Lithium use during pregnancy ups risk of preterm birth

Pregnant women who are using lithium are at increased risk of spontaneous preterm birth, according to a retrospective study.

Researchers looked at 867,454 births during a 10-year period in Victoria, Australia. They determined the incidence of spontaneous preterm birth (<37 weeks of gestation), large for gestational age (LGA) (birthweight >90th percentile), macrosomia (birthweight >4,000 g), major congenital malformations, and congenital cardiac malformations in relation to lithium exposure during pregnancy.

Of the women, 234 (0.03 percent) were exposed to lithium during pregnancy. Compared with nonexposure, lithium exposure was associated increased risks of spontaneous preterm birth (8.1 percent vs 2.4 percent; adjusted relative risk [aRR], 2.18, 95 percent confidence interval [CI], 1.45–3.30), an LGA infant (13.7 percent vs 6.4 percent; aRR, 1.94, 95 percent CI, 1.36–2.76), and congenital cardiac malformations (3 percent vs 0.8 percent; aRR, 2.64, 95 percent CI, 1.26–5.53).

Lithium exposure had a null effect on the risk of major congenital malformations overall (aRR, 1.51, 95 percent CI, 0.92–2.50).

Analyses restricted to women with bipolar disorder or schizophrenia diagnoses yielded similar results. Lithium exposure remained associated with increased risks of spontaneous preterm birth (aRR, 1.88, 95 percent CI, 1.06–3.32) and birth of an LGA infant (aRR, 1.68, 95 percent CI 1.07–2.65).

The findings provide evidence that may guide shared decision-making around lithium use during pregnancy.