Evidence that Systemic Vascular Resistance is increased prior to the development of Gestational Diabetes Mellitus.

Background: The ophthalmic artery, which is the first branch of the internal carotid artery, has a Doppler velocity waveform with two systolic peaks. The ratio of the peak systolic velocity (PSV) of the second wave divided by that of the first wave, reflects increased peripheral resistance. Previous studies in the first, second and third trimesters of pregnancy have reported that in pregnancies that subsequently develop preeclampsia (PE) the PSV ratio is increased. Both PE and gestational diabetes mellitus (GDM) are associated with endothelial dysfunction and an increased risk of cardiovascular diseases during the first decade following pregnancy.

Objectives: To compare the ophthalmic artery PSV ratio at 11-13 weeks' gestation in women who subsequently develop GDM to unaffected pregnancies and those who develop PE.

Study design: This was a prospective observational study in women attending for a routine hospital visit at 11⁺⁰ - 13⁺⁶ weeks' gestation at King's College Hospital, London, UK. This visit included recording of maternal demographic characteristics and medical history, ultrasound examination for fetal anatomy and growth, assessment of flow velocity waveforms from the maternal ophthalmic arteries and calculation of the PSV ratio, and measurement of mean arterial pressure (MAP). Linear regression was performed for the prediction of ophthalmic artery PSV ratio, from maternal characteristics and MAP. The PSV ratio in the group with GDM was compared to that of PE and unaffected pregnancies.

Results: 3999 women were included in the study, including 375 (9.8%) who developed GDM and 101 (2.5%) who developed PE. In the GDM group, 161 (43.3%) were treated by diet alone, 130 (34,1%) were treated with metformin and 84 (22.6%) received insulin ± metformin. Significant prediction of PSV ratio was provided by development of PE, maternal age, body mass index, MAP, first degree family history of diabetes mellitus, family history of PE, Asian ethnicity, and smoking. There was no significant contribution from GDM. In women who developed GDM requiring insulin treatment, ophthalmic artery PSV ratio (0.67 ± 0.09) was higher (p <0.001) than in unaffected pregnancies (0.63 ± 0.10), but it was not significantly different from that in the PE group (0.69 ± 0.10; p=0.90).

Conclusions: In women who develop severe GDM, requiring insulin treatment, there is evidence of increased peripheral resistance which is apparent from the first-trimester of pregnancy.