Urinary output during induced labour in normotensive women: a prospective pilot study.

All fluid intake and urine output were monitored and measured in 103 consecutive women with normal blood pressure and without a history of pre-existing renal disease during induced labour for various indications. Epidural analgesia was administered in all these women and labour was augmented with oxytocin infusion. All urine specimens passed were tested for specific gravity. The temperature of the labour rooms was between 25 and 27 degrees C. Analysed results (from 50 women) shows that at a mean fluid intake of 75 ml/hour (standard deviation (SD) 21.84), oliguria (urine output <30 ml/hour) occurred in 42 (84%) of the women. There was a positive correlation between fluid intake and urinary output (r(2)=0.8515, P<0.0001). Urinary specific gravity was high (>1010) in all the specimens throughout the study. This study suggests that oliguria may be a common component of labour managed in this manner and its interpretation in pre-eclamptics in labour may be viewed in this context. Oliguria may therefore be a poor indicator of renal function or worsening pre-eclampsia during labour and its management needs to be limited to the severe and persistent variety to avoid renal complications. We believe from this study that relevant urine and blood biochemistry are better correlates of renal function in labour.