Authors' reply

We would like to emphasise that our study included nationwide data on the use of all antidepressants in Denmark wherever prescribed (including from primary care), however nationwide data on the diagnosis of depression were only available from in-patient and out-patient psychiatric hospital settings (and not from primary care). Thus, as argued in our paper, we believe our findings can be generalised to all women taking antidepressants during pregnancy regardless of the indication for treatment (depression, anxiety disorder, etc.) or the severity of illness.

Although, the study included more than 34 000 women who used an antidepressant before or during pregnancy, this number was too small for separate analyses of the individual antidepressants divided into the eight risk groups defined in the study. Register-based medication studies at present do not have access to data on the dose of drug treatment or on patient adherence to the drug. We did try to adjust our analyses for physical disorder in the mother as all analyses were adjusted for all other types of medication (in addition to antidepressants) that the mother may have used during pregnancy, in this way taking account of treated physical and mental disorders as well as depressive and anxiety disorders. We further adjusted analyses for maternal age, employment status, smoking status, calendar year, parity, gender of the newborn, ±birth weight and ±gestational age, however we did not include data on nutrition of the mother and on obstetric complications as suggested. Obstetric complications may rather be intermediary factors than confounders.

Regarding the gestational age of all mothers, this was correctly indicated in Table 1 as a median of 39 (interquartiles 39-39), as infants with a gestational age less than 22 weeks were excluded from analyses and the vast majority of children were born within week 39.

Like Nebhinani & Soni, we hope the study will provide impetus for future research in this increasingly important area, especially as the use of antidepressants during pregnancy is believed to increase even further in the future.