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. Key words: indomethacin, nifedipine, obesity, organ chamber, oxytocin, uterine contractility