Gestational diabetes mellitus (GDM) is defined as carbohydrate intolerance resulting in hyperglycemia with first occurrence or detection during pregnancy. GDM is seriously harmful to both the woman and the fetus. GDM women are prone to complications of gestational hypertensive disease, polyhydramnios, and premature rupture of fetal membranes, infection and premature birth 7. In addition, the fetus is prone to spontaneous abortion, malformation and hypoxia even intrauterine death. More than 80% of pregnant women with diabetes have GDM. The prevalence of GDM in China is 4%-15%.The prevalence rate in North, central and East China is higher than that in other regions, and has a significant upward trend in recent years 8, 9. In this study, the ratio of GDM to non-GDM pregnant women was 1:8.1. GDM has great harm to both mothers and children. The etiology and pathogenesis are not yet clear, which may be related to environmental factors, genetic factors, insulin resistance, adipocytokine and inflammatory factors 10.
Studies have confirmed that vascular remodeling disorders at the maternal-fetal interface are widely associated with pregnancy complications. Vascular remodeling highly intensive in early pregnancy is an important determinant of pregnancy outcome 11–13.The uterine spiral artery passes through the placenta and provides the fetus with the nutrients needed for growth and development. In the first 3 months of pregnancy, the uterine spiral artery undergoes a recast process to establish enough blood perfusion placentas for optimal nutrition and metabolite exchange to meet the needs of the fetus 14, 15. In the recast process, the smooth muscle and elastic fibers of the uterine spiral artery medium disappear and are replaced by fibrinoid substances, and the lumen expands gradually from the distal end to the proximal end, resulting in decreased vascular bed resistance and increased blood flow 16, thus facilitating the occurrence and development of the placenta. Animal experiments have found that trophoblast infiltration and spiral artery remodeling disorders in diabetic rats may lead to placenta damage and insufficient nutrient supply, and ultimately lead to fetal weight loss 17. Hemodynamic changes of spiral arteries can be used to evaluate the process and degree of spiral artery recasting, which is closely related to placenta development. Currently, the most frequently studied hemodynamic parameter is PI, which is indirectly obtained by the formula and is not affected by the sample angle. PI is the ratio of peak systolic blood flow velocity to average blood flow velocity, which can comprehensively reflect the maximum and average blood flow velocity and vascular bed resistance. This study found that the uterine spiral artery PI in GDM group was higher than that in normal group in first-trimester. Therefore, it is speculated that the increase of PI may be related to the occurrence of GDM. The mechanism may be as follows: on the one hand, the GDM group may not meet the diagnostic criteria of elevated blood glucose during first-trimester, but has abnormal glucose tolerance, which is not conducive to the recast process of the uterine spiral artery; On the other hand, the increase of PI in the uterine spiral artery means increased blood supply resistance, which in turn affects the development of placenta. The placenta has an endocrine function, which can secrete estrogen, progesterone, placental lactin, cortisol, insulinase and other substances with insulin resistance 18. Placenta with abnormal development will directly affect hormone secretion, and the changes of hormones will lead to further changes in immune-endocrine regulation of the maternal-fetal interface, resulting in GDM. The specific mechanism remains to be confirmed by further studies.
The early screening of GDM is of great clinical significance, but at present, it is mainly carried out by oral glucose tolerance test (OGTT) at 24–28 weeks of gestation 19. The results of this study showed that there was no significant difference between GDM and normal pregnant women in conventional obstetric color Doppler ultrasonography, that is, GDM could not be predicted by two-dimensional images or color Doppler. When measuring the hemodynamic parameters of uterine spiral arteries, it was found that the PI value of the GDM group was higher than that of the normal group, and the difference was statistically significant. Moreover, it was found by ROC curve that the sensitivity and specificity of GDM prediction were 90.5% and 73.3% when PI increased by more than 0.675 as the threshold value. The area under ROC curve was 0.861, indicating that PI had a certain predictive value for GDM, that is, it was feasible to predict the occurrence of GDM by measuring PI value of uterine spiral artery at 11 ~ 13 + 6 weeks of gestation. In conclusion, the changes of uterine spiral artery hemodynamics at 11 ~ 13 + 6 weeks of pregnancy may be related to the occurrence of GDM, and the PI value of uterine spiral artery has certain value in predicting GDM.