Objective: To determine if prenatal exposure to methylphenidate (MPH) or atomoxetine (ATX) increases the risk of adverse pregnancy outcomes in women with attention deficit/hyperactivity disorder (ADHD).
Materials and methods: This was a population-based cohort study of all pregnancies in Denmark from 1997 to 2008. Information on use of ADHD medication, ADHD diagnosis, and pregnancy outcomes was obtained from nationwide registers.
Results: We identified 989,932 pregnancies, in which 186 (0.02%) women used MPH/ATX and 275 (0.03%) women had been diagnosed with ADHD but who did not take MPH/ATX. Our reference pregnancies had no exposure to MPH/ATX and no ADHD diagnosis. Exposure to MPH/ATX was associated with an increased risk of spontaneous abortion (SA; ie, death of an embryo or fetus in the first 22 weeks of gestation) (adjusted relative risk [aRR] 1.55, 95% confidence interval [CI] 1.03-2.36). The risk of SA was also increased in pregnancies where the mother had ADHD but did not use MPH/ATX (aRR 1.56, 95% CI 1.11-2.20). The aRR of Apgar scores <10 was increased among exposed women (aRR 2.06, 95% CI 1.11-3.82) but not among unexposed women with ADHD (aRR 0.99, 95% CI 0.48-2.05).
Conclusion: MPH/ATX was associated with a higher risk of SA, but our study indicated that it may at least partly be explained by confounding by indication. Treatment with MPH/ATX was however associated with low Apgar scores <10, an association not found among women with ADHD who did not use MPH/ATX.
Keywords: ADHD; atomoxetine; attention deficit/hyperactivity disorder; methylphenidate; pregnancy outcomes.