For a study, researchers sought to determine if tramadol exposure during early pregnancy was linked to an increased risk of spontaneous abortion or serious congenital abnormalities. The research was a countrywide cohort study that included all registered pregnancies between January 1, 1997, and December 31, 2016. The National Prescription Register was utilized to determine maternal tramadol exposure. Using propensity scoring, pregnancies with maternal tramadol exposure were matched with pregnancies without maternal tramadol exposure in a ratio of up to 1:4. Spontaneous abortion and significant congenital abnormalities were the leading outcomes. The hazard ratios (HRs) of spontaneous abortion were estimated using Cox proportional hazards regression, and the relative risk ratios (RRs) of significant congenital abnormalities were estimated using log-binomial models.

The studies of spontaneous abortion and serious congenital abnormalities comprised 36,467 (tramadol exposure n=7,310) and 18,907 (tramadol exposure n=3,796) pregnancies, respectively. Spontaneous abortion occurred in 893 (12.2%) of fetuses with maternal tramadol exposure and 3,471 (11.9%) of pregnancies without maternal tramadol exposure (HR 1.06, 95% CI 0.99–1.14). A serious congenital deformity occurred in 151 (4.0%) of fetuses with maternal tramadol exposure, compared to 579 (3.8 %) of pregnancies without maternal tramadol exposure (RR 1.04, 95 % CI 0.87–1.24). Tramadol exposure during early pregnancy did not appear to enhance the incidence of spontaneous abortion or significant congenital abnormalities.