-ET was associated with substantially higher risk of hypertensive disorders in pregnancy, even after accounting for shared parental factors within sibships.

PGT pregnancies have a similar risk for post-partum complications as naturally conceived pregnancies

RESEARCH QUESTION

Do preimplantation genetic testing (PGT) pregnancies have higher post-partum complications compared with naturally conceived pregnancies?

DESIGN

Retrospective cohort study conducted in 2008-2020 at the Shaare Zedek Medical Center (SZMC), including all patients aged 18-45 years old who conceived following PGT with a singleton live birth >24 weeks. Data were collected from computerized hospital databases and patient files. There were two control groups: (i) pregnancies following IVF-ICSI (intracytoplasmic sperm injection); (ii) four neighbourhood controls for each case delivery (two women delivered before and two after) of women with naturally conceived pregnancies.

RESULTS

Overall, 120 PGT, 779 IVF-ICSI and 3507 naturally conceived deliveries were included. Demographic variables were similar apart from slightly higher age in the PGT (P = 0.003) and ICSI (P = 0.002) groups (31.07 ± 4.38 PGT, 31.66 ± 5.03 ICSI, 28.77 ± 5.72 naturally conceived). Composite post-partum placental-related complications (manual lysis of placenta, revision of uterine cavity, haemoglobin drop ≥3 g/dl, post-partum haemorrhage, need for blood transfusion) were more prevalent in both the PGT and IVF-ICSI groups as opposed to naturally conceived (20.0% versus 18.9% versus 10.3%, respectively, P < 0.001, P = 0.007). In a multivariate regression model PGT was not found to be independently associated with composite post-partum placental-related complications (adjusted odds ratio [aOR] 1.44, 95% confidence interval [CI] 0.83-2.15), while IVF-ICSI pregnancies had increased risk (aOR 1.52, 95% CI 1.20-1.97) compared with natural conception. No difference was found between fresh and frozen cycles or between day 3 and day 5 embryo transfer.

CONCLUSIONS

PGT pregnancies have a comparable risk of post-partum placental-related complications to naturally conceived pregnancies, unlike IVF-ICSI pregnancies. It is possible that infertility itself is the main mediator for post-partum complications in IVF-ICSI pregnancies.

Identification of risk factors for incident cervical insufficiency in nulliparous and parous women: a population-based case-control study

BACKGROUND

Cervical insufficiency is one of the underlying causes of late miscarriage and preterm birth. Although many risk factors have been identified, the relative magnitude of their association with risk in nulliparous versus parous women has not been well demonstrated, especially for incident cervical insufficiency (ICI). The aim of this study was to investigate and compare the magnitude of the association of ICI with predictive factors in nulliparous and parous women, and to further investigate various aspects of obstetric history for parous women.

METHODS

Pregnant women with a first diagnosis of cervical insufficiency were compared to a random sample of control pregnancies from women with no diagnosis by using Swedish national health registers. Demographic, reproductive, and pregnancy-specific factors were compared in case and control pregnancies, and relative risks presented as odds ratios (OR), stratified by nulliparous/parous. Independent associations with ICI were estimated from multivariable logistic regression. Associations with obstetric history were further estimated for multiparous women.

RESULTS

A total of 759 nulliparous ICI cases and 1498 parous cases were identified during the study period. Multifetal gestation had a strong positive association with ICI in both groups, but of much larger magnitude for nulliparous women. The number of previous miscarriages was also a much stronger predictor of risk in nulliparous women, especially for multifetal pregnancies. History of preterm delivery (<37 weeks' gestation) was an independent predictor for parous women, and for those whose most recent delivery was preterm, the association with ICI increased with each additional week of prematurity. A previous delivery with prolonged second stage of labor or delivery of a very large infant were both inversely associated with risk of ICI in the current pregnancy.

CONCLUSIONS

The differences in importance of predictive risk factors for incident cervical insufficiency in nulliparous and parous women can help resolve some of the inconsistencies in the literature to date regarding factors that are useful for risk prediction. Stratifying on parity can inform more targeted surveillance of at-risk pregnancies, enable the two groups of women to be better informed of their risks, and eventually inform screening and intervention efforts.

The Maternal-Neonatal Outcomes of Twin Pregnancies with Preeclampsia and Their Association with Assisted Reproductive Technology: A Retrospective Study

Objective: This study aimed to investigate the maternal−neonatal outcomes of twin pregnancies of mothers with preeclampsia and their association with assisted reproductive technology (ART). Methods: A retrospective study on the clinical and maternal−neonatal outcome data of 698 women with twin pregnancies who delivered in our hospital from December 2013 to September 2021 was conducted. Continuous variables were analyzed using a Student’s t-test or Wilcoxon rank-sum test. Categorical variables were analyzed using the Chi-square test. The risk factors of twin pregnancies with preeclampsia were analyzed by logistic regression. Results: The rate of twin pregnancy complicated by preeclampsia was 17.62% (123/698). Logistic regression analysis showed that ART increased the risk of preeclampsia in twin pregnancies (AOR: 1.868, 95% CI: 1.187−2.941). Mothers with preeclampsia carrying twins conceived with ART had a higher rate of delivery at gestational week < 34 (29.9% vs. 12.5%) and asphyxia of the neonate at 5 min after delivery (13.4% vs. 1.8%) than those with preeclampsia conceived without ART (p < 0.05). Conclusions: ART increases the risk of preeclampsia in twin pregnancies and the rate of adverse maternal−neonatal outcomes for twin pregnancies with preeclampsia. The policy of single embryo transfer is a method to reduce the adverse pregnancy outcomes of ART.

Multifoetal gestations mediate the effect of in vitro fertilisation (IVF) on ischaemic placental disease in autologous oocyte IVF more than donor oocyte IVF

BACKGROUND

Ischaemic placental disease (IPD) affects 16%-23% of pregnancies in the United States. In vitro fertilisation (IVF) is a risk factor for IPD, and the magnitude of increase in risk differs for individuals using donor oocytes (donor IVF) versus their own oocytes (autologous IVF). In addition, multifoetal gestations, which are more common in IVF than non-IVF pregnancies, also are a risk factor for IPD.

OBJECTIVE

To quantify the contribution of multifoetal gestations to the association between IVF and IPD.

METHODS

We conducted a retrospective cohort study at a tertiary hospital from 1 January, 2000 to 1 August 2018 using electronic medical records and state vital statistics data. IPD was defined as preeclampsia, placental abruption, small for gestational age (SGA) birth or an intrauterine foetal demise due to placental insufficiency. We used mediation analysis to decompose the total effect of IVF on IPD into a natural direct effect and an indirect effect through multifoetal gestations. We repeated the analyses separately for donor and autologous IVF. All models were adjusted for maternal age, race, parity, insurance, year of delivery and account for multiple pregnancies per person.

RESULTS

We identified 86,514 deliveries, of which 281 resulted from donor IVF and 4173 resulted from autologous IVF. IVF pregnancies had 1.99 (95% CI 1.88, 2.10) times the risk of IPD compared to non-IVF pregnancies, and 75.5% of this increased risk was mediated by multifoetal gestations. Autologous IVF pregnancies had 1.95 (95% CI 1.84, 2.07) times the risk of IPD compared to non-IVF pregnancies, and the per cent mediated was 78.8%. Donor IVF pregnancies had 2.50 (95% CI 2.09, 2.92) times the risk of IPD, but the per cent mediated was 37.5%.

CONCLUSION

The majority of the association between autologous IVF and IPD was mediated through multifoetal gestations; however, this was not the case for donor IVF pregnancies.

Parametric-Regression-Based Causal Mediation Analysis of Binary Outcomes and Binary Mediators: Moving Beyond the Rareness or Commonness of the Outcome

In the causal mediation framework, several parametric-regression–based approaches have been introduced in the last decade for estimating natural direct and indirect effects. For a binary outcome, a number of proposed estimators use a logistic model and rely on specific assumptions or approximations that may be delicate or not easy to verify in practice. To circumvent the challenges prompted by the rare outcome assumption in this context, an exact closed-form natural-effects estimator on the odds ratio scale was recently introduced for a binary mediator. In this work, we further push this exact approach and extend it for the estimation of natural effects on the risk ratio and risk difference scales. Explicit formulas for the delta method standard errors are provided. The performance of our proposed exact estimators is demonstrated in simulation scenarios featuring various levels of outcome rareness/commonness. The total effect decomposition property on the multiplicative scales is also examined. Using a SAS macro (SAS Institute, Inc., Cary, North Carolina) we developed, our approach is illustrated to assess the separate effects of exposure to inhaled corticosteroids and placental abruption on low birth weight mediated by prematurity. Our exact natural-effects estimators are found to work properly in both simulations and the real data example.

Women with multiple gestations have an increased risk of development of hypertension in the future

Background

Multiple gestations are associated with an increased incidence of preeclampsia. However, there exists no evidence for an association between multiple gestations and development of hypertension(HTN) later in life. This study aimed to determine whether multiple gestations are associated with HTN beyond the peripartum period.

Methods

In this retrospective nationwide population-based study, women who delivered a baby between January 1, 2007, and December 31, 2008, and underwent a national health screening examination within one year prior to their pregnancy were included. Subsequently, we tracked the occurrence of HTN during follow-up until December 31, 2015, using International Classification of Diseases-10th Revision codes.

Results

Among 362,821 women who gave birth during the study period, 4,944 (1.36%) women had multiple gestations. The cumulative incidence of HTN was higher in multiple gestations group compared with singleton group (5.95% vs. 3.78%, p < 0.01, respectively). On the Cox proportional hazards models, the risk of HTN was increased in women with multiple gestations (HR 1.35, 95% CI 1.19, 1.54) compared with those with singleton after adjustment for age, primiparity, preeclampsia, atrial fibrillation, body mass index, blood pressure, diabetes mellitus, high total cholesterol, abnormal liver function test, regular exercise, and smoking status.

Conclusions

Multiple gestations are associated with an increased risk of HTN later in life. Therefore, guidelines for the management of high-risk patients after delivery should be established.

Assisted Reproductive Techniques, ADHD, and School Performance

OBJECTIVES

To examine the long-term impact of assisted reproductive techniques (ART) on offspring neurodevelopment, accounting for parental factors and the role of infertility.

METHODS

Linkage of national registers allowed follow-up of >2.4 million children born in Sweden 1986-2012. Information on ART was retrieved from fertility clinics, medical records, and maternal self-report. Attention-deficit/hyperactivity disorder (ADHD) was identified from specialist diagnosis and/or use of medication through 2018. School performance was assessed from records of ninth year final grade averages (0-20) and eligibility for upper secondary school through 2017.

RESULTS

Children conceived with ART had lower risk of ADHD (hazard ratio 0.83; 95% confidence interval [CI]: 0.80 to 0.87) and did better in school (grade mean difference 1.15; 95% CI: 1.09 to 1.21 and eligibility odds ratio 1.53; 95% CI: 1.45 to 1.63) compared with all other children. Differences in parental characteristics explained and even reversed associations, whereas no disadvantage was seen when the comparison was restricted to children of couples with known infertility (adjusted hazard ratio 0.95; 95% CI: 0.90 to 1.00, adjusted mean difference 0.05; 95% CI: -0.01 to 0.11, and adjusted odds ratio 1.03; 95% CI: 0.96 to 1.10). Among children conceived with ART, there was furthermore no indication that intracytoplasmic sperm injection (compared with standard in vitro fertilization) or frozen (compared with fresh) embryo transfer had any adverse influence.

CONCLUSIONS

With this nationwide, long-term follow-up, we provide additional reassurance concerning offspring neurodevelopment after use of ART, finding no indication for concern about risk of ADHD or school performance in adolescence.

Preterm delivery risk in infertile women who conceived after reproductive surgery: natural conception versus IVF/ICSI

STUDY QUESTION

Is preterm delivery an infertility treatment-related adverse outcome in infertile women who conceived after reproductive surgery?

SUMMARY ANSWER

Compared with matched fertile women, preterm delivery appears to be a modest infertility treatment-related adverse outcome in infertile women who have reproductive surgery then conceived naturally or after IVF/ICSI.

WHAT IS KNOWN ALREADY

Most observational studies have shown that women who receive any infertility treatment are more likely to deliver preterm than do fertile women. However, studies on the outcome of pregnancies in infertile women who conceive naturally after reproductive surgery are scarce.

STUDY DESIGN, SIZE, DURATION

This was a single-centre historical two-part study: cohort and matched cohort study. Anonymized data of 761 infertile women who conceived after reproductive surgery and 758 fertile women were obtained by linking three computerized databases from 1 July 2012 to 31 December 2015.

PARTICIPANTS/MATERIALS, SETTING, METHODS

In the cohort study, we evaluated the association between the mode of conception and preterm delivery <37 and <32 gestational weeks in 703 infertile women, with a singleton pregnancy who conceived after reproductive surgery, using logistic regression adjusted for relevant co-variates to calculate the adjusted odds ratio with a 95% CI. In the matched cohort study, we evaluated preterm delivery as infertility treatment-related adverse outcome using the propensity score (PS) method. The matched cohort comprised 758 infertile women and 758 fertile women with a twin or singleton pregnancy. Infertile women conceived after reproductive surgery either naturally or through IVF/ICSI. Infertile and fertile women were matched using PS matching. Infertile and fertile women were matched for pre-defined risk factors for preterm delivery. Three infertile women out of an original 761 were not included in the analysis because they lacked all required matching variables. We performed a 1:1 matching with an optimal matching algorithm with a caliper width of the linear predictor of 0.1 standard deviations. The effect of reproductive surgery on preterm delivery was evaluated in the PS-matched sample using Pearson's χ2 test and presented as the odds ratio (OR) with 95% CI. All women delivered at the Department of Perinatology, University Medical Centre Ljubljana, Slovenia.

MAIN RESULTS AND THE ROLE OF CHANCE

Among 761 infertile women who conceived after reproductive surgery, 428 (56.2%) women conceived naturally and 333 (43.8%) conceived after IVF/ICSI. The incidence of twin pregnancies was significantly lower after natural conception (2.6% vs 14.1%). Among the 703 infertile women with a singleton pregnancy, 417 (59.3%) conceived naturally and 286 (40.7%) conceived after IVF/ICSI. Adjusted for maternal age and parity in infertile women with singleton pregnancies, IVF/ICSI showed a moderate association with preterm delivery <32 weeks. Compared with natural conception after reproductive surgery, the odds for preterm delivery after IVF/ICSI was 1.07 (95% CI 0.63-1.81) <37 weeks and 2.25 (95% CI 0.80-6.34) <32 weeks. Preterm delivery appears to be a modest infertility treatment-related adverse outcome. Compared with fertile women in the PS-matched sample, infertile women who conceived after reproductive surgery either naturally or after IVF/ICSI the odds of preterm delivery <37 weeks were 1.31 (95% CI 0.97-1.78) and odds of preterm delivery <32 weeks were 1.57 (95% CI 0.78-3.18). However, none of the estimations were statistically significant.

LIMITATIONS, REASONS FOR CAUTION

The main limitations of the study were the retrospective design, the heterogeneity of the types of reproductive surgery performed and underlying reproductive pathologies. The low number of preterm deliveries in the present study might influence the precision of estimations.

WIDER IMPLICATIONS OF THE FINDINGS

The present study aims to alter the prevailing opinion that reproductive surgery should only be considered preceding IVF to increase implantation and pregnancy rates after IVF. It implies that in selected infertile women who have had reproductive surgery, a high rate of natural conception, a low rate of multiple pregnancies, and a modest infertility treatment-related effect on preterm delivery should be the reasons to encourage natural conception after reproductive surgery. Furthermore, by allowing for natural conception, we can avoid a high-cost invasive medical procedure.

STUDY FUNDING/COMPETING INTEREST(S)

The study received no funding. We have no competing interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Superovulation with gonadotropin-releasing hormone agonist or chorionic gonadotropin for ovulation trigger differentially affects leukocyte populations in the peri-implantation mouse uterus

OBJECTIVE

To investigate the effect of superovulation with human chorionic gonadotropin (hCG) or gonadotropin-releasing hormone agonist (GnRHa) trigger on leukocyte density and expression of leukocyte-specific genes in the peri-implantation period in the mouse uterus.

DESIGN

Laboratory research.

SETTING

University laboratory facility.

INTERVENTIONS

Female mice were mated to fertile male mice in one of three protocols: (1) natural mating or mating following injection with pregnant mare serum gonadotropin followed by trigger with (2) GnRHa or (3) hCG. Female mice were killed prior to implantation, 3 days after ovulation (E3.5), and the ovaries and uterine tissue were collected. Total RNA was isolated and assayed using quantitative reverse transcription polymerase chain reaction, and the uterine tissue was stained for histologic analysis of immune cell markers.

MAIN OUTCOME MEASURES

Endometrial leukocyte (CD45) and vessel density (CD31) by immunohistochemical staining; expression of leukocyte markers CD11b, CD335, and CD22, by quantitative reverse transcription polymerase chain reaction in the whole uterine tissue.

RESULTS

Superovulation decreased (compared with controls) the endometrial leukocyte density, based on the number of cells staining for CD45, and endometrial vessel density, based on the number of cells staining for CD31. Leukocyte density was additionally decreased in the GnRHa trigger group compared with that in the hCG trigger group. Superovulation with hCG and GnRHa triggers decreased the uterine expression of the B-cell marker CD22 compared with controls. The expression of the natural killer cell marker CD11b was decreased by the hCG trigger but not by the GnRHa. Abundance of mRNA encoding the CD335 natural killer cell marker was not affected by superovulation or trigger agent.

CONCLUSIONS

In mice, superovulation with the GnRHa trigger compared with that with the hCG trigger differentially alters key immunologic factors in the uterine peri-implantation. These altered immunologic factors have roles in angiogenesis that may assist in elucidating the effects of assisted reproductive technologies on implantation efficiency and fetal growth and development.

The importance of mediation in reproductive health studies

A mediator is a factor that occurs after the exposure of interest, precedes the outcome of interest (i.e. between the exposure and the outcome) and is associated with both the exposure and the outcome of interest (i.e. is on the pathway between exposure and outcome). Mediation analyses can be valuable in many reproductive health contexts, as mediation analysis can help researchers to better identify, quantify and understand the underlying pathways of the association they are studying. The purpose of this commentary is to introduce the concept of mediation and provide examples that solidify understanding of mediation for valid discovery and interpretation in the field of reproductive medicine.

Pregnancy outcomes of Chinese women undergoing IVF with embryonic cryopreservation as compared to natural conception

Background

To examine differences in the maternal characteristics and pregnancy outcomes of Chinese women with various causes of infertility who underwent in vitro fertilization (IVF) with embryonic cryopreservation treatment.

Methods

Cases were pregnancies after IVF-ET with embryonic cryopreservation; controls were spontaneously conceived pregnancies. Subgroup analysis was carried out according to etiology of infertility. The IVF treatment group was divided into 5 subgroups according to infertility etiology as follows: ovulation disorder, tubal disease, male infertility, endometriosis, and mixed infertility. Data on demographic characteristics, medical history, laboratory tests, and delivery were reviewed. Logistic regression analysis was performed for pregnancy and perinatal complications and neonatal outcomes. The multivariable model was adjusted for potential confounders.

Results

Among singleton pregnancies, compared with spontaneous pregnancies, IVF pregnancies were associated with significant increases in the rates of the following: gestational diabetes mellitus (GDM) (aOR 1.76[95% CI 1.33–2.33]), preeclampsia (2.60[1.61–4.20]), preterm preeclampsia (4.52[2.03–10.06]), postpartum hemorrhage (1.57[1.04–2.36]), intrahepatic cholestasis of pregnancy (3.84[1.06–13.94]), preterm premature rupture of membranes (2.11[1.17–3.81]), preterm birth (1.95[CI 1.26–3.01]), low birthweight (1.90[1.13–3.20]), macrosomia (1.53[1.03–2.27]), and neonatal intensive care unit (NICU) admission (1.69[1.22–2.34]) in the ovulation disorder group; GDM (1.50[1.21–1.86]), placenta previa (2.70[1.59–4.59]), placenta accreta (1.78[1.10–2.89]), postpartum hemorrhage (1.61[1.19–2.18]), macrosomia (1.60[1.21–2.13]) and 5-min Apgar score ≤ 7 (4.09[1.04–16.08]) in the tubal disease group; placenta previa (9.33[4.22–20.62]), small for gestational age (2.29[1.04–5.08]), macrosomia (2.00[1.02–3.95]) and NICU admission (2.35[1.35–4.09]) in the endometriosis group; placenta previa (4.14[2.23–7.68]) and placenta accreta (2.05[1.08–3.87]) in the male infertility group; and GDM (1.85[1.15–2.98]), placenta previa (4.73[1.83–12.21]), placental abruption (3.39[1.20–9.56]), chorioamnionitis (2.93[1.04–8.26]), preterm birth (2.69[1.41–5.15]), and 1-min Apgar score ≤ 7 (4.68[1.62–13.51]) in the mixed infertility group. Among multiple pregnancies, most of the differences that were significant in singleton pregnancies were less extensive or had disappeared.

Conclusions

Infertility etiology within the IVF population was found to affect maternal and neonatal outcomes among all births. During the perinatal period, infertility etiology appears to be an additional risk factor for abnormal pregnancy outcomes besides the use of IVF techniques compared with spontaneous pregnancies. Higher risk was found for ovulation disorders, and lower risk was found for male infertility.

Mediational E-values: Approximate Sensitivity Analysis for Unmeasured Mediator-Outcome Confounding

BACKGROUND

Mediation analysis is a powerful tool for understanding mechanisms, but conclusions about direct and indirect effects will be invalid if there is unmeasured confounding of the mediator-outcome relationship. Sensitivity analysis methods allow researchers to assess the extent of this bias but are not always used. One particularly straightforward technique that requires minimal assumptions is nonetheless difficult to interpret, and so would benefit from a more intuitive parameterization.

METHODS

We conducted an exhaustive numerical search over simulated mediation effects, calculating the proportion of scenarios in which a bound for unmeasured mediator-outcome confounding held under an alternative parameterization.

RESULTS

In over 99% of cases, the bound for the bias held when we described the strength of confounding directly via the confounder-mediator relationship instead of via the conditional exposure-confounder relationship.

CONCLUSIONS

Researchers can conduct sensitivity analysis using a method that describes the strength of the confounder-outcome relationship and the approximate strength of the confounder-mediator relationship that, together, would be required to explain away a direct or indirect effect.

Association between in vitro fertilization and ischemic placental disease by gestational age

OBJECTIVE

To evaluate the association between in vitro fertilization (IVF) and ischemic placental disease (IPD), stratified by gestational age.

DESIGN

We performed a secondary analysis of a retrospective cohort study of deliveries.

SETTING

Deliveries were performed over 15 years at a single tertiary hospital.

PATIENT(S)

We included all parturients who had a live born infant or an intrauterine fetal demise (IUFD).

INTERVENTION(S)

We compared pregnancies resulting from IVF cycles to non-IVF pregnancies.

MAIN OUTCOME MEASURE(S)

The primary outcomes were preterm and term IPD (preeclampsia, placental abruption, small-for-gestational age infant [SGA], or an intrauterine fetal demise [IUFD] due to placental insufficiency).

RESULT(S)

Of the 69,084 deliveries during the study period, 3,763 (5.4%) were conceived with IVF. The incidence of preterm delivery was 32.6% in IVF pregnancies and 10.8% in non-IVF pregnancies. Multiple gestations were more common in IVF pregnancies. Compared to non-IVF pregnancies, IVF pregnancies were more likely to develop both preterm and term IPD, even after adjustment for maternal age and parity. The risk of preterm IPD was 4 times higher (95% confidence interval, 3.7-4.4) in patients who underwent IVF compared with those who did not undergo IVF. Among parturients who delivered at ≥37 weeks of gestation, IVF pregnancies had 1.7 times the risk of term IPD (95% confidence interval, 1.6-1.9) compared with non-IVF pregnancies.

CONCLUSION(S)

IVF was strongly associated with preterm IPD. We found a similar, but attenuated, association between IVF and term IPD. The stronger association with preterm IPD suggests an association between IVF and placental insufficiency.

Associations of Assisted Reproductive Technology and Twin Pregnancy With Risk of Congenital Heart Defects

IMPORTANCE

The extent to which assisted reproductive technology is associated with increased risk of congenital heart defects independent of its known association with twinning remains uncertain.

OBJECTIVE

To assess the extent to which assisted pregnancy is associated with increased risk of congenital heart defects independent of its known association with twinning.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective cohort study linked records of congenital heart defect diagnoses with assisted reproductive technology cycles in 507 390 singleton or twin pregnancies (10 149 assisted pregnancies and 497 241 nonassisted pregnancies), including singleton and twin early pregnancy losses, stillbirths, and live births (follow-up to 1 year of age) in Ontario, Canada, between April 1, 2012, and October 31, 2015. Statistical analysis was performed from January 1, 2017, to September 9, 2019.

EXPOSURES

Assisted reproductive technology and its 2 subtypes: intracytoplasmic sperm injection and in vitro fertilization without intracytoplasmic sperm injection.

MAIN OUTCOMES AND MEASURES

The main outcome was congenital heart defects (prevalence and relative risk measured as odds ratios [ORs]). Mediation analysis was performed to assess the extent to which the association between assisted reproductive technology and congenital heart defects was mediated by twinning.

RESULTS

Of 507 390 mother-infant pairs with singleton or twin pregnancies evaluated, the prevalence of congenital heart defects in assisted pregnancies (223 [2.2%]) was higher than that in nonassisted pregnancies (6057 [1.2%]; crude OR, 1.82; 95% CI, 1.59-2.09). The strength of the association between assisted pregnancy and congenital heart defects decreased after adjusting for several risk factors simultaneously (adjusted OR, 1.70; 95% CI, 1.48-1.95). Further mediation analysis indicated that most of the association between assisted pregnancy and congenital heart defects was mediated by twinning (adjusted OR, 1.68; 95% CI, 1.44-1.92), and the natural direct association of assisted pregnancy with congenital heart defects among singleton pregnancies was 1.09 (95% CI, 0.93-1.25). Mediation of twinning accounted for 87.3% of the association.

CONCLUSIONS AND RELEVANCE

Our study results suggest that the association between assisted reproductive technology and congenital heart defects may be mediated by twinning.

Association between uterine contractions before elective caesarean section and transient tachypnoea of the newborn: a retrospective cohort study

OBJECTIVE

We evaluated the association between the presence of predelivery uterine contractions and transient tachypnoea of the newborn (TTN) in women undergoing an elective caesarean section.

DESIGN

A retrospective cohort study.

SETTING

National Hospital Organization Kofu National Hospital, which is a community hospital, between January 2011 and May 2019.

PARTICIPANTS

The study included 464 women who underwent elective caesarean section. The exclusion criteria were missing data, twin pregnancy, neonatal asphyxia, general anaesthesia and elective caesarean section before term.

PRIMARY AND SECONDARY OUTCOME MEASURES

Patients were grouped according to the presence or absence of uterine contractions on a 40-min cardiotocogram (CTG) performed within 6 hours before caesarean delivery. We performed a multivariable logistic regression analysis to examine the association between predelivery uterine contractions and TTN.

RESULTS

The incidence of TTN was 9.9% (46/464), and 38.4% (178/464) of patients had no uterine contraction. The absence of uterine contractions was significantly associated with an increased risk of TTN (adjusted OR 2.04; 95% CI 1.09 to 3.82) after controlling for gestational diabetes mellitus, small for gestational age, male sex and caesarean section at 37 weeks.

CONCLUSIONS

Accurate risk stratification using a CTG could assist in the management of infants who are at risk of developing TTN.

Use of real-world evidence from healthcare utilization data to evaluate drug safety during pregnancy

PURPOSE

Because preapproval clinical trials typically exclude pregnant women, the evidence on drug safety during pregnancy required to inform drug labeling must come from postapproval controlled observational studies. Common designs have included pregnancy registries and case-control studies. Recently, pregnancy cohorts nested within healthcare utilization databases are increasingly being used. Despite clear advantages, these databases share some important limitations that may threaten the validity of studies emerging from them.

METHODS

This paper describes the distinctive methodological aspects of conducting drug safety studies in healthcare utilization databases with special emphasis on design and analytic approaches to minimize biases.

RESULTS

We describe considerations for study design, cohort definition, and follow-up. We then address issues related to exposure ascertainment based on prescription fills, including the importance of the etiologically relevant window and of properly accounting for preterm births. This is followed by a discussion of advantages and challenges when ascertaining maternal and infant outcomes based on secondary data. We then explore useful approaches to address confounding within the context of pregnancy research and of the potential for selection bias when restricting the cohort to live births. Finally, we consider issues related to external validity and statistical significance. The examples are mainly drawn from a pregnancy cohort nested in the Medicaid Analytic Extract.

CONCLUSIONS

The approaches presented provide guidance regarding the important methodological considerations that need to be attended to in order to generate valid, minimally biased risk when using large healthcare utilization databases for drug safety surveillance in pregnancy.