342: The effect of opioid exposure in utero on neonatal body composition

Abstract

Opioid use in pregnancy has been associated with low birth weight as well as reduced head circumference. Whether these differences are due to changes neonatal body composition (i.e. lean mass and fat mass) has not been established. The goal of this study is to investigate the differences in body composition among neonates exposed to opioids in utero, compared with those who are not exposed. This is a retrospective cohort study of singleton pregnancies delivered at term. Subjects with opioid exposure during pregnancy were identified and subjects without opioid exposure were used for comparison. Exposed subjects were matched 1:2 with unexposed subjects for variables known to affect neonatal body composition; this included gestational age at delivery (±7 days), neonatal sex, smoking, and maternal race. Neonatal anthropometric measurements and skin fold data were used to determine neonatal percent body fat. Anthropometric data was expressed as mean ± SD and analyzed by Mann-Whitney U test. Demographic data was compared using Student’s t test and chi-squared analysis where appropriate. All statistical analysis performed using R statistical software. P <0.05 was considered significant. 24 neonates exposed to opioids in utero were identified and matched with 48 unexposed neonates. The groups were similar in terms of maternal age, race, neonatal sex, and gestational age at delivery. The exposed versus unexposed subjects differed in maternal BMI at delivery (28.4 vs 35.3, p = 0.001), gestational weight gain (14.3 lb vs 28.6 lb, p = <0.05), nulliparity (17% vs 48%, p = 0.02) and smoking status (66% vs 33%, p = 0.02). The analysis of our results did not demonstrate a statistically significant difference in birth weight, skin fold measurement, fat mass, lean mass, or percent body fat between the two groups. However, we found birth length and head circumference to be significantly different (p = 0.03 for both, Table 1). In this cohort, opioid exposure in utero was not associated with changes in neonatal body composition. However, we identified statically significant decreases in birth length and head circumference when compared with unexposed neonates. This work suggests that opioid exposure does not affect neonatal body composition but may impact other neonatal anthropometric measures.