Gender, gestation, and birthweight-based differences in the timing of passage of first urine and meconium in neonates: A prospective observational study.

Introduction: The cut-off for referral to a higher center and further investigations for the delayed passage of first urine and meconium by a neonate have been traditionally kept after 48 hours of birth. There are very few studies regarding this in Indian neonates, and previous studies have relied primarily on the mother's recall of the event which may have led to recall bias. Therefore, through this study, we wanted to use hospital intake/output records to identify the risk factors that affect the timing of passage of first urine and stool in neonates delivered at our center and to find out if the cut-off of 48 hours to call it a delay is justifiable.

Methodology: This was a single-center, prospective observational study conducted in Eastern India. After obtaining ethics committee approval, the eligible neonates delivered at the center were prospectively enrolled between June 2020 to December 2022. The timing of passage of first urine and meconium was noted using 3 hourly collected information from the input/output charts maintained by the nursing staff in the postnatal wards. The median time of passage of first urine and meconium was compared across gender, gestation, and birth weight. To find the factors associated independently with delayed passage of meconium, multivariable logistic regression was used.

Result: A total of 330 neonates were enrolled prospectively in the study. Approximately two-thirds of them passed first urine (69.7%) and meconium (62.7%) within 6 hours after delivery. The median and interquartile range (IQR) of the time of passage of the first urine was 4 (1-7) hours of life. This did not vary significantly for gender, gestation, and birthweight categories. The median (IQR) of time of passage of meconium was 4 (1-8) hours of life, which was significantly higher for male [5 (2-8.5), ( = 0.029)] and preterm neonates [6.3 (2.5-12), ( = 0.001)], but did not vary significantly for birthweight categories. On multivariable logistic regression, twin gestation [OR 4.15 (95% CI 1.09-15.76); = 0.036] and preterm birth [OR 2.97 (95% CI 1.18-7.43); = 0.02] increased the odds of passage of meconium beyond 12 hours' postnatal age. 99.39% and 98.77% of the neonates passed urine and meconium respectively within 24 hours.

Conclusion: The median time of passage of first urine was not influenced by gender, gestation at birth, and birthweight categories. The median time of passage of meconium was significantly higher for male and preterm neonates. Also, with early initiation of direct breastfeeding and good feeding support most neonates pass their first urine and stool by 24 hours of life. So, maybe it's time to revise the cut-off for referrals or investigations from 48 hours to 24 hours of life. However, further studies with larger sample sizes will be required to confirm this cut-off.