Cerebroplacental Ratio in Monochorionic Diamniotic Twin Pregnancies with and Without Gestational Diabetes: A Longitudinal Cohort Study

Objective: To investigate whether gestational diabetes mellitus (GDM), including insulin-treated GDM, affects cerebroplacental ratio (CPR) values in monochorionic diamniotic (MCDA) twin pregnancies. Methods: This retrospective single-center cohort study included a total of 262 MCDA twin pregnancies managed at a tertiary referral center, comprising pregnancies without GDM (n = 120), with diet-controlled GDM (n = 80), and with insulin-treated GDM (n = 62). Doppler ultrasound examinations were performed at three gestational time points between 24 and 36 weeks of gestation. CPR, umbilical artery pulsatility index (UA-PI), and middle cerebral artery pulsatility index (MCA-PI) were compared longitudinally between groups. Doppler indices were compared between groups without adjustment for baseline differences such as BMI and parity Results: Maternal body mass index was significantly higher in pregnancies complicated by GDM, particularly in those requiring insulin therapy (p < 0.001). Estimated fetal weight was higher in the insulin-treated GDM group at mid-gestation (28–32 weeks; p = 0.01). However, CPR values remained within normal ranges throughout all screening points across all three groups. No relevant differences in UA-PI, MCA-PI, gestational age at delivery, Apgar scores, or umbilical cord pH were observed between groups. Conclusions: In MCDA twin pregnancies, gestational diabetes—regardless of insulin treatment—does not appear to significantly influence cerebroplacental ratio values throughout gestation. No statistically significant differences in CPR values were observed between groups. No statistically significant differences in CPR values were detected between groups. However, given the exploratory design and lack of adjustment for confounders, subtle effects cannot be excluded. The clinical utility of CPR in this population requires further investigation.