The impact of increased nuchal translucency on pregnancy outcomes: A retrospective cohort study in Qatar

Background: Nuchal translucency (NT) measurement by ultrasound is used in the first trimester as a screening tool for genetic, chromosomal, and structural anomalies. As the NT measurement increases, the risk of an underlying abnormality also rises. This study aims to evaluate the significance of increased NT measurements within a local cohort, examining their associations with adverse pregnancy outcomes and their potential role in guiding clinical interventions. Methods: Pregnancies with first-trimester fetal NT measurements greater than 2.5 mm were included. Participants were categorized into five groups based on NT measurements: ≤3.4 mm, 3.5–4.4 mm, 4.5–5.4 mm, 5.5–6.4 mm and ≥6.5 mm. The outcomes evaluated included chromosomal anomalies confirmed by invasive testing (such as Trisomy 21), major congenital anomalies involving any major organ system, and miscarriage or termination of pregnancy before 24 weeks of gestation. Gestational age at delivery, birthweight, small-for-dates (SFD) status, and admission to the neonatal intensive care unit (NICU) were evaluated for infants born after 24 weeks of gestation without congenital anomalies. Results: The median NT measurement among the 290 women in the study was 3.7 mm, ranging from 2.9 mm (25th centile) to 7.4 mm (75th centile). Overall, 43.5% of the participants were in the lowest NT category, while 15.9% were in the highest category. Maternal age, body mass index, and nationality were comparable between the groups. The odds of chromosomal anomalies increased with higher NT measurements, with odds ratio (OR) ranging from 2.50 to 4.02 ( p < 0.05), compared to the lowest NT group. Similarly, the odds of major congenital anomalies (OR: 2.20–4.20; p < 0.05), multiple anomalies (OR: 5.61–8.19 in the highest three categories; p < 0.005), and miscarriages (OR: 5.04–14.9 in the highest three categories; p < 0.001) all increased with rising NT measurements. The odds of most chromosomal anomalies increased with NT, except for Trisomy 21, which was similar across the groups. Participants in the two lowest NT groups had 12.7- and 7.5-fold higher odds (both p < 0.001) of achieving a pregnancy beyond 24 weeks without anomalies compared to those in the highest NT group. Among pregnancies resulting in viable non-anomalous deliveries, there were no significant differences in the gestational age at delivery, birthweight, incidence of SFD, or NICU admission. Conclusion: Adverse outcomes, including chromosomal and congenital anomalies, increased with higher NT measurements, with a significant difference observed beyond 3.4 mm. These findings highlight the importance of early NT screening and targeted interventions to improve perinatal outcomes.