The relationship between oligohydramnios and the onset of preterm labor inpreterm premature rupture of membranes

OBJECTIVE: The objective of this study was to determine whether a reduced a mniotic fluid volume was associated with the onset of preterm parturition i n patients with preterm premature rupture of membranes. STUDY DESIGN: An amniotic fluid index was determined before transabdominal amniocentesis in 129 patients with preterm premature rupture of membranes ( gestational age less than or equal to 35 weeks). Amniotic fluid was culture d for aerobic and anaerobic bacteria, as well as for mycoplasmas, Survival techniques were used for analysis. RESULTS: Amniotic fluid index was less than or equal to5 cm in 29% of patie nts (38/129). Patients with an amniotic fluid index of less than or equal t o5 cm had a significantly higher rate of positive amniotic fluid culture th an those with an amniotic fluid index of >5 cm (42% [16/38] vs 18% [16/91]; P < .01;). Spontaneous preterm delivery within 24 hours and 48 hours was m ore frequent among patients with an amniotic fluid index of <less than or e qual to>5 cm than those with an amniotic fluid index of >5 cm (for 24 hours , 29% vs 12%; for 48 hours. 42% vs 21%; P < .05 for each). The amniocentesi s-to-delivery interval was significantly shorter in patients with an amniot ic fluid index of <less than or equal to>5 cm than in patients with an amni otic fluid index of >5 cm (median, 38 hours; range, 0.2-1310 hours; vs medi an, 100 hours; range 0.1-2917 hours; P < .01;). Moreover, Cox proportional hazards model analysis indicated that an amniotic fluid index of <less than or equal to>5 cm was a significant predictor of the duration of the pregna ncy after adjustment for gestational age and the results of amniotic fluid culture (odds ratio, 2.4; 95% confidence interval, 1.4-3.9; P< .001;). CONCLUSION: Patients with preterm premature rupture of membranes and an amn iotic fluid index of <less than or equal to>5 cm are at increased risk for a shorter interval to delivery.