Venlafaxine

Pregnancy

Miscarriage: MotherToBaby says one study suggested a higher chance, while other studies did not, and says depression itself may also affect the chance. In a Quebec nested case-control study of 5,124 pregnancies ending in miscarriage, venlafaxine use was associated with spontaneous abortion (adjusted OR 2.11, 95% CI 1.34 to 3.30; Nakhai-Pour 2010). A prospective comparative study of 281 venlafaxine-exposed pregnancies found no statistically significant difference in spontaneous abortion versus antidepressant-unexposed pregnancies after adjustment for timing and competing outcomes (HR 1.28, 95% CI 0.85 to 1.94; Richardson 2019). These observational studies do not establish cause. Birth defects: a 2016 systematic review of eight cohort studies pooled 3,186 venlafaxine-exposed infants and 107 major malformations; its estimated RR was 1.12 (95% CI 0.92 to 1.35), which did not show a statistically significant increase (Lassen 2016). A large Nordic study found that the initial associations for cardiac defects weakened in sibling-controlled analyses (Furu 2015). A US case-control study found associations between venlafaxine and several specific defects, but its authors said these findings need confirmation because the venlafaxine literature is limited (Anderson 2020). MotherToBaby reports mixed findings for preterm birth and gestational diabetes, and says depression may also contribute to pregnancy complications. A 2019 Quebec case-control study found an association between venlafaxine and gestational diabetes (aOR 1.27, 95% CI 1.09 to 1.49; Dandjinou 2019), while a 2019 cohort comparing antidepressant continuers with discontinuers found a venlafaxine-specific estimate that was not statistically significant (RR 1.52, 95% CI 0.87 to 2.68). A 2026 FAERS analysis flagged venlafaxine among potential gestational-diabetes signals; FAERS reports do not provide a rate among treated pregnancies or establish causation. The current label says venlafaxine use in mid-to-late pregnancy may increase preeclampsia risk and use in the month before delivery may be associated with postpartum hemorrhage. A 2025 maternal-fetal pharmacokinetic model and a 2026 neonatal FAERS analysis add signals but do not supply clinical risk estimates for venlafaxine. The neonatal FAERS analysis listed venlafaxine among maternal exposure drugs, but did not provide a venlafaxine-specific event rate.

Breastfeeding

LactMed reports that venlafaxine and active metabolite desvenlafaxine pass into breast milk and can be measured in infant blood. In one milk study of six mothers and seven infants, the combined estimated infant exposure was 6.4% of the maternal weight-adjusted dose; no adverse effects were reported in those infants (Ilett 2002). In another study, 13 mothers and their nursing infants provided milk and infant plasma samples; no adverse events were observed or reported (Newport 2009). These small studies cannot rule out uncommon effects. A 2025 physiologically based pharmacokinetic model estimated average relative infant daily exposure of 3.8% to 7.6% across simulated CYP genotypes; this was a model output, not an observed clinical outcome. LactMed says concurrent side effects have rarely been reported and recommends monitoring, especially for newborn or preterm infants, for excessive sleepiness and adequate weight gain. MotherToBaby reports that side effects in nursing children have sometimes been reported, including sleepiness, irritability, poor feeding, or trouble gaining weight. The Effexor XR label states: "Because of the potential for serious adverse reactions in nursing infants from Effexor XR, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother."

What was tested

Pregnancy evidence reviewed here includes observational cohort and case-control studies, a systematic review of cohort studies, and spontaneous adverse-event reports. The studies examined miscarriage, major and specific birth defects, preterm birth, gestational diabetes, preeclampsia, postpartum hemorrhage, and newborn adaptation. The FDA label says there are no adequate and well-controlled studies in pregnant women. Breastfeeding evidence includes small studies measuring venlafaxine and desvenlafaxine in milk and infant blood, plus reported infant outcomes. A 2025 maternal-fetal pharmacokinetic model used a limited pregnancy validation sample (seven maternal plasma samples and nine cord-blood samples); it modeled drug levels rather than clinical pregnancy outcomes. A separate 2025 lactation model used prior clinical data to estimate relative infant daily exposure; it modeled exposure rather than new clinical infant outcomes. A 2026 FAERS analysis described neonatal adverse-event reports but did not report a venlafaxine-specific event rate.