Is grand multiparity an independent predictor of pregnancy risk? A retrospective observational study.

OBJECTIVE To determine whether high maternal parity has any effect on pregnancy outcome independent of other maternal characteristics. DESIGN AND SETTING Retrospective observational study using the database of a referral obstetric unit in a 280-bed regional hospital in far north Queensland. PARTICIPANTS All 15 908 women who had singleton births between 1992 and 2001, comprising 653 women with grand multiparity (>or= 5 previous births at gestation >or= 20 weeks) and 15 255 women with lower parity. MAIN OUTCOME MEASURES Spontaneous vaginal birth, postpartum haemorrhage (estimated blood loss > 500 mL), placental retention requiring manual removal, blood transfusion associated with the birth, and perinatal death. RESULTS Women with grand multiparity were significantly older than those with lower parity, more likely to be Indigenous, not to have had antenatal care, to have smoked during pregnancy and to have had one or more previous caesarean sections. On univariate analysis, women with grand multiparity were more likely to have a postpartum haemorrhage (9.2% v 5.3%) and blood transfusion (2.8% v 1.5%). However, multivariate logistic regression analysis of women who began labour (ie, did not have an elective caesarean section) showed that grand multiparity was not significantly associated with postpartum haemorrhage or blood transfusion when other maternal characteristics were included in the model (regression coefficients [95% CI], 1.36 [0.99-1.87] and 1.09 [0.59-2.02], respectively). However, they remained more likely to have a spontaneous vaginal birth (regression coefficient [95% CI], 2.10 [1.56-2.74]). CONCLUSIONS Women with grand multiparity do not have an increased likelihood of poor pregnancy outcomes. Birth-suite protocols which dictate extra interventions as routine during labour in these women should be revised.