Participants
We identified 201 pregnancies exposed to the BDZ group and 386 pregnancies not exposed to BDZ in the period of interest. In the exposed group, six pregnancies were excluded because of multiple births and one for a stillbirth. Of the remaining 194 singleton live birth pregnancies in the exposed group, a total of 25 pregnancies were excluded for the following reasons: pregnancies with an actual diagnosis of epilepsy, pregnancies with congenital malformations in one of the parents, or exposure to teratogenic drugs. For the same reasons and due to missing data about the primary and secondary outcomes, 42 pregnancies were excluded and nine multiple births pregnancies from the reference group.
As a result, 169 pregnancies in the exposed group and 335 pregnancies in the reference group were eligible. In presence of more than one pregnancy from the same mother we randomly selected a pregnancy in our dataset. See figure 1 for the details on patient selection. The final dataset consisted of 147 pregnancies in the exposed group and 294 pregnancies in the reference group.
Both groups differed in maternal and clinical characteristics, see table 1. In the BDZs exposed women used more alcohol during pregnancy (4.1% vs 0.7%, p = 0.019), had lower number of mental disorders (p=0.010), a higher number of concomitant psychotropics (p<0.001), and needed longer psychiatric care after delivery (p<0.001), see table 1. Duration of pregnancy was shorter in the BDZs exposed group, 269 days for the exposed group and 274 days for the non-exposed group, p<0.001.