Objective: Previous research reported greater risk of adverse perinatal outcomes associated with first trimester exposure to angiotensin converting enzyme inhibitors (ACEIs) in comparison to unexposed pregnancies among non-hypertensive women. We examined the relationship between first trimester exposure to ACEIs and angiotensin receptor blockers (ARBs), and maternal and perinatal outcomes, whilst controlling for the underlying hypertension.

Study design: We performed a population-based cohort study among 130,061 pregnancies resulting in birth in NSW, Australia between 2005 and 2012. Birth data were linked to hospital discharge and pharmaceutical dispensing records. After restricting to women with chronic hypertension, 67 and 73 pregnancies exposed to ACEIs and ARBs respectively during the first trimester were compared with 316 pregnancies exposed to methyldopa.

Study outcomes: Preterm delivery, caesarean section, low birth weight, small for gestational age and Apgar score <7.

Results: Compared to pregnancies exposed to methyldopa, the adjusted odds ratio (aOR) for ACEI exposure was 0.5 (95% CI: 0.2-1.1) for preterm delivery, 1.6 (0.8-3.1) for caesarean section, 0.6 (0.2-1.3) for LBW and 0.8 (0.4-1.9) for SGA. The corresponding aORs and confidence intervals for ARB exposure were 0.7 (0.3-1.5), 1.2 (0.6-2.6), 1.3 (0.7-2.6), and 1.2 (0.6-2.4).

Conclusion: No association between early pregnancy exposure to ACEIs and ARBs and perinatal outcomes was observed, however, the possibility of an association cannot be ruled out due to limited power. Nonetheless, this study suggests that the magnitude of risk is smaller than that reported previously.