A Clinical Study on Maternal and Perinatal Outcome of Oligohydramnios

Background : Oligohydramnios is one of the pregnancy associated common complications facing by obstetrician which is associated with adverse maternal and perinatal outcome such as birth defects, miscarriage, intrauterine growth restriction, still birth, preterm birth, increased operative interference etc. Objective: To assess the impact of oligohydramnios on maternal and perinatal outcome. Methods: This cross-sectional descriptive study was conducted at Department of Obstetrics and Gynecology, BSMMU, Dhaka from October 2017 to March 2018.Total 50 patients were enrolled by purposive sampling method according to the inclusion and exclusion criteria. Clinical evidence of oligohydramnios was looked for & confirmed by ultrasonography (USG). Based on Amniotic fluid index (AFI)measurements patients were divided into two groups. Those who have AFI <5cm and 5-8cm. The significance of difference or comparison of means was measured by Chi square test. Maternal and perinatal outcome in pregnancies with oligohydramnios were compared with those with 5-8cm amniotic fluid volume. Results: The mean age of the study population was 23.3±4.06 years and majority of the cases were multipara (56%) and presented at term (58%). Borderline oligohydramnios (AFI 5-8cm) was found in 74% cases and severe oligohydramnios (AFI <5cm) were found in 26% cases. Most common etiological factor was idiopathic. Fifteen cases (30%) had vaginal delivery and caesarean section rate 70%, no maternal mortality occurred in this study, perinatal mortality rate was 10%, low birth weight baby was 63.6% and NICU admission rate was 53.8%. Conclusion: An antepartum or intrapartum oligohydramnios is associated with significantly increased incidence of caesarean section for fetal distress and increased incidence of low-birth-weight babies and increased rate of neonatal complications.


Introduction
Oligohydramnios or reduced volume of amniotic fluid, particularly when it is diagnosed before term, is a great challenge to the obstetrician with regards to perinatal outcome. Although oligohydramnios is more common in third trimester, it can develop in any trimester. One to five percent of term pregnancies are complicated by this. 1 The normal index of amniotic fluid (AFI) ranges from 8.1-20 cm. Oligohydramnios is defined as AFI less than 5 cm or 10th percentile for the gestational age or AFI less than or equal to 5 cm regardless of gestational age. AFI between 5.1-8 cm is known as Borderline Oligohydramnios. 2 To allow normal fetal movement and growth and to cushion the fetus and umbilical cord, an adequate volume of amniotic fluid is necessary. Oligohydramnios inhibits these processes, especially when extreme, it can lead to fetal deformity, compression of the umbilical cord and death. The amount of amniotic fluid tends to be determined by a combination between fetal urine inflows and fetal swallowing outflows and intra-membranous water flow. 3,4 For the first two trimesters, the amniotic fluid accumulates and reaches a peak volume at 33 to 34 weeks. 5  performed by ultrasound measurement of the amniotic fluid compartment. A recent meta-analysis has shown that AFI <5 cm is associated with a substantial 2-fold increase in cesarean delivery rate for fetal distress and a 5-fold increase in APGAR score at 5 min below 7. 5 In our country Obstetricians often faces a situation in which pregnant women is noted to have oligohydramnios both clinically and sonographycally which is a predictor of adverse pregnancy outcome. But still limited number of proven studies about the perinatal outcome in patients with oligohydramnios is available here.

Diagnosis of Oligohydramnios is normally
Therefore, this research was conducted to assess the impact of oligohydramnios on maternal and perinatal outcomes.

Materials and Methods
From October 2017 to March 2018 this cross-sectional descriptive study was conducted at Bangabandhu Sheikh Mujib Medical University (BSMMU). Fifty patients who had oligohydramnios between 28 and 42 weeks of pregnancy participated in this study.
Inclusion criteria : 1. All cases admitted with oligohydramnios during the study period, 2. Age group between 18-40 years, 3. Pregnant women with gestational age between 28 to 42 weeks, 4. Singleton pregnancy.
After selection of cases, detailed history was taken, and physical examination was done. Clinical evidence of oligohydramnios was looked for and confirmed by ultrasound examination. AFI was evaluated in these patients with technique of Phelan et al. 2 An AFI <5 cm considered as oligohydramnios and 5.1-8 cm considered borderline AFI. Fetal clinical outcome measured with APGAR score. Total scoreis 10, normal= 7-10, mild perinatal asphyxia= 4-6, severe perinatal asphyxia =0-3. In case of mild to severe perinatal asphyxia, baby must be transferred to neonatal unit rapidly for further management. 6 Previously selected maternal outcome variables during these pregnancies were recorded on pretested proformas. Perinatal outcomes which was occurred in these neonates also recorded.
All data were converted to tabulated forms to obtain statistical information by Using Microsoft Excel and SPSS 17 program. Mean values of different parameters were compared to see the differences between two groups by using Student's unpaired 't' test. Chi-square test was performed to find the statistical difference regarding gravida distribution between groups. For all statistical analysis, 'p' value <0.05 was considered as significant.

Fig-1: Maternal outcome in caesarean section (n=35)
In this study the fetal outcome of 48 cases taking APGAR score at 1 minute and 5 minutes, the score of <7 at 1 minute was found in 37.5% (18) of cases and the score of <7 at 5 minutes was found in 41.7% (20) of cases. There were 2 cases of fresh still birth in this study (Fig 2)

Fig 2 : distribution of study population according to APGAR score (n=48)
In our study we found that 53.8% (7) cases with AFI <5cm and 35.1% (13) cases with AFI 5-8cm were admitted to NICU which was statistically significant (p<0.05) between two groups (Table V)  In this study we found that Respiratory distress, Meconium aspiration and healthy baby was statistically significant (p<0.05) between two groups (Table VI)

Discussion
During pregnancy, the amniotic fluid that covers the fetus plays many functions. It creates physical space for musculoskeletal growth, promotes normal fetal lung development, and helps to prevent umbilical cord compression. 7 Ultrasonography is the best way to detect oligohydramnios early, as well as other related conditions.
In this current study it was observed that women with AFI<5 cm was about 26% and 5-7 cm in 74% of cases. We also found that 29 cases (58%) out of 50 were diagnosed as oligohydramnios at term between 38-40 weeks of gestation and 21 cases(42%) were diagnosed < 37 weeks of gestation. Melamed

Conclusion
Now a day's oligohydramnios poses a challenge in obstetric management particularly when diagnosed before term. Although cause of oligohydramnios is unknown in most cases, amniotic fluid volume is a predictor of fetal tolerance of stress in labour. Reduced amniotic fluid volume is frequently associated with Preeclampsia, Intrauterine growth restriction, increased operative interference for fetal distress in labour. Low APGAR score at birth, perinatal death, still birth and higher NICU admission rate are higher in severe oligohydramnios cases.

Limitations of the study
The access to tertiary level hospital is low in case of all women of different socioeconomic status especially for poor even with high risks. Therefore, sample size is relatively small, and duration is short in this study.