Effect of maternal body mass index on in vitro response to tocolytics in term myometrium

Objective: We sought to investigate the effect of body mass index (BMI) on in vitro response to tocolytics. Study Design: Myometrial biopsies were obtained at the time of scheduled cesarean deliveries from term nonlaboring women with BMI ≤29.9 (26.3 ± 1.3; n = 7), 30-34.9 (31.8 ± 1.2; n = 16), and ≥35 (39.5 ± 4.9; n = 9). Tissue strips were suspended in organ chambers for isometric tension recording. The effects of cumulative doses (10^-10 to 10^-5 mol/L) of nifedipine or indomethacin on spontaneous uterine contractility were determined. Areas under the contraction curve were compared using 1-way analysis of variance with Tukey post hoc test. Results: Myometrial response to tocolytics did not differ between the BMI groups. Nifedipine, but not indomethacin, significantly inhibited myometrial contractility independent of BMI. Conclusion: BMI does not affect uterine response to tocolytics in isolated uterine tissue from term nonlaboring women.