OBJECTIVE:

To measure the association between the class of antidepressant (AD) used according to trimester of exposure during pregnancy and infants born small for gestational age (SGA).

METHODS:

A case-control study was performed using data from the Quebec Pregnancy Registry, which includes 152,107 pregnant women between January 1, 1998, and December 31, 2002. For this study, eligible women were aged 15 to 45 years on the first day of gestation, had drug plan coverage from the Régie de l'Assurance Maladie du Québec for 12 months or more prior to and during pregnancy, had at least 1 psychiatric disorder diagnosis before pregnancy, used ADs for at least 30 days in the year prior to pregnancy, and delivered a live singleton. AD exposure during pregnancy was defined according to trimester of use and class (selective serotonin reuptake inhibitors [SSRIs], tricyclic AD, or other ADs). SGA cases were defined as newborns with a birth weight of less than the 10th percentile according to Canadian charts. Relative risks, adjusted for potential confounders, were estimated using modified Poisson regression.

RESULTS:

Among the 938 eligible pregnancies, 128 (13.6%) infants were born SGA. Other ADs, mainly venlafaxine, used by women during the second trimester were associated with an increased risk of infants born SGA, compared with nonusers of ADs (adjusted relative risk = 2.41; 95% CI 1.07 to 5.43). Regardless of the trimester of use, no association was found between SSRIs or tricyclics and the risk of SGA.

CONCLUSIONS:

This study suggests that use of venlafaxine during the second trimester of pregnancy may increase the risk of infants born SGA.