Perinatal outcomes in growth restricted fetuses

Intrauterine growth restriction (IUGR) refers to the failure of a fetus to achieve its genetically determined growth potential due to pathological conditions. It complicates approximately 3–9% of pregnancies in developed countries, with a substantially higher burden reported in developing countries.¹ IUGR should be distinguished from small for gestational age (SGA), which describes a fetus with an estimated fetal weight below the 10th percentile or below −2 standard deviations for gestational age without necessarily indicating an underlying pathological process.^2,3 Antenatal identification of fetal growth restriction relies on clinical assessment, serial ultrasonography, and Doppler velocimetry. The Doppler parameters include PI(pulsatility index), RI(resistive index) and systolic-to-diastolic (S/D) ratio. Among Doppler parameters, the umbilical artery systolic-to-diastolic (S/D) ratio is an important indicator of placental vascular resistance; an increased S/D ratio reflects impaired placental perfusion and is associated with adverse perinatal outcomes.²

 Adequate placental perfusion is essential for normal fetal growth. Abnormal placentation and impaired development of the placental villous tree can increase vascular resistance and compromise maternal–fetal exchange, resulting in fetal growth restriction.³ Several maternal factors are associated with IUGR, including hypertensive disorders of pregnancy, diabetes mellitus, advanced maternal age, low maternal body mass index, inadequate maternal nutrition, and a previous history of an IUGR.^4–7 Maternal nutritional deficiency is particularly important in low-resource settings because it is potentially modifiable and may coexist with other socioeconomic and obstetric risk factors.

 Fetuses with IUGR are at increased risk of adverse perinatal outcomes, including stillbirth, preterm birth, neonatal hypoglycaemia, hypothermia, jaundice, respiratory distress syndrome, intraventricular haemorrhage, necrotising enterocolitis, and neonatal death.⁵Perinatal asphyxia is a frequent complication among growth-restricted fetuses.⁶ there has been reported an approximately two-fold increase in mortality among fetuses with growth restriction.⁷ Abnormal umbilical artery Doppler indices, particularly an S/D ratio >3, have also been associated with increased respiratory morbidity, low Apgar scores, and neonatal mortality.^8,9 Similarly, previous studies have demonstrated higher rates of neonatal intensive care unit (NICU) admission, metabolic acidosis, and perinatal mortality among SGA/IUGR fetuses compared with appropriately grown fetuses.^10,11

 Despite advances in antenatal surveillance, the identification of fetuses at greatest risk of adverse neonatal outcomes remains challenging, particularly in resource-constrained settings where maternal malnutrition and other risk factors for placental insufficiency are prevalent. Assessment of umbilical artery Doppler may provide an important tool for risk stratification and timely obstetric intervention. However, data regarding the relationship between antenatal Doppler abnormalities and specific perinatal outcomes remain limited in our setting.

 Therefore, this study was conducted to determine the perinatal outcomes of fetuses diagnosed antenatally with IUGR using ultrasonography and Doppler studies and to evaluate the prognostic value of the umbilical artery Doppler S/D ratio in predicting adverse neonatal outcomes.

This study evaluated maternal, fetal, anthropometric and Doppler factors associated with adverse perinatal outcomes among 367 pregnancies. Prematurity was observed in 40.6% of neonates, respiratory distress in 25.3%, and NICU admission in 44.5%, while 92.9% had a birth weight below 2500 g. The high frequency of low birth weight and prematurity in the present study indicates a substantial burden of adverse neonatal outcomes in this population. Maternal diabetes mellitus, hypertensive disorders of pregnancy, previous low birth weight, BMI, renal disease, autoimmune disorders, mode of delivery, fetal anthropometric measurements and umbilical artery Doppler findings were among the factors associated with one or more adverse outcomes. Our study's high NICU admission rate highlights the need for improved neonatal intensive care services in locations with limited resources and indicates the substantial infant morbidity linked to placental insufficiency.

Maternal BMI was significantly associated with poor perinatal outcomes including respiratory distress and NICU admission. This finding is consistent with previous evidence indicating that increased maternal BMI may adversely influence neonatal outcomes. It has been reported in a study that maternal obesity was significantly associated with NICU admission among near-term and term infants, with the association becoming stronger with increasing severity of obesity.¹² More recent population-based evidence has also demonstrated that maternal BMI ≥30 kg/m² is associated with an increased risk of neonatal respiratory morbidity, including respiratory distress syndrome.¹³ The significant association with respiratory distress and NICU admission supports the importance of appropriate maternal weight assessment and management during pregnancy.

A previous history of low birth weight was significantly associated with prematurity in the present study. This observation agrees with evidence that adverse outcomes may recur across successive pregnancies. A systematic review identified previous adverse pregnancy outcomes and obstetric factors among important predictors of recurrent low birth weight, intrauterine growth restriction and prematurity.¹⁴ Similarly, a cohort study from Brazil found that recurrence of low birth weight was particularly associated with a previous preterm birth and higher parity.¹⁵ another study also demonstrated that a previous low-birth-weight infant was associated with lower birth weight and smaller anthropometric measurements in a subsequent pregnancy.¹⁶ These findings suggest that previous poor obstetric outcomes may identify women requiring closer antenatal surveillance in subsequent pregnancies.

Diabetes mellitus was significantly associated with fetal growth restriction and prematurity in the current study, with diabetes present in 45.2% of mothers of premature neonates compared with 29.7% of mothers of term neonates. This finding is consistent with extensive evidence linking maternal diabetes with adverse pregnancy outcomes. A large meta-analysis reported significantly increased risks of preterm delivery and NICU admission among pregnancies complicated by pregestational diabetes.¹⁷ Similarly, a recent systematic review and meta-analysis involving more than 137 million pregnancies found that pregestational diabetes was associated with increased risks of preterm delivery, low APGAR score, NICU admission, stillbirth and perinatal mortality.¹⁸

 Hypertensive disorders showed particularly important associations with fetal growth restriction and adverse neonatal outcomes. Pregnancy-induced hypertension was significantly associated with respiratory distress and NICU admission, while pre-eclampsia was associated with prematurity, respiratory distress and NICU admission. These findings are strongly supported by previous research. In a large prospective cohort of 185,687 singleton births, maternal hypertension and pre-eclampsia were associated with increased risks of neonatal respiratory disorders, while pre-eclampsia was specifically associated with respiratory distress syndrome.¹⁹ Furthermore, pre-eclampsia has been shown to remain associated with NICU admission and respiratory distress even after accounting for the effect of preterm delivery, suggesting that its influence may extend beyond prematurity itself.²⁰ The higher frequency of prematurity and neonatal respiratory morbidity among pregnancies complicated by pre-eclampsia in the present study may therefore reflect both placental dysfunction and the need for earlier delivery because of maternal or fetal compromise.

 Mode of delivery was significantly associated with respiratory distress and NICU admission. Caesarean delivery was much more frequent among premature neonates than among term neonates (86.0% vs 62.7%) consistent with iatrogenic preterm birth due to fetal growth restriction. Similar associations between caesarean delivery and neonatal respiratory morbidity have been reported previously. A study of term neonates identified caesarean delivery as a strong risk factor for respiratory distress syndrome, while multiparity was also independently associated with respiratory morbidity.²¹ Another study demonstrated associations between caesarean delivery, neonatal respiratory distress and NICU admission.²² However, the relationship between mode of delivery and neonatal outcomes should be interpreted cautiously because caesarean delivery may be performed because of pre-existing fetal or maternal complications, including, previous cesarean delivery, non-progress of labour ,antepartum hemorrhage , chorioamnionitis etc. Thus, the observed association may partly reflect indication for caesarean delivery rather than the procedure itself.

 The present study also demonstrated significant associations between fetal anthropometric measurements and adverse outcomes. Birth length and head circumference were significantly lower among premature neonates, those with respiratory distress, those requiring NICU admission and those with lower birth weight. Estimated fetal weight and abdominal circumference also differed significantly across several adverse outcomes. These findings are clinically plausible because reduced fetal growth and smaller anthropometric measurements often accompany prematurity and placental insufficiency.

 The umbilical artery S/D ratio demonstrated significant associations with prematurity, respiratory distress and NICU admission. This is consistent with evidence that increased umbilical artery resistance reflects impaired placental vascular function and is associated with adverse perinatal outcomes. A study reported that persistently elevated umbilical artery S/D ratios were associated with increased preterm delivery, NICU admission and lower birth weight.²⁴ The present findings therefore support the clinical value of umbilical artery Doppler assessment for identifying pregnancies at increased risk of adverse neonatal outcomes. In this study after establishing the diagnosis of IUGR the monitoring was done with serial growth scans and repeated ultrasound dopplers. The decision of delivery was made on the basis of worsening Doppler parameters, abnormal CTG (cardiotocography) and abnormal ductus venosus in those with absent diastolic flow.

 Overall, the findings indicate that adverse perinatal outcomes in this study were multifactorial, involving maternal hypertensive disorder, previous obstetric history, fetal characteristics, anthropometric parameters and placental blood-flow indices. The strongest and most consistent associations were observed for maternal hypertension/pre-eclampsia, BMI, previous low birth weight, diabetes, mode of delivery and umbilical artery Doppler findings. These results emphasize the importance of early identification of high-risk pregnancies, optimization of maternal metabolic and hypertensive conditions, serial fetal growth assessment and appropriate Doppler surveillance. Because the present analysis primarily examined unadjusted associations, the observed relationships should not be interpreted as independent causal effects. Future studies using multivariable regression models would be useful to determine which maternal and fetal factors independently predict prematurity, respiratory distress, NICU admission and low birth weight.

This study demonstrated that adverse perinatal outcomes were associated with a range of maternal, fetal and placental factors. Maternal diabetes mellitus was significantly associated with prematurity, while pregnancy-induced hypertension and pre-eclampsia were associated with respiratory distress, NICU admission and prematurity. Maternal BMI, previous history of low birth weight, renal disease, autoimmune disorders and mode of delivery were also associated with selected adverse outcomes. anthropometric measurements, estimated fetal weight and abnormal umbilical artery Doppler indices were associated with adverse neonatal outcomes. These findings highlight the importance of early identification and close antenatal surveillance of high-risk pregnancies, particularly those complicated by fetal growth abnormalities, diabetes and hypertensive disorders. Appropriate maternal disease control, serial fetal growth assessment and umbilical artery Doppler monitoring may facilitate timely intervention and potentially improve perinatal outcomes.

Conflict of Interest: Nil

Funding: Nil

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