Role of Amniotic Fluid Index in Prediction of Fetal Distress During Labor in Uncomplicated Pregnancies at 40 Weeks and Beyond

Abstract

An indirect estimate of the amount of amniotic fluid has long been included in all protocols of ultrasound findings as an indirect characteristic of the fetus. A decrease in the amount of amniotic fluid in periods of more than 40 weeks of pregnancy in the absence of an earlier detected pathology on the part of the fetus and mother is presumably a sign of worsening uteroplacental blood flow. This concept was proposed by some studies of dopplerometry of the renal arteries in fetuses with a reduced amount of amniotic fluid [1,2]. Other studies have not confirmed this fact, suggesting that the cause of oligohydramnios is rather a reduced fetal weight than redistribution of its blood flow [3]. Traditionally, oligohydramnios is associated with a high risk for the fetus in childbirth [4,5]. This may be the result of compression of the umbilical cord or potential placental insufficiency. There are many publications on the association of poor perinatal outcome and oligohydramnios [6-8]. Chauhan et al, [6] in a meta-analysis of 18 studies involving 10 551 patients, demonstrated that antenatal and intrapartum values of the amniotic index less than 5 cm were associated with a significant risk of caesarean section or fetal distress and low Apgar scores at 5 minutes [6]. Unfortunately, this review, like many other similar publications relating to the association of oligohydramnios and perinatal outcomes, is not randomized and not coordinated according to the control groups of patients, inclusion groups, which can distort the overall picture. And only one of the above studies includes a randomized study of the amniotic index in women in labor [7]. It is logical to assume that these data can be extrapolated to similar situations in nulliparous women. Similarly, Casey et al. [8]. conducted a retrospective study of 6423 patients with a gestational age of more than 34 weeks and an amniotic index of 5 cm. Low water was detected in 2.3% of cases and in most cases is associated with induction of labor, stillbirth, aspiration of meconium and neonatal mortality. There are studies with polar opposite results. Magann et al, [9] found that AI is a poor prognostic test for identifying pregnant women at risk for adverse perinatal outcomes. Rainford et al, [10] indicate a lack of correlation between AI indicators and the level of operational activity due to fetal distress, the number of newborns in need of mechanical ventilation of the newborn, and low Apgar scores. A study by Conway et al, [11] hypothesizes that isolated oligohydramnios during normal pregnancy is not associated with a decrease in the compensatory abilities of the fetus. The pathogenesis of oligohydramnios during pregnancy over 40 weeks, as well as the relationship of this indicator with the outcome of childbirth, is not well understood. What is the Abstract