Background Adverse drug reactions (ADR's) could be expected more frequently in pregnant women. This study was performed in order to identify ADR's to tocolytic drugs in hospitalised pregnant women.

      Methods
      A prospective cohort study was performed in two General Hospitals of the Instituto Mexicano del Seguro Social (IMSS) in Mexico City. Two hundred and seven women undergoing labor, premature labor, threatened abortion or suffering any obstetric related disease were included. Drug prescription and signs and symptoms of any potential ADR were registered daily during the hospital stay. Any potential ADR to tocolytic drugs was evaluated and classified by three of the authors using the Kramer's algorithm.


      Results
      Of the 207 patients, an ADR was positively classified in 25 cases (12.1%, CI95% 8.1 to 17.5%). All ADR's were classified as minor reactions. Grouping patients with diagnosis of threatened abortion, premature labor or under labor (n= 114), 24 ADR's were related to terbutaline, accounting for a rate of 21.1 ADR's per 100 obstetric patients. Obstetric patients suffering an ADR were older than obstetric patients without any ADR. However, the former received less drugs/day × patient-1 and had a shorter hospital stay (p < 0.05) whereas the dose of terbutaline was similar between the two groups. Terbutaline inhibited uterine motility in women with and without any ADR at a similar rate, 70 and 76% respectively (x2 = 0.07; p = 0.8).


      Conclusion
      Terbutaline, used as a tocolytic drug, was related to a high frequency of minor ADRs and to a high rate of effcicacy.