Drug exposure in pregnant women

Bayesian hierarchical methods in the detection of potentially teratogenic first-trimester medications

PURPOSE

Bayesian hierarchical models (BHMs) have been used to identify adverse drug reactions, allowing information sharing amongst adverse reactions and drugs expected to have similar properties. This study evaluated the use of BHMs in the routine signal detection analyses of potential first-trimester teratogens, where these models have not previously been applied.

METHODS

Data on 15 058 malformed foetuses exposed to first trimester medications (1995-2011) from 13 European congenital anomaly (CA) registries were analysed. The proportion of each CA in women taking a specific medication was compared with the proportion of that CA in all other women in the dataset (55 CAs × 523 medications). BHMs were grouped by either medications or CAs or by both simultaneously, and the results compared with analysing each medication-CA combination separately and adjusting for multiplicity using a double false discovery rate (FDR) procedure. The proportions of "high-risk" medications (medications which have been shown to carry a moderate to high risk of foetal malformations) identified as potential signals were compared, as well as the total number of potential signals requiring follow up (the effective workload).

RESULTS

BHMs identified more high-risk medications than the double FDR method, but the effective workload was larger. A BHM grouping both medications and CAs, for example, identified 23% of high-risk medications compared with 14% by the double FDR; however, there was an increase from 16 to 71 potential signals requiring follow up.

CONCLUSION

For comparable effective workloads, BHMs did not outperform the double FDR, which is comparatively straightforward to implement and is therefore recommended for continued use in teratogenic signal detection analyses.

[Use of medicines before and during pregnancy: prevalence and associated factors]

This cross-sectional prospective nested cohort study aimed to assess the prevalence of use of medication before and during pregnancy and associated factors in women in a municipality in the countryside of Bahia State, Brazil. Data were collected with a structured questionnaire applied to pregnant women at their prenatal visits at health units. Prevalence rates for use of medication before and during pregnancy were 52.1% and 84.7%, respectively. The following were associated with use of medication before pregnancy: age ≥ 30 years, non-white skin color, first prenatal visit after the 1st trimester, and economic classes C/D/E. There was an increase in medication during pregnancy among women with ≥ 11 years of schooling, women with more than three prenatal visits, and those with some health problem. Pregnant women are exposed to medication before and during pregnancy, notwithstanding the lack of secure information to back the use of medicines during this phase; such use is associated with factors pertaining to prenatal follow-up, suggesting the need for more active participation by pharmacists in orientation and support for rational use of medicines.

Risk and benefit of drug use during pregnancy

Environmental teratogenic factors (e.g. alcohol) are preventable. We focus our analysis on human teratogenic drugs which are not used frequently during pregnancy. The previous human teratogenic studies had serious methodological problems, e.g. the first trimester concept is outdated because environmental teratogens cannot induce congenital abnormalities in the first month of gestation. In addition, teratogens usually cause specific congenital abnormalities or syndromes. Finally, the importance of chemical structures, administrative routes and reasons for treatment at the evaluation of medicinal products was not considered. On the other hand, in the so-called case-control epidemiological studies in general recall bias was not limited. These biases explain that the teratogenic risk of drugs is exaggerated, while the benefit of medicine use during pregnancy is underestimated. Thus, a better balance is needed between the risk and benefit of drug treatments during pregnancy. Of course, we have to do our best to reduce the risk of teratogenic drugs as much as possible, however, it is worth stressing the preventive effect of drugs for maternal diseases (e.g. diabetes mellitus and hyperthermia) related congenital abnormalities.