Amniotic fluid is an essential component of the intrauterine environment, providing mechanical protection, facilitating fetal movement, preventing umbilical cord compression, and contributing to fetal lung and musculoskeletal development. It also possesses antibacterial properties and serves as a medium for nutrient exchange between the fetus and the maternal circulation. Any deviation in amniotic fluid volume can significantly compromise fetal well-being and pregnancy outcomes.¹ The amniotic fluid index (AFI) is a standardized ultrasonographic method used to assess amniotic fluid volume, particularly after 24 weeks of gestation. AFI is calculated by summing the deepest vertical pockets of fluid measured in four uterine quadrants. Normal AFI ranges from 5 to 25 cm. Values below 5 cm indicate oligohydramnios, while values above 25 cm indicate polyhydramnios.²,³ Oligohydramnios is commonly associated with placental insufficiency, fetal growth restriction, fetal distress, and increased operative delivery rates. Reduced fetal urine output secondary to chronic hypoxia is considered a key pathophysiological mechanism. Polyhydramnios, on the other hand, may result from impaired fetal swallowing, maternal diabetes, or idiopathic causes and is associated with preterm labor, malpresentations, cord prolapse, and neonatal metabolic complications.⁴,⁵ Although AFI measurement is routinely performed during antenatal surveillance, its predictive value for immediate neonatal outcomes such as birth weight, APGAR scores, respiratory distress, and NICU admission remains inconsistently reported across studies. This highlights the need for population-specific evidence to guide obstetric decision-making. NEED FOR THE STUDY Despite routine AFI monitoring during antenatal care, the relationship between abnormal AFI and immediate neonatal outcomes remains inadequately characterized in many Indian populations. Understanding this association is vital for early risk stratification, timely obstetric intervention, and neonatal preparedness. This study aims to bridge this gap by evaluating the correlation between AFI status and composite fetomaternal outcomes in a tertiary care setting in Kerala.

Study Design This study was conducted as a prospective observational study designed to evaluate the association between amniotic fluid index (AFI) and fetomaternal outcomes in late pregnancy. Study Setting The study was carried out in the Department of Obstetrics and Gynaecology, Government Medical College, Kottayam, a tertiary care referral center providing comprehensive obstetric and neonatal services. Study Period The study was conducted over a period of six months, following approval from the Institutional Ethics Committee. Study Population The study population comprised antenatal women with singleton viable pregnancies beyond 34 weeks of gestation who were admitted to the labour room during the study period. Sample Size Calculation The sample size was calculated based on a previous study by Vidyasagara et al., which reported that 26.3% of pregnant women had abnormal amniotic fluid volume. Using the formula N = (Zα/2)² × p (1 − p) / d² with a confidence level of 95% (Z = 1.96), anticipated proportion (p = 0.263), and margin of error (d = 0.05), the calculated sample size was 351.49, which was rounded up to 360 participants. A total of 361 women were ultimately included in the study. Sampling Technique A purposive sampling technique was employed. Participants were categorized based on their amniotic fluid index values obtained from third-trimester ultrasonography. Inclusion Criteria Participants were included in the study if they: • Had singleton viable pregnancies beyond 34 weeks of gestation • Had undergone third-trimester ultrasonography with documented AFI • Had intact membranes at admission • Were aged 18 years or older Exclusion Criteria Participants were excluded if they had: • Congenital fetal anomalies • Premature rupture of membranes • Multiple pregnancies • Malpresentations • Post-term pregnancies Study Tool Data were collected using a structured, pre-designed proforma that included maternal demographic details, obstetric history, antenatal risk factors, AFI measurements, intrapartum events, and neonatal outcomes. Operational Definitions • Amniotic Fluid Index (AFI): Sum of the deepest vertical pocket of amniotic fluid measured in four uterine quadrants on ultrasonography. • Normal AFI: 5–25 cm • Oligohydramnios: AFI <5 cm • Polyhydramnios: AFI >25 cm Study Procedure Eligible participants were recruited at the time of admission to the labour room after obtaining written informed consent. AFI values were recorded from third-trimester ultrasound reports performed during routine antenatal care. Based on AFI values, participants were classified into normal AFI and abnormal AFI (oligohydramnios or polyhydramnios) groups. Participants were monitored throughout labour and delivery. Data on intrapartum events such as liquor status, mode of delivery, and indications for cesarean section were documented. Neonatal outcomes including birth weight, APGAR scores at 1 and 5 minutes (assessed by a pediatrician), presence of respiratory distress, NICU admission, hypoglycaemia, birth asphyxia, neonatal sepsis, hyperbilirubinemia, and neonatal mortality were recorded. Maternal and neonatal follow-up continued until four days postpartum. Data Management and Statistical Analysis Data collection was performed by a single observer to minimize inter-observer and information bias. Data were entered into Microsoft Excel and analyzed using SPSS version 26.0. Descriptive statistics were expressed as frequencies and percentages. Inferential analysis was carried out using the Chi-square test to assess the association between AFI status and fetomaternal outcomes. A p-value <0.05 was considered statistically significant.

A total of 361 antenatal women with singleton pregnancies beyond 34 weeks of gestation were included in the final analysis. Table 1: Demographic and Obstetric Characteristics of Study Participants (n = 361) Variable Category Frequency (n) Percentage (%) Maternal Age (years) 18–24 110 30.5 25–29 143 39.6 30–34 75 20.8 35–39 30 8.3 ≥40 3 0.8 Gestational Age at Delivery 34–36⁺⁶ weeks 27 7.5 37–38⁺⁶ weeks 200 55.4 39–40⁺⁶ weeks 131 36.3 41–42⁺⁶ weeks 3 0.8 BMI Category (kg/m²) <18.5 59 16.3 18.5–24.9 192 53.2 25–29.9 78 21.6 ≥30 32 8.9 Gravida Primigravida 206 57.1 Multigravida 155 42.9 AFI Status <5 (Oligohydramnios) 26 7.2 5–25 (Normal) 315 87.3 >25 (Polyhydramnios) 20 5.5 Most participants were aged 25–29 years (39.6%), primigravida (57.1%), and had normal BMI (53.2%). Normal AFI was observed in 87.3% of pregnancies. Table 2: Association Between Birth Weight Category and Amniotic Fluid Index (AFI) Status Birth Weight Category AFI <5 n (%) AFI >25 n (%) AFI 5–25 n (%) Total n (%) <1.5 kg (VLBW) 1 (3.8) 0 (0.0) 2 (0.6) 3 (0.8) 1.5–2.49 kg (LBW) 16 (61.5) 0 (0.0) 60 (19.0) 76 (21.1) 2.5–4.0 kg (Normal) 9 (34.6) 19 (95.0) 251 (79.7) 279 (77.3) >4.0 kg (Macrosomia) 0 (0.0) 1 (5.0) 2 (0.6) 3 (0.8) Total 26 (100) 20 (100) 315 (100) 361 (100) Chi-square = 39.93, p < 0.001 Low birth weight was significantly more common among oligohydramnios cases (61.5%), while normal birth weight predominated in normal AFI pregnancies. Table 3: Association Between APGAR Score at 1 Minute and AFI Status APGAR Score (1 min) AFI <5 n (%) AFI >25 n (%) AFI 5–25 n (%) Total n (%) 3 0 (0.0) 0 (0.0) 1 (0.3) 1 (0.3) 5 0 (0.0) 0 (0.0) 1 (0.3) 1 (0.3) 7 1 (3.8) 0 (0.0) 0 (0.0) 1 (0.3) 8 2 (7.7) 2 (10.0) 3 (1.0) 7 (1.9) 9 23 (88.5) 18 (90.0) 310 (98.4) 351 (97.2) Total 26 (100) 20 (100) 315 (100) 361 (100) Chi-square = 26.26, p = 0.001 Lower APGAR scores at 1 minute were significantly more frequent in abnormal AFI groups, particularly oligohydramnios. Table 4: Association Between NICU Admission and AFI Status NICU Admission AFI <5 n (%) AFI >25 n (%) AFI 5–25 n (%) Total n (%) No 8 (30.8) 8 (40.0) 243 (77.1) 259 (71.7) Yes 18 (69.2) 12 (60.0) 72 (22.9) 102 (28.3) Total 26 (100) 20 (100) 315 (100) 361 (100) Chi-square = 36.01, p < 0.001 NICU admission was significantly higher in neonates born to mothers with oligohydramnios and polyhydramnios. Table 5: Association Between Neonatal Morbidity and AFI Status Outcome AFI <5 n (%) AFI >25 n (%) AFI 5–25 n (%) Chi-square p-value Respiratory Distress 14 (53.8) 2 (10.0) 23 (7.3) 54.01 <0.001 Birth Asphyxia 2 (7.7) 0 (0.0) 2 (0.6) 11.15 0.004 Hypoglycaemia 1 (3.8) 5 (25.0) 11 (3.5) 19.43 <0.001 Neonatal Sepsis 0 (0.0) 0 (0.0) 1 (0.3) 0.15 0.929 Neonatal Mortality 0 (0.0) 1 (5.0) 0 (0.0) 17.10 0.055 Oligohydramnios was strongly associated with respiratory distress and birth asphyxia, while polyhydramnios showed a significant association with neonatal hypoglycaemia. No significant association was observed with neonatal sepsis or mortality.

Amniotic fluid plays a crucial role in fetal growth and development by providing mechanical protection, maintaining thermal stability, preventing umbilical cord compression, and facilitating normal pulmonary and musculoskeletal maturation. Alterations in amniotic fluid volume, reflected by abnormal amniotic fluid index (AFI), are widely recognized as indicators of fetal compromise and placental dysfunction. The present prospective observational study evaluated the association between AFI status and fetomaternal outcomes and compared the findings with existing literature to provide clinically relevant insights. In the present study, the majority of women were in the 25–29-year age group, which represents the peak reproductive age in the Indian population. This demographic pattern is consistent with observations by Sarmishta et al. [6], who also reported a predominance of younger women among pregnancies complicated by oligohydramnios. Most participants had a normal body mass index, although a notable proportion were underweight or overweight, suggesting that maternal nutritional status may act as an important contextual modifier of pregnancy outcomes. While many earlier studies did not emphasize maternal BMI, its inclusion in the present study strengthens the clinical interpretation of fetal growth outcomes. The distribution of AFI in this cohort showed that 87.3% of pregnancies had normal AFI, while oligohydramnios and polyhydramnios were observed in 7.2% and 5.5% of cases, respectively. These findings are comparable to those reported by Vidyasagara et al. [7], supporting the applicability of standard AFI cut-offs in routine clinical practice. The relatively lower prevalence of oligohydramnios in the present study may reflect effective antenatal surveillance and timely referral to a tertiary care center. Mode of delivery analysis revealed a high rate of vaginal births, with cesarean section performed in 13.9% of cases, mainly for fetal distress and meconium-stained amniotic fluid. This cesarean rate is lower than that reported by Chaudhary et al. [8] and Bhat et al. [9], who documented significantly higher operative delivery rates among women with oligohydramnios. The lower cesarean rate in the present study may be attributed to continuous intrapartum monitoring and judicious decision-making, as also suggested by Vasanthamani et al. [10], who demonstrated favorable outcomes in oligohydramnios cases with reactive non-stress tests. Meconium-stained amniotic fluid was observed in 8.6% of cases, which is considerably lower than rates reported by Chaudhary et al. [8] and Bansal et al. [11]. This reduction may be due to early identification of fetal compromise and timely obstetric intervention. Nevertheless, previous studies, including that by Patil and Shaikmohammed [12], have emphasized the association between oligohydramnios, meconium staining, and fetal distress, reinforcing the need for vigilant monitoring. Neonatal outcomes formed the core focus of this study. Low birth weight was observed in 21.1% of neonates, with a markedly higher prevalence (61.5%) among those born to mothers with oligohydramnios. This strong association supports the hypothesis that reduced amniotic fluid reflects chronic uteroplacental insufficiency leading to intrauterine growth restriction. Similar associations have been consistently reported by Mathuriya et al. [13], Patel et al. [23], Ravi et al. [6], Jagatia et al. [14], and Bhat et al. [9], reinforcing the biological plausibility of this finding. Respiratory distress was another significant neonatal morbidity observed in this study, affecting 10.8% of neonates overall and more than half of those in the oligohydramnios group. These findings align with those of Vyas et al. [12], Bansal et al. [11], and Guin et al. [19], who reported increased respiratory complications and NICU admissions in neonates born to mothers with abnormal AFI. Reduced amniotic fluid volume may impair lung development and increase the risk of perinatal hypoxia, explaining this association. Neonates born to mothers with abnormal AFI, particularly oligohydramnios, had significantly lower APGAR scores at one minute, although most showed recovery by five minutes. This transient compromise is consistent with findings by Chaudhary et al. [8], Sarmishta et al. [20], and Patil and Shaikmohammed [12], suggesting that while abnormal AFI may predispose to initial neonatal depression, effective resuscitation and intrapartum care can result in rapid stabilization. NICU admission was required in 28.3% of neonates, with significantly higher rates among oligohydramnios (69.2%) and polyhydramnios (60%) groups. These results closely mirror those reported by Vidyasagara et al. [7], Vyas et al. [12], Bhat et al. [9], and Guin et al. [19], all of whom documented increased neonatal morbidity and need for intensive care in pregnancies complicated by abnormal AFI. Additionally, polyhydramnios was associated with a higher incidence of neonatal hypoglycaemia, a finding supported by Bansal et al. [11], possibly reflecting underlying maternal metabolic conditions. Overall, the present study reinforces the clinical significance of amniotic fluid assessment in late pregnancy. Oligohydramnios, in particular, emerged as a strong predictor of adverse neonatal outcomes, including low birth weight, respiratory distress, lower initial APGAR scores, and increased NICU admissions. These findings are well supported by existing literature and underscore the value of AFI as a simple, non-invasive, and effective screening tool. Regular antenatal monitoring of AFI, combined with timely obstetric and neonatal interventions, has the potential to significantly reduce perinatal morbidity and improve neonatal outcomes.

This prospective observational study concludes that abnormal amniotic fluid index (AFI) in the third trimester is significantly associated with adverse neonatal outcomes, with oligohydramnios posing a particularly high risk. Pregnancies complicated by low AFI showed higher rates of low birth weight, lower APGAR scores at one minute, respiratory distress, birth asphyxia, and increased need for NICU admission, while polyhydramnios was mainly associated with neonatal hypoglycaemia and higher NICU admissions. In contrast, normal AFI was consistently linked with favorable perinatal outcomes. These findings highlight the clinical value of routine AFI assessment as a simple, non-invasive tool for early identification of high-risk pregnancies, enabling timely obstetric interventions and improved neonatal preparedness to reduce early neonatal morbidity. Conflict of interest: Nil

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