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
