Association Between Immediate Pre-delivery Ultrasound Estimated Fetal Weight and Labour Outcomes Among Term Parturients at Kenyatta National Hospitalin 2020-202 – (a Prospective Cohort Study)

Abstract

Introduction: Fetal weight, especially macrosomia, is associated with adverse obstetric outcomes including prolonged labor, operative delivery and shoulder dystocia. Studies from high income countries suggest that ultrasound estimated fetal weight (UEFW) of more than 90th percentile for gestational age is associated with postpartum hemorrhage, genital tract injuries, poor progress of labor, Caesarian section, instrumental delivery, shoulder dystocia and birth asphyxia. UEFW within one week of delivery correlates with actual birth weight. It is unknown if these study findings may apply in low-income settings due to differences in pelvic types and sizes, birth weights and prevalence of cephalopelvic disproportion (CPD). In this study, we sought to determine the association between UEFW close to delivery, which correlates with actual birth weight, and labor outcomes among term parturients at Kenyatta National Hospital (KNH). Objective: To compare adverse labor outcomes between term parturients with immediate antepartum UEFW≥ 90th versus <90th percentile for gestational age at KNH in 2020-21. Methodology: This was a prospective cohort study in which term women delivering at KNH were screened and those eligible enrolled, half with an UEFW ≥ 90th percentile (n=62) and another half with UEFW <90th percentile (n= 62) for gestational age based on ultrasound performed within the last one week of pre-delivery period. Participantswerefollowed up to describe the labour (maternal and foetal) outcomes. Data was collected and uploaded into the SPSS version 23 software for cleaning and analysis. Sociodemographic characteristics of the two exposure groups were compared. Categorical variables were summarized as frequencies and proportions and compared using Chi-square test while continuous variables were summarized as means and standard deviations or median and interquartile range and compared using student t test or Mann Whitney U test as appropriate. The relative risk and adjusted relative risk and 95% confidence interval associated with labour (maternal and foetal) outcomes were estimated using generalized linear regression model with Poisson distribution adjusting for potential confounders including age, gestational age, parity, and cervical dilatation as appropriate. P value < 0.05 was considered statistically significant. Results: Between October 2020 and April 2021, 137 potential participants were screened and 124 were found to be eligible, 62in each group. The baseline sociodemographic and obstetric characteristics were comparable between the two groups. However, the mean UEFW was higher 11 among those with UEFW ≥90th percentile (3917.6g) compared to those with UEFW <90th percentile (3247.2g) for gestational age (P<0.05). More women with UEFW≥90th percentile (45.2%), underwent emergency caesarean section (CS)and operative vaginal delivery compared to those with UEFW<90th percentile (24.2%) for gestation age (P= 0.010). In adjusted analysis, the risk of emergency CS and operative vaginal delivery was 1.6(95% CI) times greater in the UEFW≥90th percentile versus the UEFW <90th percentile for gestational age group. There was higher but not statistically significant risk of adverse maternal outcomes and neonatal outcomes in the UEFW≥90th percentile versus the UEFW <90th percentile for gestational age group. Conclusion: UEFW≥90thpercentile for gestational age done within the last week of pre-delivery period is associated with 1.6time greater risk of caesarian and operative vaginal deliveries and greater but not statistically significant risk of adverse maternal and fetal outcomes compared to UEFW<90thpercentile. Recommendations: Women with UEFW≥90thpercentile for gestational age within the last week of delivery should be counselled appropriately and monitored closely on the risk of CS and operative vaginal delivery. There is a need to conduct larger multicenter longitudinal studies powered to address not only mode of delivery but other adverse maternal and neonatal outcomes. Key Words: Estimated Fetal Weight, Pre-delivery Ultrasound, Labor, Maternal, Neonatal, outcomes.