Subject baseline characteristics
The baseline characteristics of the cohort study were demonstrated in Table 1. Altogether, two hundred and twenty-one participants with the average age of 33.8 years old as well as pre-pregancy BMI of 22.1kg/m2 were included in our study, among which 85 participants(38.5%) were of advanced age and 73 women(34%) were defined as overweight. The mean OGTT results were 4.5, 9.8, and 8.9 mmol/L for fasting, 1 hour and 2 hours after glucose load respectively. Furthermore, the mean HbA1c value before delivery is 5.3%(34mmol/mol), with 14 participants (6.3%) defined as poorly glycemic controlled cases.
Figure 1 showed the three trajectories of each lipid(TC, TG, LDL-C, and HDL-C) during pregnancy established as low, moderate, and high trajectory using GBTM. Throughout the pregnancy, all three trajectories showed elevation except for HDL-C, which firstly raised to reach the maximum at mid-trimester and slightly fell off at late-pregnancy. Among four sets of trajectories, the high-level trajectory of TC, TG, and LDL-C included the least number of individuals while the low-level trajectory of HDL-C showed to have the least members, which indicated that most participants only suffered from relatively slight dyslipidemia during pregnancy.
Subjects characteristics at postpartum period
The postpartum data of study subjects were as depicted in Table 2. The postpartum BMI was slightly increased to 22.6kg/m2 with average weight retention of 1.4kg among all participants. The number of overweight subjects was 86, which remained the same compared with prepregnancy data. The postpartum OGTT was performed at 7.7±1.6 weeks after delivery. According to OGTT results after delivery, 73 participants developed glucose intolerance postpartum, which means almost a third of GDM women developed glucose intolerance in our study. The mean incidence rates of IFG, IGT, prediabetes, type 2 diabetes among women with postpartum OGTT results, were 0.9%, 29.9%, 30.8%, and 2.3%, respectively. Instead of falling back to starting levels, the LDL-C levels postpartum in three trajectories were all found increased markedly with the rise of LDL-C during pregnancy (P<0.01), which were highest in high trajectory and lowest in low trajectory.
Association of lipids trajectories with postpartum dyslipidemia
As shown in Table 3, when compared with T1, all lipids except HDL-C presented elevated incidence of post-delivery dyslipidemia with significant differences. Risk of developing dyslipidemia after giving birth became significantly higher in GDM women with a higher trajectory of lipid profile such as TC, TG, and LDL-C. After controlling potential confounders, the above significance still existed. No difference was established between different trajectories of HDL-C with risk of post-delivery dyslipidemia in the study.
Association of lipids trajectories with postpartum glucose intolerance
Among all these data represented glucose metabolism of GDM patients after giving birth, we noticed that the rate of glucose intolerance slightly decreased with ascending trajectory of LDL-C(P=0.08). The incidences of glucose intolerance decreased along with the low, moderate, and high level of LDL-c trajectories, which were 38.4%, 34.9%, and 17.9% respectively. It was evident the incidence of glucose intolerance in low trajectory(38.4%) was significantly higher compared with that in high trajectory(17.9%) (P=0.03). Accordingly, HOMA-IS, the index represented insulin sensitivity, increased significantly across the three subgroups from low to high trajectory(P=0.02). Similarly, the postpartum level of ISOGTT was highest in the low trajectory and lowest in the high trajectory(P=0.04).
As for other lipids including TC, TG, and HDL-C, no different risks of developing glucose intolerance after delivery were found between various levels of trajectories(Table 4).
For baseline characters among LDL-C trajectories, a lower prepregnancy overweight rate was observed in moderate trajectory (24.8%), while higher ones were found in low(42.5%) and high trajectory(42.5%), which were statistically different(P=0.03). Other potential risk factors both during gestation(Table 1) and after delivery(Table 2) were found balanced between three trajectories. Since medication for treating hyperlipemia is not available for pregnant women in China, none of our participants acquired lipids concentration reduction with medication.
Table 4 showed the unadjusted and adjusted OR of postpartum glucose intolerance with the high trajectory as the reference in multivariable logistic regression models. The risks of postpartum aberrant glucose tolerance were increased markedly in low trajectory and moderate trajectory, in which the unadjusted odds ratio were 2.84 (95% CI: 1.11-7.31) and 2.45(95% CI: 0.99-6.06), respectively(Table 4, Model I). The increased tendency still held after adjusting confounders(Table 4, Model II, Model III). In Model II, significantly elevated incidences of postpartum glucose intolerance were revealed in low trajectory(OR, 3.30; 95% CI, 1.25-8.72) and moderate trajectory(OR, 2.87; 95% CI, 1.13-7.29). Moreover, compared with the reference, the OR of low trajectory was 3.13(95% CI: 1.17-8.39) and of moderate trajectory was 2.68(95% CI: 1.05-6.85) with statistically significance (P=0.02 and 0.04 respectively) after adjusting for underlying confounders including OGTT.
At last, figure 2 shows the association between LDL-C trajectory and maternal glucose intolerance by stratified analysis. No significant interaction effects were identified for potential risk factors including maternal age, multiparity, prepregnancy BMI, family history of diabetes, and mode of delivery.