Perinatal Outcome and Congenital Anomalies in Polyhydramnios –A Prospective Study

Background: The amniotic fluid that envelops the fetus acts as a protective shroud. Fetal well-being is reflected by the 
amniotic fluid index. When the amniotic fluid index exceeds 25cms, it is called polyhydramnios and is associated with 
increased incidence of congenital malformations and perinatal mortality. 
Objectives: To estimate the incidence of congenital malformations and to study the perinatal outcome in 
polyhydramnios. 
Study Design: Prospective study. 
Setting: Neonatal intensive care unit and the maternity wards of Father Muller Medical College Hospital, Mangalore. 
Study period was 2 years. 
Methods: Amniotic fluid index was measured by ultrasound, 29 cases of polyhydramnios identified were evaluated and 
followed up. Congenital malformations were observed both by ante natal and post natal ultrasounds, other relevant 
investigations were also done when necessary. The perinatal outcome in terms of congenital anomalies, fetal distress and 
mortality were recorded. 
Results: 29 cases of Polyhdramnios were detected. Congenital malformations were identified in seven neonates 
(24.1%). Diaphragmatic hernia and hydrops fetalis were the most common congenital malformations observed. Nine 
neonatal deaths were documented (31%). Six cases of fetal distress were observed (19%). Incidence of congenital 
malformations and mortality increased significantly when the amniotic fluid index was above 30cms. 
Conclusion: There was a significant risk of congenital malformations, neonatal mortality and fetal distress in 
polyhydramnios, these risks rose exponentially with a further rise in amniotic fluid index over 30cms.


Introduction
Amniotic fluid or liquor amnii is the protective liquid contained by the amniotic sac during pregnancy. Amniotic fluid protects the fetus by a cushioning effect in the mother's abdomen, it allows for easier fetal movement and promotes skeletal development, it provides a barrier against infection, it also aids in the development of the lungs and formation of urine and meconium. Polyhydramnios is defined as amniotic fluid index more than 25 cm. 1 The incidence of polyhydramnios ranges from 0.5-1.5% of all pregnancies. 2,3 Congenital malformations are more likely in polyhydramnios and these malformations may occur in almost every organ system. But, commonly these malformations are associated with systems that involve absorption of fluids and swallowing in the fetus. 4,5 Anencephaly, duodenal or esophageal atresia and renal agenesis are the more frequent anomalies. In terms of amniotic fluid index, the more severe the polyhydramnios, greater is the incidence of congenital anomalies and poor perinatal outcome. The purpose of this study was to estimate the incidence of congenital malformations and to study the perinatal outcome in polyhydramnios.

Materials and Methods
This prospective study was conducted in the neonatal intensive care unit and the maternity wards of Father Muller medical college hospital, Mangalore. The study period was 2 years, 29 newborns were included in this study. Ultrasonography was used to quantitate the amniotic fluid index and confirm polyhydramnios. Following a detailed history and clinical examination, postnatal ultrasound, x rays, CT scans were obtained if the clinical situation warranted it. Chi square test, Gaussian test and Fischer's exact test were used to calculate the statistical significance of the data obtained.

Methodology
The Amniotic fluid index was assessed by placing the patient supine, the uterus was viewed as four equal quadrants. The ultrasound was transduced perpendicular to the plane of the floor and aligned longitudinally with the patients' spine, vertical depth of the largest amniotic fluid pocket was measured and the amniotic fluid index was calculated from the sum of four quadrant pocket depths. Congenital anomalies were identified by an antenatal ultrasound and recorded, if required other investigations were done post natal. The outcome was determined by following up the newborn in the neonatal period.

Results
During the study period of two years, there were 29 cases of polyhydramnios; congenital malformations were observed in 7 cases (24.1%). The new born mortality was 9 (31%).
In our study the congenital malformations observed were 2 cases each of diaphragmatic hernia and hydrops fetalis, one case each of micrognathia, duodenal atresia and anencephaly were also observed.
Six newborns (19%) had fetal distress. The mode of delivery was Caesarean in 9 (31%). When the total number of cases, were further classified on the basis of the amniotic fluid index as more than 30cms (12 cases) and between 25-30cms (17 cases), the corresponding incidence of congenital malformations was 50% and 5.9% and the corresponding mortality was 50% and 17.6%.
In the study conducted by Desmedt Els, 4 twenty percent of the congenital anomalies were not detected by an antenatal ultrasound, whereas in our study all seven congenital anomalies were detected by an antenatal ultrasound. There were 11 preterm deliveries (37%) in our study but only 7.7% preterm births in the study conducted by Shabnam. 10 Fetal distress was observed in 6 deliveries (20.6%) in our study compared to only 4.1% in the study conducted by Baron. 15 The mode of delivery was caesarean in nine newborns (31%) in our study and was similar to the 27.9% observed in the study by Shabnam. 10 The perinatal mortality was a high 31% in our study, which was significantly higher than the perinatal mortality observed in the studies by Stoll 5 (4.3%), Desmedt Els 4 (4.9%) and Lyndon M Hill 8 (7%).

Conclusion
It is very important to recognize polyhydramnios, because of its frequent association with fetal malformations and perinatal mortality. Antenatal ultrasound is an accurate tool to identify congenital anomalies. In severe polyhydramnios when the amniotic fluid index exceeded 30, the incidence of both congenital malformations and perinatal mortality was a significantly high 50%. The risk of fetal distress is also significant. The perinatal outcome may be influenced by frequent assessment of the amniotic fluid index and regular follow up of the identified cases of polyhydramnios.