Extended longitudinal study of uterine activity among low-risk women.

Abstract

Eighty-nine black women without major medical risks for preterm labor participated in this longitudinal, prospective study for the evaluation of usual prelabor uterine activity and for the assessment of how gestational age, time of day, maternal weight, age, and parity affected contraction frequency. Participants wore an ambulatory tocodynamometer for 72 consecutive hours at three points in gestation during the second and early third trimesters while engaged in usual home and work activity. Data obtained from the 81 women with uncomplicated term pregnancies demonstrated a significant increase in contraction frequency with advancing gestational age between 22 and 33 weeks. After 26 weeks, significantly more uterine activity occurred at night. Perhaps because of detection difficulties, contraction frequency was inversely related to maternal weight in women weighing greater than 112% ideal weight. Maternal age and parity did not affect contraction frequency. Contraction characteristics of eight women experiencing preterm labor or medically indicated preterm delivery are described.