Antenatal Umbilical Coiling Index as a Predictor of NICU Admission as Fetal Adverse Outcome Using Color Doppler in the third trimester-A Nested Case Control Study

Background: The umbilical cord is extremely important for the developing foetus because it transports deoxygenated blood to the placenta through two umbilical arteries and supplies the foetus with oxygenated blood through the umbilical vein. Umbilical cord coiling increases the chord's flexibility and tensile strength, while also offering resistance to outside pressures that might interrupt the fetus's blood supply.
Objective: To determine the correlation between antenatal umbilical coiling index (UCI) and neonatal intensive care unit (NICU) admission as a fetal adverse outcome using color Doppler.
Methodology: This nested case-control study was conducted on pregnant women attending to Ain Shams University Maternity Hospital Outpatient Department Ultrasound Clinics for antenatal care during the period from May 2021 until December 2022.
Results: Regarding coiling index, it was statistically significantly higher among cases of NICU group compared to controls (0.53 ± 0.14 vs. 0.48 ± 0.11). There was a statistically significant higher frequency of hypercoiling in NICU group compared to non-NICU group. Regarding umbilical artery resistance index (URI), our study revealed that it was statistically significantly higher among cases of NICU group compared to control one (0.64 ± 0.08 vs. 0.60 ± 0.04). URI and UCI (< 75%) were unreliable in predicting NICU admission; AUC (area under the curve) was 71% for URI and 65% for UCI. On the other hand, URI was reliable in predicting hyper-coiling (as an indicator of adverse outcome) P<0.0001 and AUC was 77. The best cut-off value of URI was 0.61 with a sensitivity of 77%, specificity of 56%, PPV of 64% and NPV of 71% with a diagnostic accuracy of 66%. Women whose neonates have been admitted to NICU showed significantly higher rates of CS, low APGAR score and preterm labor when compared to women whose neonates have not (p < 0.05).
Conclusion: Umbilical coiling index was positively correlated with umbilical artery resistance index, denoting that hyper-coiling correlates with increased resistance to blood flow in the umbilical cord, but there was no statistical evidence of using UCI as predictor of NICU admission in the current study. Umbilical cord coiling may be used as a simple method to detect placental insufficiency as it positively correlated with the umbilical artery RI even without using color Doppler.