The role of the ratio of first trimester CRL (crown rump length) measurement to NT (nuchal translucency) measurements in predicting early-onset fetal growth restriction (FGR)

Abstract

Objective: Our aim is to evaluate the role of the ratio of first-trimester CRL (crown rump length) measurement to NT (nuchal translucency) measurements in predicting early-onset fetal growth restriction (FGR) and to contribute to the existing literature. Methods: In the present case-control study, fetuses with early-onset FGR were compared to a frequency matched low risk control group. This study was conducted in the perinatology clinic of Ankara Bilkent City Hospital between 2020 and 2023. Maternal age, gravidity, parity, crown-rump length (CRL), and nuchal translucency (NT) measurements were compared between pregnant women with early onset FGR (n=39) and pregnant women without FGR (n=50). Results: The mean age of pregnant women with FGR who participated in the study was 27.1±0.8, and the mean age of pregnant women without FGR was 26.3±0.6, and no statistically significant difference was found between the two groups (p=0.4)). Mean CRL was 54.98±1.08 mm in the group with FGR and 56.99±1.11 mm in the group without FGR; there was no significant difference between the two groups (p=0.2). The NT value was 1.11 ± 0.04 mm in the FGR group and 1.13 ± 0.02 mm in the without FGR group, there was no significant difference between the two groups (p=0.73). The mean CRL/NT ratio was 52.00±2.33 in the group with early onset FGR and 51.46±1.48 in the group without FGR and there was no statistically significant difference between the two groups (p=0.83). When the early developing FGR group is evaluated within itself, the mean age at diagnosis was 31.7±0.3 weeks. EFW mean percentile at diagnosis was 4.5±0.6 and ac percentile was 2.9±0.4. The mean umbilical artery systole/diastole ratio (UA-SD) was 2.9±0.16 and the mean umbilical artery pulsatility index (UA-PI) was 1.02±0.05. Conclusion: Crown-rump length to nuchal translucency ratio is not clinically useful to predict early-onset FGR.