Prenatal medication use in a prospective pregnancy cohort by pre-pregnancy obesity status.

BACKGROUND The association between obesity (body mass index (BMI) ≥ 30 kg/m2) and pattern of medication use during pregnancy in the United States is not well-studied. Higher pre-pregnancy BMI may be associated with increases or decreases in medication use across pregnancy as symptoms (e.g. reflux) or comorbidities (e.g. gestational diabetes) requiring treatment that may be associated with higher BMI could also change with advancing gestation. OBJECTIVES To determine whether prenatal medication use, by the number and types of medications, varies by pre-pregnancy obesity status. METHODS In a secondary data analysis of a racially/ethnically diverse prospective cohort of pregnant women with low risk for fetal abnormalities enrolled in the first trimester of pregnancy and followed to delivery (singleton, 12 United States clinical sites), free text medication data were obtained at enrollment and up to five follow-up visits and abstracted from medical records at delivery. RESULTS In 436 women with obesity and 1750 women without obesity (pre-pregnancy BMI, 19-29.9 kg/m2), more than 70% of pregnant women (77% of women with and 73% of women without obesity) reported taking at least one medication during pregnancy, respectively (adjusted risk ratio (aRR)=1.10, 95% confidence interval (CI)=1.01, 1.20), with 81% reporting two and 69% reporting three or more. A total of 17 classes of medications were identified. Among medication classes consumed by at least 5% of all women, the only class that differed between women with and without obesity was hormones and synthetic substitutes (including steroids, progesterone, diabetes, and thyroid medications) in which women with obesity took more medications (11 vs. 5%, aRR = 1.9, 95% CI = 1.38, 2.61) compared to women without obesity. Within this class, a higher percentage of women with obesity took diabetes medications (2.3 vs. 0.7%) and progesterone (3.4 vs. 1.3%) than their non-obese counterparts. Similar percentages of women with and without obesity reported consuming medications in the remaining medication classes including central nervous system agents (50 and 46%), gastrointestinal drugs (43 and 40%), anti-infective agents (23 and 21%), antihistamines (20 and 17%), autonomic drugs (10 and 9%), and respiratory tract agents (7 and 6%), respectively (p > 0.05 for all adjusted comparisons). There were no differences in medication use by obesity status across gestation. Since the study exclusion criteria limited the non-obese group to women without thyroid disease, in a sensitivity analysis we excluded all women who reported thyroid medication intake and still a higher proportion of women with obesity took the hormones and synthetic substitutes class compared to women without obesity. CONCLUSION Our findings suggest that pre-pregnancy obesity in otherwise healthy women is associated with a higher use of only selected medications (such as diabetes medications and progesterone) during pregnancy, while the intake of other more common medication types such as analgesics, antibiotics, and antacids does not vary by pre-pregnancy obesity status. As medication safety information for prenatal consumption is insufficient for many medications, these findings highlight the need for a more in-depth examination of factors associated with prenatal medication use.