This was a retrospective cohort study.
From May 2013 to July 2019, we recruited all women with GDM at the Gestational Diabetes Mellitus Care Center of the Fifth People’s Hospital of Shanghai, Fudan University.
The health card of all pregnant women was established from gestational 10 weeks to 12weeks. The healthy card obtained information about age, last menstruation, method of conception, parity, obstetric history, family history of diabetes, previous history of GDM, and pre - pregnancy weight. Meanwhile, at the first visit, at the time of performing oral glucose tolerance test (OGTT) and at the time of one week before delivery, routine physical examinations blood pressure (BP), weight, blood count (Sysmex XN9000, Japan), biochemical tests (Cobas 8000, Germany)) were employed. Blood tests were performed in the morning after an overnight fast of at least 8 hours. BP was measured on two occasions 6 hours apart, BMI was calculated as weight in kilograms divided by the square of height in meters. Total gestational weight gain (GWG) and the rate of weight gain during intervention was categorized into three groups by the 2009 Institute of Medicine recommendations[11]: (1) inadequate weight gain; (2) adequate weight gain; (3) excessive weight gain.
Gestational hypertension (GH) was defined as a systolic blood pressure (SBP) ≥ 140 mmHg and / or a diastolic blood pressure (DBP) ≥ 90 mmHg on two occasions at least 6 hours apart after 20 weeks of gestation in a woman with previously normal blood pressure.
All subjects with the exception of those diagnosed with overt diabetes or GDM in early pregnancy underwent routine screening for GDM at 24–28 weeks’ gestation according to a 75g OGTT. A diagnosis of GDM was based on ADA diagnostic criteria.
The values for Homeostatic Model Assessment of Insulin Resistance (HOMA - IR) and Homeostatic Model Assessment of Insulin Sensitivity (HOMA - β) were determined from fasting plasma glucose and insulin concentration (Electrochemiluminescence, Cobas e602, Germany) [12]. Area under blood glucose (BG) curve was roughly calculated as \(\frac{1}{2}\times \left(\text{f}\text{a}\text{s}\text{t}\text{i}\text{n}\text{g} \text{b}\text{l}\text{o}\text{o}\text{d} \text{g}\text{l}\text{u}\text{c}\text{o}\text{s}\text{e} \right(\)FBG) + 1 hour BG) + \(\frac{1}{2}\times\)(1 hour BG + 2 hours BG)
Mothers with GDM were recommended to start lifestyle intervention immediately when the diagnosis of GDM was determined until to delivery. The time of GDM diagnosis was defined the initiating intervention pregnant week. GDM women should go quickly for a 30 - min walk every day, at least three days per week, together with a medical nutrition therapy and weight management. If the glycemic control was not aiming for the targets recommended by the Fifth International Workshop - Conference on GDM (Fasting glucose, 5.3 mmol/L or 1 hour postprandial glucose, 7.8 mmol/L or 2 hours postprandial glucose, 6.7 mmol/L)[13], insulin injection was started with continuous lifestyle therapy after one week according to ADA recommendations. Changes of weight and blood pressure were observed from the time of GDM diagnosis to one week before delivery.
After delivery, details including gestational age at delivery, treatment protocol for lowering glycemia, birth weight, and gender of the neonate were recorded by medical staff.
Women were excluded from the study for any of the following: ⑴ pre-existing DM; ⑵ chronic hypertension; ⑶renal disease history; ⑷ multiple gestation; (5) serious liver dysfunction (alanine transaminase above 2.5 times upper limitation) and renal dysfunction (estimated Glomerular Filtration Rate below 90 ml/min/1.73m2). Finally, 708 GDM women were entered in the analysis. Retrospective analysis processes were shown in Fig. 1.
Statistical analysis
Descriptive statistics for studied variables are presented as mean ± standard deviation (SD) for normally distributed variables, median (interquartile range (IQR)) for non - normally distributed variables, and frequency (percentage) for categorical variables. Student’s t - test or Mann - Whitney U tests were used to identify difference in mean between groups. HOMA - IR and HOMA - β were log transformed previously for t tests. In order to eliminate the confounder of the initiated time of controlling glycemia, a case - control matching method was employed to match variables of OGTT gestational weeks. Matching tolerance was 1 (week). Linear correlation between BP and other continuous variations were assessed by Pearson correlation analysis. Logistic regression analysis was performed with GH classified in a binary manner (presence / absence) as the dependent variable. Insulin therapy (categorized by whether or not) and other possible risk factors were entered into logistic regression analysis. Effect estimates are reported along with OR value, 95% CI and P value. The changes of BP after intervention (from the time of GDM diagnosis to one week before delivery) were subjected to paired sample test. Calculating difference of BP and comparing with student’s t test. All analyses were performed using SPSS 24.0 (IBM SPSS lnc, Chicago, IL, USA). Two - tailed P < 0.05 was considered to indicate statistical significance.