Maternal parity and functional contractility of human myometrium in vitro in the third trimester of pregnancy

Objective It is well established that the duration of the first and second stages of labor are shorter in parous women than in their nulliparous counterparts, a phenomenon not well understood. The aim was to examine the effect of maternal parity on contractile parameters of human myometrium. Design Myometrial strips were excised from n = 74 women at cesarean delivery and recordings of contractile activity analyzed and compared across three clinical groups: 1. No previous delivery (P0); 2. One previous delivery (P1); 3. Greater than one previous delivery (P>1). Results There was a trend towards greater mean contractile force in the P>1 group than the P1 and P0 groups (P= 0.412). Frequency of contractions was less in the P1 group than in the P0 and P>1 groups(P = 0.027). No differences were observed in relation to all other parameters. Conclusion Excluding frequency, no intrinsic differences were observed in the functional parameters of human uterine contractions in relation to parity.