Use of tramadol in early pregnancy and congenital malformation risk.

Only few studies exist regarding the risk of a teratogenic effect of tramadol when used in early pregnancy. Using the Swedish Medical Birth Register, women (deliveries in 1997-2013) who had reported the use of tramadol in early pregnancy were identified. Maternal characteristics and concomitant drug use were analyzed. Among 1 682 846 women (1 797 678 infants), 1751 (1776 infants) had used tramadol, 96 of the infants had a congenital malformation and 70 of them were relatively severe. The adjusted odds ratio for a relatively severe malformation was 1.33 (95% CI 1.05-1.70). The odds ratios for cardiovascular defects (1.56, 95% CI 1.04-2.29) and for pes equinovarus (3.63, 95% CI 1.61-6.89) were significantly increased. The study suggests a teratogenic effect of tramadol but the risk increase is moderate.