Background/Objectives: Gestational diabetes mellitus (GDM) is one of the most common morbidities of pregnancy. The impact of increased maternal blood glucose on fetoplacental hemodynamics is not fully elucidated, especially in patients with uncontrolled GDM necessitating insulin therapy. The objective of this study was to assess the impact of insulin therapy on the umbilical artery dopplers in GDM pregnancies adequate for gestational-age fetuses. Methods: Retrospective observational study among 447 GDM pregnant women, divided according to their treatment (nutritional therapy (NT), long acting (LA) insulin, combined insulin) and 100 healthy controls with the same gestational age. The umbilical artery pulsatility index (UA-PI) was recorded at 28, 32 and 36 weeks. Results: UA-PI values declined in both GDM and healthy controls at all three time intervals. The combined insulin group showed reduced UA-PI values in comparison to the LA insulin group, but the difference never reached statistical significance. The combined insulin group exhibited significantly reduced UA-PI values at 32- and 36-weeks’ gestation compared to the NT groups. Conclusions: A decreased impedance to blood flow in the umbilical artery of diabetic mothers on insulin therapy was observed. This was more pronounced during the last trimester. The extent to which umbilical artery PI can predict unfavorable outcomes has yet to be determined. Further additional studies are necessary to confirm the precise impact of glucose levels and medical interventions on the circulation of both the fetus and the mother.

Objectives: Excessive fetal growth is the most common fetal complication associated with gestational diabetes (GDM), resulting in adverse short- and long-term outcomes. Our main objective was to evaluate the influence of excessive fetal growth on Doppler ultrasonographic measurements of the Umbilical Artery (UA) among women with GDM during the third trimester of pregnancy. Methods: A retrospective study among 472 women with GDM was conducted. UA-PI was measured by Doppler ultrasonography three different times during the third trimester of pregnancy at 28, 32, and 36 weeks. Pregnancies were grouped according to the fetal weight centile or birthweight in two groups: large for gestational age (LGA) group (>90th percentile or ≥4000 g at birth) and adequate for gestational age (AGA) group (<90th percentile or <4000 g at birth, not including the intrauterine growth restrictions). Results: In the LGA group (n = 57, 12.1%), women had higher BMI (p = 0.0001) and fasting blood glucose than the AGA group (97.08 ± 40.69 vs. 86.29 ± 39.58 mg/dL; p = 0.0550). They required insulin therapy more frequently to achieve glycemic control (63.2% vs. 34%, p = 0.0001). In LGA, UA-PI decreased progressively from 28 to 36 weeks (p = 0.0048). The most pronounced reduction occurred at 32 weeks (p = 0.0076). Conclusions: All fetuses from mothers with GDM had a significant and progressive decline in UA-PI during the third trimester of pregnancy. LGA fetuses showed lower UA-PI values compared with AGA fetuses. Since maternal hyperglycemia increases the risk of fetal overweight and GDM may represent a fetal vascular disorder, it therefore seems possible that in LGA fetuses, maternal hyperglycemia could influence the fetal vasculature.