Amniotic Fluid Index and Preinatal Outcome in Postterm Pregnancy

Lee, Kyung Bok; Kim, Hyun Chan

Abstract

A pregnancy is considered postterm if it is beyond 294 days (42 complete weeks). Several investigators have demonstrated that postterm pregnancy may be accompanied by a rise in perinatal morbidity and/or mortality. Abnormalities such as meconium staining, cringenital anomalies, intrauterine growth retardation, postmaturity syndrome, fetal asphyxia have been reported in some cases of reduced amniotic fluid volume (oligohyramnios) which is commonly observed in postterm pregnancies. Amniotic fluid volume has been shown to decrease significantly as gestational age advances beyond term. Oligohydramnios has particular relevance to postterm pregnancies. Poor perinatal outcomes of oligohydramnios on postterm pregnancy have been reported by several authors. To date, however, the relationship between oligohydramnios in pastterm pregnancy and fetal outcome is debatable. The purpose of this clinical study was to evaluate the relationship between oligohydr- amnios and perinatal outcome in 64 cases of postterm pregnancies. Amniotic fluid index(AFI) values were measured semiweekly in 64 good dated, uncomplicated singleton pregnancies. AFI values were categorized into 2 groups. The group 1; patients whose final AFI value was above 5.0 cm; Group 2, patients whose AFI value fell below 5.0 cm. Adverse fetal outcome was defined by the presence of meconium staining, fetal heart rate decelerations, cesarean delivery for fetal distress, low Apgar score at 1 and 5 minutes, neonatal intensive care unit admission, and perinatal mortality. The fetal outcome was compared group 1 with group 2 and results obtained were as follows: 1. The incidence of oligohydramnios in postterm pregnancy was 54.7 %. The average diminution of amniotic fluid index was from 8.2 1.8 cm to 5.6+2.2 cm/week. 2. The incidence of meconium-staining in amniotic fluid was 40.6 % (Group 1: 20.7 %, Group 2: 57.1 %) and showed statistically significant difference between the two groups(p= 0.003). 3. The incidence of Apgar score less than 7 was 23.4% in 1 minute (Group 1: 13.8 %, Group 2: 31.4 %) and 4.7 % in 5 minutes(Group 1: 3.4%, Group 2: 5.7 %), respectively and showed no statistically significant difference between the two groups (p=0.140, p=1.000). 4. I'he incidence of cesarean delivery due to fetal distress was 12.5 % (Group 1: 6.9%, Group 2: 17.1 %) and showed no statistically significant difference between the two groups (p=0.275). 5. The incidence of admission to NICU was 12.5 % (Group 1: 6.9%, Group 2: 17.1 %) and showed no statistically significant difference between the two groups (p=0.275). Adverse fetal outcome was not uniformly observed in postterm pregnancies with oligohydramnios. Amniotic fluid index in oligohydramnios group as a single independent guide was not enough to predict fetal outcomes in postterm pregnancy without specific pathologic condition of fetus.