Comparison of Amniotic Fluid Index at Different Gestational Age in Normal Pregnancy

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Sonographic assessment of amniotic fluid has formed an integral and important component of pregnancy assessment of fetal wellbeing. Changes in amniotic fluid volume are associated with variable outcome of the fetus. Amniotic fluid index which is an objective means of assessing adequacy of amniotic fluid volume does not only vary with gestational age but also differs from population to population. The study determined the reference values of amniotic fluid index and compared the values with the established ranges throughout gestation in uncomplicated singleton pregnancies among women attending our antenatal care facility. This was a longitudinal prospective assessment of amniotic fluid index in eighty six healthy pregnant women with singleton pregnancies recruited at 20 to 22 weeks of gestation and followed up to 41 weeks and 3 days. The patients recruited at 20 weeks had amniotic fluid measurements at recruitment and 4 weeks apart until 40 weeks gestation. Those recruited at 22 weeks had it also at recruitment and 4 weekly with the last estimation at 41 weeks +3 days. These measurements were plotted against their respective gestational ages. The graph was then analyzed using statistical and graphical packages of SPSS version 21. The study populations mean, 5th and 95th percentiles was documented and discussed appropriately. A total of 414 readings were obtained from 81 subjects who underwent more than 3 measurements. Analysis of the data obtained shows a rising AFI with a mean 28 weeks and, thereafter gradually fell till term. The mean age obtained in the study group compared with that of Caucasians showed statistically significant difference (P=0.014). Also, comparison with Chama et al. showed obvious statistical difference at the lower limit (5th percentile; P=0.007, 50th percentile; P=0.006) but no differences at the upper limit (95th percentile; P=0.726). Amniotic fluid index values appear to be differing in different population. The reference range of AFI used in clinical practice should therefore be based on data obtained from local population.