Multistate methodology improves risk assessment under time‐varying drug intake—a new view on pregnancy outcomes following coumarin exposure

Impact of maternal first trimester treatment regimen on the outcome of valproate exposed pregnancies: an observational Embryotox cohort study

Effects of valproate (VPA) dose and treatment discontinuation during the first trimester of pregnancy on the risks of spontaneous abortions (SAB) and major birth defects were analyzed. Pregnancies with first trimester VPA exposure (n = 484) prospectively recorded by the German Embryotox center in 1997-2016 were compared with a randomly selected, non-exposed cohort (n = 1446). The SAB risk was not significantly increased in the VPA cohort [HRadj 1.31 (95% CI 0.85-2.02)] but major birth defects were significantly more frequent [8.7% vs. 3.4%; ORadj 2.61 (95% CI 1.51-4.50)]. Risk was even higher in pregnancies with no VPA discontinuation in first trimester [ORadj 3.66 (95% CI 2.04-6.54)]. Significant ORs were found for nervous system defects in general [ORadj 5.69 (95% CI 1.73-18.78)], severe microcephaly [ORadj 6.65 (95% CI 1.17-37.68)], hypospadias [ORadj 19.49 (95% CI 1.80-211)] and urinary system defects [ORadj 6.51 (95% CI 1.48-28.67)]. VPA dose had a stronger effect than antiepileptic poly- versus monotherapy; for VPA dose ≥ 1500 mg/day the ORadj was 5.41 (95% CI 2.32-12.66)]. A daily dose increase of 100 mg was calculated to raise the risk for major birth defects by 15% [OR 1.15 (95% CI 1.08-1.23)]. Overall, maternal first trimester treatment regimen had a relevant impact on birth defect risk.

How to account for early overly small risk sets in the analysis of pregnancy outcome data?-Comparison of different methods for stabilizing the Aalen-Johansen estimator

PURPOSE

In analyzing pregnancy data concerning drug exposure in the first trimester, the risk of spontaneous abortions is of primary interest. For estimating the cumulative incidence function, the Aalen-Johansen estimator is typically used, and competing risks such as induced abortion and livebirth are considered. However, the delayed study entry can lead to overly small risk sets for the first events. This results in large jumps in the estimated cumulative incidence function of spontaneous abortions or induced abortions using the Aalen-Johansen estimator, and consequently in an overestimation of the probability.

METHODS

Several approaches account for early overly small risk sets. The first approach is conditioning on the event time being greater than the event time causing the large jump. Second, the events can be ignored by censoring them. Third, the events can be postponed until a large enough number is at risk. These three approaches are compared.

RESULTS

All approaches are applied using data of 54 lacosamide-exposed pregnancies. The Aalen-Johansen estimate of the probability of spontaneous abortion is 22.64%, which is relatively large for only three spontaneous abortions in the dataset. The conditional approach and the ignore approach have an estimated probability of 7.17%. In contrast, the estimate of the postpone approach is 16.45%. In this small sample, bootstrapped confidence intervals seem more accurate.

CONCLUSIONS

In the analyses of pregnancy data with rare events, the postpone approach is favorable as no events are excluded. However, the approach that ignores early events has the narrowest confidence interval.

Effects of maternal modafinil treatment on fetal development and neonatal growth parameters - a multicenter case series of the European Network of Teratology Information Services (ENTIS)

OBJECTIVE

In recent years, safety concerns about modafinil exposure during pregnancy have emerged. In particular, increased risks for major congenital anomalies (MCA) and impaired fetal growth were reported, although study results were conflicting. Our investigation aims to examine previously reported safety signals.

METHOD

Multicenter case series based on data from 18 Teratology Information Services from 12 countries. Modafinil exposed pregnancies with an estimated date of birth before August 2019 were included in this study. For prospectively ascertained pregnancies, cumulative incidences of pregnancy outcomes, rate of nonchromosomal MCA in first trimester exposed pregnancies and percentiles of neonatal/infant weight and head circumference (HC) were calculated. Potential dose-dependent effects on fetal growth were explored by linear regression models. Retrospectively ascertained cases were screened for pattern of MCA and other adverse events.

RESULTS

One hundred and seventy-five prospectively ascertained cases were included, of which 173 were exposed at least during the first trimester. Cumulative incidences for live birth, spontaneous abortion and elective termination of pregnancy were 76.9% (95% CI, 68.0%-84.8%), 9.3% (95% CI, 5.0%-16.9%), and 13.9% (95% CI, 8.1%-23.1%), respectively. Nonchromosomal MCA was present in 3/150 live births, corresponding to an MCA rate of 2.0% (95%CI, 0.6%-6.1%), none were reported in pregnancy losses. Compared to reference standards, birth weight (BW) tended to be lower and neonatal HC to be smaller in exposed newborns (data available for 144 and 73 of 153 live births, respectively). In nonadjusted linear regression models, each 100 mg increase of average dosage per pregnancy day was associated with a decrease in standard deviation score (SDS) of -0.28 SDS (95% CI, -0.45 to -0.10) for BW and of -0.28 SDS (95% CI, -0.56 to 0.01) for HC. Screening of 22 retrospectively reported cases did not reveal any specific pattern of MCA or other adverse outcomes.

CONCLUSION

The results do not indicate an increased risk of MCA after in utero exposure to modafinil, but a tendency toward lower BW and reduced neonatal HC. However, these findings should be regarded as preliminary. Until further studies allow for a definite conclusion, modafinil should not be used during pregnancy.

Longitudinal Methods for Modeling Exposures in Pharmacoepidemiologic Studies in Pregnancy

In many perinatal pharmacoepidemiologic studies, exposure to a medication is classified as "ever exposed" versus "never exposed" within each trimester or even over the entire pregnancy. This approach is often far from real-world exposure patterns, may lead to exposure misclassification, and does not to incorporate important aspects such as dosage, timing of exposure, and treatment duration. Alternative exposure modeling methods can better summarize complex, individual-level medication use trajectories or time-varying exposures from information on medication dosage, gestational timing of use, and frequency of use. We provide an overview of commonly used methods for more refined definitions of real-world exposure to medication use during pregnancy, focusing on the major strengths and limitations of the techniques, including the potential for method-specific biases. Unsupervised clustering methods, including k-means clustering, group-based trajectory models, and hierarchical cluster analysis, are of interest because they enable visual examination of medication use trajectories over time in pregnancy and complex individual-level exposures, as well as providing insight into comedication and drug-switching patterns. Analytical techniques for time-varying exposure methods, such as extended Cox models and Robins' generalized methods, are useful tools when medication exposure is not static during pregnancy. We propose that where appropriate, combining unsupervised clustering techniques with causal modeling approaches may be a powerful approach to understanding medication safety in pregnancy, and this framework can also be applied in other areas of epidemiology.

First trimester naproxen exposure and outcome of pregnancy - A German case series

In contrast to other non-steroidal anti-inflammatory drugs (NSAIDs), naproxen use during pregnancy is not well studied. The objective of this analysis was to assess negative effects on pregnancy outcomes following naproxen exposure in the first trimester of pregnancy. Out of 121 exposed pregnancies prospectively recorded by two German teratology information services (TIS) 15 ended as spontaneous abortion and ten were electively terminated; in one case for prenatal diagnosis of anencephaly. Four pregnancies were stillborn, in these cases naproxen was discontinued more than two months before the event. Of 95 live-born infants, including three pairs of twins, two were born with major birth defects: one with dysmelia of the left hand and foot and another with a complex congenital heart defect, esophageal atresia with tracheoesophageal fistula, and choanal stenosis. The results of this case series do not suggest that naproxen has a significant teratogenic effect. However, due to the limited cohort size and lack of comparable reference group results should be interpreted with caution and better studied NSAIDs such as ibuprofen should be preferred in the first and second trimester of pregnancy. This work was supported by the German Federal Institute for Drugs and Medical Devices (BfArM).

Bootstrapping complex time-to-event data without individual patient data, with a view toward time-dependent exposures

We consider nonparametric and semiparametric resampling of multistate event histories by simulating multistate trajectories from an empirical multivariate hazard measure. One advantage of our approach is that it does not necessarily require individual patient data, but may be based on published information. This is also attractive for both study planning and simulating realistic real-world event history data in general. The concept extends to left-truncation and right-censoring mechanisms, nondegenerate initial distributions, and nonproportional as well as non-Markov settings. A special focus is on its connection to simulating survival data with time-dependent covariates. For the case of qualitative time-dependent exposures, we demonstrate that our proposal gives a more natural interpretation of how such data evolve over the course of time than many of the competing approaches. The multistate perspective avoids any latent failure time structure and sampling spaces impossible in real life, whereas its parsimony follows the principle of Occam's razor. We also suggest empirical simulation as a novel bootstrap procedure to assess estimation uncertainty in the absence of individual patient data. This is not possible for established procedures such as Efron's bootstrap. A simulation study investigating the effect of liver functionality on survival in patients with liver cirrhosis serves as a proof of concept. Example code is provided.

Pregnancy outcome after first-trimester exposure to fosfomycin for the treatment of urinary tract infection: an observational cohort study

PURPOSE

The primary aim of our study was to assess pregnancy outcome after first-trimester exposure to fosfomycin.

METHODS

We performed an observational cohort study analysing prospectively ascertained pregnancies including 152 women exposed to fosfomycin in the first trimester of pregnancy in comparison with a randomly selected cohort comprising 456 pregnancies not exposed to fosfomycin. All pregnancies were identified through risk consultations using structured questionnaires between January 2000 and December 2016 by the German Embryotox pharmacovigilance institute in Berlin. Primary objectives were the risks of major birth defects and spontaneous abortion.

RESULTS

Only 1 out of 146 exposed infants was affected by a major birth defect (0.7%, 95% CI 0.04-4.33%) in comparison to 15/399 in the non-exposed cohort (3.8%, 95% CI 2.2-6.26%). Spontaneous abortions were observed in 5/152 cases in the fosfomycin cohort vs. 53/456 cases in the comparison cohort (cumulative incidence 6.2% vs. 23.1%; HR adjusted 0.35, 95% CI 0.14-0.90).

CONCLUSION

This is the first study specifically examining the teratogenic risk of fosfomycin. The study results do not indicate an increased risk of adverse pregnancy outcome after fosfomycin exposure during early pregnancy. However, larger studies are needed to confirm the safety of fosfomycin during the first trimester.