Prescription drug use in pregnancy: more evidence of safety is needed

A potential outcomes approach to defining and estimating gestational age-specific exposure effects during pregnancy

Many studies seek to evaluate the effects of potentially harmful pregnancy exposures during specific gestational periods. We consider an observational pregnancy cohort where pregnant individuals can initiate medication usage or become exposed to a drug at various times during their pregnancy. An important statistical challenge involves how to define and estimate exposure effects when pregnancy loss or delivery can occur over time. Without proper consideration, the results of standard analysis may be vulnerable to selection bias, immortal time-bias, and time-dependent confounding. In this study, we apply the “target trials” framework of Hernán and Robins in order to define effects based on the counterfactual approach often used in causal inference. This effect is defined relative to a hypothetical randomized trial of timed pregnancy exposures where delivery may precede and thus potentially interrupt exposure initiation. We describe specific implementations of inverse probability weighting, G-computation, and Targeted Maximum Likelihood Estimation to estimate the effects of interest. We demonstrate the performance of all estimators using simulated data and show that a standard implementation of inverse probability weighting is biased. We then apply our proposed methods to a pharmacoepidemiology study to evaluate the potentially time-dependent effect of exposure to inhaled corticosteroids on birthweight in pregnant people with mild asthma.

Trends and Determinants of Prescription Drug Use during Pregnancy and Postpartum in British Columbia, 2002-2011: A Population-Based Cohort Study

Purpose

To describe trends, patterns, and determinants of prescription drug use during pregnancy and postpartum.

Methods

This is a retrospective, population-based study of all women who gave birth between January 2002 and 31 December 2011 in British Columbia, Canada. Study population consisted of 225,973 women who had 322,219 pregnancies. We examined administrative datasets containing person-specific information on filled prescriptions, hospitalizations, and medical services. Main outcome measures were filled prescriptions during pregnancy and postpartum. We used logistic regressions to examine associations between prescription drug use and maternal characteristics.

Results

Approximately two thirds of women filled a prescription during pregnancy, increasing from 60% in 2002 to 66% in 2011. The proportion of pregnant women using medicines in all three trimesters of pregnancy increased from 20% in 2002 to 27% in 2011. Use of four or more different types of prescription drug during at least one trimester increased from 8.4% in 2002 to 11.7% in 2011. Higher BMI, smoking during pregnancy, age under 25, carrying multiples, and being diagnosed with a chronic condition all significantly increased the odds of prescription drug use during pregnancy.

Conclusions

The observed increase in the number of prescriptions and number of different drugs being dispensed suggests a trend in prescribing practices with potentially important implications for mothers, their neonates, and caregivers. Monitoring of prescribing practices and further research into the safety of most commonly prescribed medications is crucial in better understanding risks and benefits to the fetus and the mother.

Prescriptions for category D and X drugs during pregnancy in Taiwan: a population-based study

PURPOSE

This study aimed to investigate the most prescribed medications and principle diagnoses for category D and X drugs during pregnancy using a population-based dataset in Taiwan.

METHODS

The data for the present study were sourced from the Taiwan Longitudinal Health Insurance Database 2000. We selected 14 125 women who had live singleton births between 1 January 2009 and 31 December 2011. In total, 217 226 prescriptions prescribed to these pregnant women were identified.

RESULTS

Of the total 217 226 prescriptions, 1.1% were category D or X drugs; in the first, second, and third trimesters of pregnancy, 1.8%, 0.7%, and 0.5% of prescriptions were category D or X drugs, respectively. Progestins (15.3%) and propylthiouracil (10.7%) were the two most frequently prescribed category D or X drugs during pregnancy. In particular, progestins (20.4%) and estrogens (15.6%) were the most frequently prescribed category D or X drug in the first trimester of pregnancy. Propylthiouracil was the most prescribed category D or X drug in the second (20.3%) and third trimesters (23.1%) of pregnancy, respectively. The most common principal diagnosis during pregnancy was "disorders of menstruation and other abnormal bleeding from the female genital tract" (22% of all principal diagnoses for prescribing category D and X drugs).

CONCLUSIONS

Our study found that the physicians obviously reduced the use of category D and X drugs for women after becoming aware that they were pregnant.