EARLY AMNIOTOMY INCREASES THE FREQUENCY OF FETAL HEART-RATE ABNORMALITIES

Objective To determine whether early amniotomy, when practised as an i solated intervention, increases the hourly rate of fetal heart rate re cord abnormalities. Design This is a secondary analysis of the results of a multicentre randomised trial of early vel sus late amniotomy in labour. Setting Secondary and tertiary level teaching hospitals. Inter vention Early amniotomy versus an attempt to conserve the amniotic mem branes. Main outcome measures The hourly rates of early, mild variable , severe variable and late decelerations; caesarean section rates. Res ults Severe variable decelerations, when classified as categorical eve nts (greater than or equal to 1/h to 2/h, greater than or equal to 2/h to < 4/h, greater than or equal to 4/h), were more frequent in the am niotomy group (chi(2) for trend = 5.7, P = 0.017). The mean hourly rat es of severe variable and late fetal heart rate decelerations were inc reased in the amniotomy group (severe variable: amniotomy group 1.4/h, control 0.7/h, P = 0.021; late: amniotomy group 3.3/h, control 2.3/h, P = 0.011). Although the overall rate of caesarean was similar in the two groups (OR 1.2; 95% CI 0.8-1.8), there was an increase in caesare an section for fetal distress (OR 2.3; 95% CI 1.1-4.5) associated with amniotomy. Conclusion Our data suggest that early amniotomy increases the hourly rate of severe variable fetal heart rate decelerations wit hout evidence of an adverse effect on neonatal outcome, In settings wh ere the diagnosis of fetal compromise is based primarily on electronic monitoring, caesarean section for fetal distress may be increased by early amniotomy.