MATERNAL AND PERINATAL OUTCOMES IN BORDERLINE OLIGOHYDROMNIOS IN A TERTIARY CARE CENTRE: AN OBSERVATIONAL PROSPECTIVE STUDY

Abstract

Introduction

Amniotic fluid is the protective fluid contained in the amniotic sac in a gravid uterus. This fluid acts as a cushion for the growing fetus and facilitates the exchange of water, nutrients and biochemical products between the mother and the fetus. Amniotic fluid is the ultrafiltrate of maternal plasma. It  passes through the fetal membrane through osmotic and hydrostatic forces. Fetal kidneys become functional at approximately 16 weeks, fetal urine also contributes to the fluid. Although amniotic fluid is mainly removed by the fetal swallowing, some amount of fluid is absorbed by the fetal skin as well.

Amniotic fluid volume is also related to gestational age. Amniotic fluid measures approximately around 50 mL at 12 weeks, 400 mL at 20 weeks, and reaches almost 1 L at 36-38 weeks. Thereafter, the volume reduces to 600-800 mL at term gestation. It further decreases to approximately 200 mL beyond 42 weeks [1]. The fluid acts as  shock absorber and protects the fetus from extraneous injuries. Additionally, it allows growth of the fetus and its free movement. Amniotic fluid guards against umbilical cord compression. Its  aseptic and bactericidal action protects the fetus and prevent infection in the uterine cavity [1]. Amniotic fluid is an indicator of  the placental function and is used for assessing fetal well-being. Amniotic fluid index (AFI) is calculated by adding the depth in centimeters of the largest vertical pocket in each of the four equal uterine quadrants. Normal AFI ranges between 8.1 and 25 cm. AFI of ≤5 cm is defined as severe oligohydramnios. Borderline oligohydramnios (BO) is defined as AFI of 5.1-8 cm [2].

According to some studies, borderline AFI increases the risk for cesarean section because of fetal distress and increases the incidence of low Apgar score, low birth weight (LBW), respiratory distress and increased need for neonatal intensive care unit (NICU) admission [2-4]. However, Luo et al. did not find any such correlation in terms of fetal distress or neonatal mortality. Even though the incidence of cesarean delivery in unfavourable cervical ripening was not assessed for every patient, it was determined according to the cervical condition of the patient; hence, it was not assessed in the study.[5]  In their study, Choi et al. did not find any correlation between borderline AFI and fetal outcomes [6]. Despite several studies, the prediction of adverse pregnancy outcomes in the presence of borderline AFI is not definite and hence prenatal surveillance is not recommended in borderline AFI [2]. We aimed to investigate the maternal and perinatal outcomes in borderline AFI.