Does detection of a large for gestational age (LGA) fetus in fetal anomaly scan (FAS) require an early oral glucose screening test (OGTT) and can LGA fetus be detected at birth?

OBJECTIVE: Gestational diabetes mellitus (GDM) complications increase with late diagnosis and late treatment, so early diagnosis and treatment is one of the most important factors in preventing complications. We tried to find an answer to the question of whether the detection of large for gestational age (LGA) fetus in fetal anomaly scan (FAS) requires earlier oral glucose screening test (OGTT) and predicts LGA fetus at birth. PATIENTS AND METHODS: Pregnant women who underwent fetal anomaly scan and gestational diabetes screening at the Department of Obstetrics and Gynecology, University of Health Sciences, Tepecik Training and Research Hospital between 2018 and 2020 were included in this large retrospective cohort study. FAS was routinely performed between 18-22 weeks in our hospital. 75 grams of OGTT was used for gestational diabetes screening and it was performed between 24-28 weeks. RESULTS: This large retrospective cohort study was performed on 3,180 fetuses, 2,904 appropriate for gestational age (AGA) and 276 LGA, in the second trimester. The prevalence of GDM was significantly higher in the LGA group (OR 2.44, 95% CI 1.66-3.58; p < 0.001). Insulin requirement for blood glucose regulation was significantly higher in the LGA group (OR 3.6, 95% CI 1.68-7.7; p = 0.001). Fasting and 1st hour OGTT values were similar between the groups, but 2nd hour OGTT values were significantly higher in the second trimester LGA group (p = 0.041). The prevalence of LGA newborns at birth was higher in second trimester LGA fetuses than in fetuses with AGA (21.1% vs. 7.1%, p < 0.001). CONCLUSIONS: The fact that the estimated fetal weight (EFW) measured in the second trimester FAS is LGA may be related to GDM in the future and LGA fetus at birth. A more detailed GDM risk questioning should be performed to these mothers and OGTT should be considered when additional risk factors are detected. In addition to all these, glucose regulation may not be possible with diet alone in mothers who have LGA in the second trimester ultrasound and who may have GDM in the future. These mothers should be monitored more closely and more carefully.