The problem of confounding in studies of the effect of maternal drug use on pregnancy outcome

Safety surveillance of respiratory syncytial virus (RSV) vaccine among pregnant individuals: a real-world pharmacovigilance study using the Vaccine Adverse Event Reporting System

OBJECTIVES

To describe the post-marketing safety profile of respiratory syncytial virus prefusion F (RSVpreF) vaccine among pregnant individuals.

DESIGN

This study analysed adverse event (AE) reports submitted to the U.S. Food and Drug Administration's Vaccine Adverse Event Reporting System (VAERS) database following RSVpreF immunisation from 1 September 2023 to 23 February 2024.

SETTING

VAERS, as a national spontaneous vaccine safety surveillance system, provides insights into the safety profile of the RSVpreF vaccine in a real-world setting.

PARTICIPANTS

Surveillance data included all AE reports submitted to VAERS in pregnant individuals following vaccination.

EXPOSURE

Receipt of RSVpreF vaccine among pregnant individuals in the USA.

PRIMARY AND SECONDARY OUTCOME MEASURES

Descriptive statistics were used to assess all AE reports with RSVpreF, including frequency, gestational age at vaccination, time to AE onset, reported outcomes and proportion of serious reports. Data mining techniques were employed to identify disproportionate reporting of RSVpreF-event pairs. Reports of preterm births were clinically reviewed.

RESULTS

VAERS received 77 reports pertaining to RSVpreF vaccination in pregnant individuals, with 42 (54.55%) classified as serious. The most frequently reported non-pregnancy-specific AEs were headache, injection site erythema and injection site pain. For pregnancy-specific AEs, preterm birth was the most frequently reported (12.8%), followed by AE terms such as preterm premature rupture of membranes and caesarean section (each at 3.3%), and cervical dilatation, haemorrhage during pregnancy and uterine contractions during pregnancy (each at 1.4%). Our disproportionality analysis indicated signals for various AEs, particularly preterm birth, indicating that reports of preterm birth in conjunction with RSVpreF vaccination were observed more frequently than statistically expected. Most of the reported preterm births were moderate to late, occurring between 32 and less than 37 weeks of gestation. The median time from immunisation to the onset of preterm birth was 3 days, with two-thirds of cases reported within a week of vaccination.

CONCLUSIONS

The AEs reported to VAERS among pregnant individuals vaccinated with RSVpreF largely aligned with the safety profile observed in prelicensure studies; however, this analysis also highlights the previously observed safety signal for preterm birth. Active surveillance studies focusing on maternal and perinatal outcomes are needed to further evaluate this signal and guide future clinical recommendations.

Outcomes of long-acting injectable antipsychotics use in pregnancy: A literature review

BACKGROUND

Women with a history of serious psychotic disorders are at increased risk of disease relapse during pregnancy. Long-acting injectable (LAI) antipsychotics have been widely used to improve adherence and prevent relapse in patients with various severe psychotic disorders, but there is a lack of high-quality data from previous research on the safety of LAI antipsychotics during pregnancy.

AIM

To summarize relevant data on maternal, pregnancy, neonatal, and developmental outcomes from published cases of LAI antipsychotic use in pregnancy.

METHODS

A literature search was performed through November 11, 2023, using three online databases: PubMed/MEDLINE, Scopus, and Web of Science. Case reports or case series that reported information about the outcomes of pregnancy in women who used LAI antipsychotics at any point in pregnancy, with available full texts, were included. Descriptive statistics, narrative summation, and tabulation of the extracted data were performed.

RESULTS

A total of 19 publications satisfied the inclusion criteria: 3 case series, 15 case reports, and 1 conference abstract. They reported the outcomes of LAI antipsychotic use in 74 women and 77 pregnancies. The use of second-generation LAI antipsychotics was reported in the majority (n = 47; 61.0%) of pregnancies. First-generation LAI antipsychotics were administered during 30 pregnancies (39.0%). Most of the women (approximately 64%) had either satisfactory control of symptoms or no information about relapse, while approximately 12% of them had developed gestational diabetes mellitus. A minority of cases reported adverse outcomes such as stillbirth, spontaneous abortion, preterm birth, low birth weight, congenital anomalies, and neurological manifestations in newborns. However, there were no reports of negative long-term developmental outcomes.

CONCLUSION

Currently available data seem reassuring, but further well-designed studies are required to properly evaluate the risks and benefits of LAI antipsychotic use during pregnancy.

Perinatal Outcomes of Twin Gestations with and without Gestational Diabetes Mellitus

OBJECTIVE

Existing data suggest that obstetric outcomes for individuals with twin gestations, who have gestational diabetes mellitus (GDM), may be comparable to those who do not have GDM, yet studies are limited by small sample sizes. The aim of this study was to examine differences in maternal and neonatal outcomes of individuals with twin gestations based on presence of GDM.

METHODS

This was a population-based retrospective cohort study of individuals giving birth to twins in the United States between 2012 and 2014. Inclusion criteria were live births (≥24 weeks) and available information on GDM status; individuals with pregestational diabetes were excluded. Participants were categorized as either having had or not had GDM. Multivariable logistic regression was utilized to assess the independent association of GDM with adverse maternal outcomes, whereas generalized estimating equation models were used to estimate associations with neonatal outcomes to account for clustering.

RESULTS

Of 173,196 individuals meeting inclusion criteria, 13,194 (7.6%) had GDM. Individuals with GDM were more likely to be older, identify as Hispanic or Asian race and ethnicity, married, college educated, privately insured, and obese than those without GDM. After adjusting for potential confounding variables, those with GDM were more likely to have hypertensive disorders (18.0 vs. 10.2%) and undergo cesarean delivery (51.2 vs. 47.3%). Neonates born to individuals with GDM were more likely to require mechanical ventilation for greater than 6 hours (6.5 vs. 5.6%) and experience neonatal intensive care unit (NICU) admission (41.1 vs. 36.2%), but were less likely to be low birth weight or have small for gestational age status (16.2 vs. 19.5%). Findings were confirmed in a sensitivity analysis of neonates born at 32 weeks of gestation or greater.

CONCLUSION

Odds of poor obstetric and neonatal outcomes are increased for individuals with twin gestations complicated by GDM.

KEY POINTS

· Individuals with GDM and twin gestation have higher odds of developing hypertensive disorders during pregnancy and of undergoing cesarean delivery.. · Neonates of such pregnancies are less likely to be low birth weight or small for gestational age.. · Neonates of pregnancies complicated by GDM and twin gestation are more likely to require mechanical ventilation and experience NICU admission..

Unraveling the Role of Maternal Serum Ferritin Levels in Preterm Delivery: A Comprehensive Review

Preterm delivery remains a critical global health concern, with numerous adverse consequences for both neonate and healthcare systems. Understanding the relationship between maternal ferritin levels, as a marker of iron status, and the risk of preterm birth is the focal point of this comprehensive review. We provide insights into the multifaceted nature of this connection, highlighting factors that influence maternal ferritin levels, including dietary intake, genetic and physiological variations, comorbidities, and iron supplementation. While evidence suggests an association between low maternal ferritin levels and preterm birth, causality remains elusive, necessitating further research with robust study designs. The potential mechanisms linking maternal iron status to preterm birth, such as inflammation, infection, and oxidative stress, are explored, underscoring the need for in-depth investigations. This comprehensive review emphasizes the clinical importance of assessing and monitoring maternal ferritin levels in prenatal care and advocates for public health initiatives to raise awareness and provide targeted interventions, particularly in high-risk populations. As we strive to address these unanswered questions and embark on innovative research directions, the aim is to ultimately enhance our understanding of the complex relationship between maternal iron status and preterm birth, leading to improved maternal and child health outcomes.

Safety of influenza vaccination on adverse birth outcomes among pregnant women: A prospective cohort study in Japan

BACKGROUND

Pregnant women are in the highest priority group for receiving influenza vaccination. However, they may be reluctant to receive the vaccination due to concerns about the influence of vaccination on the fetuses.

METHODS

This prospective cohort study of 10 330 pregnant women examined the safety of influenza vaccination in terms of adverse birth outcomes. Influenza vaccination during pregnancy was determined from questionnaires before and after the 2013/2014 influenza season. All subjects were followed until the end of their pregnancy. Adverse birth outcomes, including miscarriage, stillbirth, preterm birth, low birth weight, and malformation, were assessed by obstetrician reports.

RESULTS

Adverse birth outcomes were reported for 641 (10%) of the 6387 unvaccinated pregnant women and 356 (9%) of the 3943 vaccinated pregnant women. Even after adjusting for potential confounders, vaccination during pregnancy showed no association with the risk of adverse birth outcomes (odds ratio 0.90, 95% confidence interval 0.76-1.07). Vaccination during the first or second trimester displayed no association with adverse birth outcomes, whereas vaccination during the third trimester was associated with a decreased risk of adverse birth outcomes (odds ratio 0.70, 95% confidence interval 0.51-0.98).

CONCLUSIONS

Influenza vaccination during pregnancy did not increase the risk of adverse birth outcomes, regardless of the trimester in which vaccination was performed, when compared to unvaccinated pregnant women.

Sex-Gender Variable: Methodological Recommendations for Increasing Scientific Value of Clinical Studies

There is a clear sex-gender gap in the prevention and occurrence of diseases, and in the outcomes and treatments, which is relevant to women in the majority of cases. Attitudes concerning the enrollment of women in randomized clinical trials have changed over recent years. Despite this change, a gap still exists. This gap is linked to biological factors (sex) and psycho-social, cultural, and environmental factors (gender). These multidimensional, entangled, and interactive factors may influence the pharmacological response. Despite the fact that regulatory authorities recognize the importance of sex and gender, there is a paucity of research focusing on the racial/ethnic, socio-economic, psycho-social, and environmental factors that perpetuate disparities. Research and clinical practice must incorporate all of these factors to arrive at an intersectional and system-scenario perspective. We advocate for scientifically rigorous evaluations of the interplay between sex and gender as key factors in performing clinical trials, which are more adherent to real-life. This review proposes a set of 12 rules to improve clinical research for integrating sex-gender into clinical trials.

Association Between Pregnancy and Perinatal Outcomes Among Women With Epilepsy

Importance

To date, few attempts have been made to examine associations between exposure to maternal epilepsy with or without antiepileptic drug (AED) therapy and pregnancy and perinatal outcomes.

Objectives

To investigate associations between epilepsy in pregnancy and risks of pregnancy and perinatal outcomes as well as whether use of AEDs influenced risks.

Design, Setting, and Participants

A population-based cohort study was conducted on all singleton births at 22 or more completed gestational weeks in Sweden from 1997 through 2011; of these, 1 424 279 were included in the sample. Information on AED exposure was available in the subset of offspring from July 1, 2005, to December 31, 2011. Data analysis was performed from October 1, 2016, to February 15, 2017.

Main Outcomes and Measures

Pregnancy, delivery, and perinatal outcomes. Multivariable Poisson log-linear regression was used to estimate adjusted risk ratios (aRRs) and 95% CIs, after adjusting for maternal age, country of origin, educational level, cohabitation with a partner, height, early pregnancy body mass index, smoking, year of delivery, maternal pregestational diabetes, hypertension, and psychiatric disorders.

Results

Of the 1 429 652 births included in the sample, 5373 births were in 3586 women with epilepsy; mean (SD) age at first delivery of the epilepsy cohort was 30.54 (5.18) years. Compared with pregnancies of women without epilepsy, women with epilepsy were at increased risks of adverse pregnancy and delivery outcomes, including preeclampsia (aRR 1.24; 95% CI, 1.07-1.43), infection (aRR, 1.85; 95% CI, 1.43-2.29), placental abruption (aRR, 1.68; 95% CI, 1.18-2.38), induction (aRR, 1.31; 95% CI, 1.21-1.40), elective cesarean section (aRR, 1.58; 95% CI, 1.45-1.71), and emergency cesarean section (aRR, 1.09; 95% CI, 1.00-1.20). Infants of mothers with epilepsy were at increased risks of stillbirth (aRR, 1.55; 95% CI, 1.05-2.30), having both medically indicated (aRR, 1.24; 95% CI, 1.08-1.43) and spontaneous (aRR, 1.34; 95% CI, 1.20-1.53) preterm birth, being small for gestational age at birth (aRR, 1.25; 95% CI, 1.13-1.30), and having neonatal infections (aRR, 1.42; 95% CI, 1.17-1.73), any congenital malformation (aRR, 1.48; 95% CI, 1.35-1.62), major malformations (aRR, 1.61; 95% CI, 1.43-1.81), asphyxia-related complications (aRR, 1.75; 95% CI, 1.26-2.42), Apgar score of 4 to 6 at 5 minutes (aRR, 1.34; 95% CI, 1.03-1.76), Apgar score of 0 to 3 at 5 minutes (aRR, 2.42; 95% CI, 1.62-3.61), neonatal hypoglycemia (aRR, 1.53; 95% CI, 1.34-1.75), and respiratory distress syndrome (aRR, 1.48; 95% CI, 1.30-1.68) compared with infants of unaffected women. In women with epilepsy, using AEDs during pregnancy did not increase the risks of pregnancy and perinatal complications, except for a higher rate of induction of labor (aRR, 1.30; 95% CI, 1.10-1.55).

Conclusions and Relevance

Epilepsy during pregnancy is associated with increased risks of adverse pregnancy and perinatal outcomes. However, AED use during pregnancy is generally not associated with adverse outcomes.

The impact of exposure to antidepressant medications during pregnancy on neonatal outcomes: a review of retrospective database cohort studies

INTRODUCTION

Concerns with prescription antidepressant use in pregnant women have instigated the examination of potential associations between fetal exposure to antidepressant medication and outcomes including preterm delivery, congenital malformations, perinatal and post-natal adverse events, persistent pulmonary hypertension, and mortality. The retrospective cohort model is an often utilized study design. The objective of this review is to evaluate the literature on antidepressant use in pregnancy conducted as retrospective cohorts in national/regional medical, or claims databases that assess neonatal and infant outcomes for agreement between studies, ultimately providing a methodological and outcomes summary for future scientific endeavors.

METHODS

PubMed was searched for literature relating to antidepressant use and infant outcomes from the earliest available date through July 15, 2016. Studies with a retrospective cohort design and conducted in national/regional medical or claims databases were included. Searched outcomes included preterm delivery, congenital malformations, low birth weight, small for gestational age, persistent pulmonary hypertension of the newborn, and other select adverse events comprising low Apgar score (5 min), convulsions/seizures, respiratory distress/problems, fetal mortality, and infant mortality.

RESULTS

Of the 784 studies identified, 36 retrospective cohort studies met eligibility criteria. An increase in preterm delivery and respiratory distress/problems and no increase in congenital malformation or fetal and infant death were associated with prenatal use of prescription antidepressants by majority consensus (at least 2/3 [67%] of studies).

CONCLUSIONS

While consensus indicates that perinatal prescription antidepressant use has consequences for the fetus and infant, there are notable inconsistencies in the literature. More investigations that address prenatal exposure to depression and other important covariates are needed.

Prenatal selective serotonin reuptake inhibitor use and the risk of autism spectrum disorder in children: A systematic review and meta-analysis

OBJECTIVE

To determine whether an up-to-date systematic review and meta-analysis of observational studies would support the previously suggested associations regarding prenatal selective serotonin reuptake inhibitor (SSRI) use and the risk for autism spectrum disorders (ASD) in children.

METHODS

PubMed/MEDLINE, Cochrane Central Register of Controlled Trials and Reprotox databases were searched; observational studies with an exposed and unexposed group were included.

RESULTS

The meta-analysis of case-control studies demonstrated a significantly increased risk of ASD in the children whose mothers were prenatally exposed to SSRIs during different exposure time windows (except third trimester). The qualitative review of the cohort studies suggested inconsistent findings.

CONCLUSIONS

The significant association between preconception-only SSRI exposure and ASD in the children and negative/inconsistent findings among cohort studies weaken the significant associations detected in this meta-analysis. We suggest that confounding by indication still cannot be ruled out regarding prenatal SSRI exposure and ASD in children.

Constructing Causal Diagrams for Common Perinatal Outcomes: Benefits, Limitations and Motivating Examples with Maternal Antidepressant Use in Pregnancy

BACKGROUND

Covariate selection to reduce bias in observational data analysis has primarily relied upon statistical criteria to guide researchers. This approach may lead researchers to condition on variables that ultimately increase bias in the effect estimates. The use of directed acyclic graphs (DAGs) aids researchers in constructing thoughtful models based on hypothesised biologic mechanisms to produce the least biased effect estimates possible.

METHODS

After providing an overview of different relations in DAGs and the prevailing mechanisms by which conditioning on variables increases or reduces bias in a model, we illustrate examples of DAGs for maternal antidepressants in pregnancy and four separate perinatal outcomes.

RESULTS

By comparing and contrasting the diagrams for maternal antidepressant use in pregnancy and spontaneous abortion, major malformations, preterm birth, and postnatal growth, we illustrate the different conditioning sets required for each model. Moreover, we illustrate why it is not appropriate to condition on the same set of covariates for the same exposure and different perinatal outcomes. We further discuss potential selection biases, overadjustment of mediators on the causal path, and sufficient sets of conditioning variables.

CONCLUSION

In our efforts to construct parsimonious models that minimise confounding and selection biases, we must rely upon our scientific knowledge of the causal mechanism. By structuring data collection and analysis around hypothesised DAGs, we ultimately aim to validly estimate the causal effect of interest.

Risk of Preterm or Small-for-Gestational-Age Birth After Influenza Vaccination During Pregnancy: Caveats When Conducting Retrospective Observational Studies

Vaccines are increasingly targeted toward women of reproductive age, and vaccines to prevent influenza and pertussis are recommended during pregnancy. Prelicensure clinical trials typically have not included pregnant women, and when they are included, trials cannot detect rare events. Thus, postmarketing vaccine safety assessments are necessary. However, analysis of observational data requires detailed assessment of potential biases. Using data from 8 Vaccine Safety Datalink sites in the United States, we analyzed the association of monovalent H1N1 influenza vaccine (MIV) during pregnancy with preterm birth (<37 weeks) and small-for-gestational-age birth (birth weight < 10th percentile). The cohort included 46,549 pregnancies during 2009-2010 (40% of participants received the MIV). We found potential biases in the vaccine-birth outcome association that might occur due to variable access to vaccines, the time-dependent nature of exposure to vaccination within pregnancy (immortal time bias), and confounding from baseline differences between vaccinated and unvaccinated women. We found a strong protective effect of vaccination on preterm birth (relative risk = 0.79, 95% confidence interval: 0.74, 0.85) when we ignored potential biases and no effect when accounted for them (relative risk = 0.91; 95% confidence interval: 0.83, 1.0). In contrast, we found no important biases in the association of MIV with small-for-gestational-age birth. Investigators conducting studies to evaluate birth outcomes after maternal vaccination should use statistical approaches to minimize potential biases.

The association of episiotomy with obstetric anal sphincter injury--a population based matched cohort study

OBJECTIVES

To estimate the independent association of episiotomy with obstetric anal sphincter injuries (OASIS) using first a cross-sectional and then a matched pair analysis.

DESIGN

A matched cohort.

SETTING

Data was gathered from the Finnish Medical Birth Register from 2004-2011.

POPULATION

All singleton vaginal births (n = 303,758).

METHODS

Women resulting matched pairs (n = 63,925) were matched based on baseline risk of OASIS defined based on parity (first or second/subsequent vaginal births), age, birth weight, mode of delivery, prior caesarean section, and length of active second stage of birth.

RESULTS

In cross-sectional analysis episiotomy was associated with a 12% lower incidence of OASIS (adjusted odds ratio (aOR) 0.88, 95% confidence interval (CI) 0.80 to 0.98) in first vaginal births and with a 132% increased incidence of OASIS in second or subsequent vaginal births (aOR 2.32, 95% CI 1.77 to 3.03). In matched pair analysis episiotomy was associated with a 23% (aOR 0.77, 95% CI 0.69 to 0.86) lower incidence of OASIS in first vaginal births and a 61% (aOR 1.61, 95% CI 1.14 to 2.29) increased incidence of OASIS in second or subsequent vaginal births compared to women who gave birth without an episiotomy. The matched pair analysis showed a 12.5% and a 31.6% reduction in aORs of OASIS associated with episiotomy, respectively.

CONCLUSIONS

A matched pair analysis showed a substantial reduction in the aORs of OASIS with episiotomy, due to confounding by indication. This indicates that results of observational studies evaluating an association between episiotomy and OASIS should be interpreted with caution.

Maternal influenza vaccine and risks for preterm or small for gestational age birth

OBJECTIVE

To study the impact of influenza vaccine administered to pregnant women during all trimesters on the rates of preterm and small for gestational age (SGA) births, evaluating both increased and decreased risk.

STUDY DESIGN

This retrospective observational matched cohort study involved 7 Vaccine Safety Datalink sites across the US for the 2004-05 through 2008-09 influenza seasons. Cohort eligibility and outcomes were determined from administrative, claims, medical records, and birth data. In propensity score- and vaccine exposure time-matched analyses, ORs for preterm and SGA births were calculated.

RESULTS

Among 57 554 matched vaccinated and unvaccinated pregnant women, including 16 240 women in the first trimester, maternal vaccination was not associated with increased or decreased risk for preterm birth (OR for delivery at <37 weeks gestation, 0.97 [95% CI, 0.93-1.02]; for delivery at ≤32 weeks gestation, 0.98 [95% CI, 0.86-1.12]; and for delivery at ≤34 weeks gestation, 0.96 [95% CI, 0.88-1.04]) or SGA birth (OR for <5th percentile weight for gestational age, 1.02 [95% CI, 0.96-1.09], and for <10th percentile weight for gestational age, 1.00 [95% CI, 0.96-1.04]). Similarly, first trimester vaccination was not associated with increased or decreased risk for preterm or SGA birth.

CONCLUSION

Receipt of trivalent inactivated influenza vaccine during pregnancy was not associated with increased or decreased risk of preterm or SGA birth. These findings support the safety of vaccinating pregnant women against influenza during the first, second, and third trimesters, and suggest that a nonspecific protective effect of the influenza vaccine for these outcomes does not exist.