Gestational diabetes and adverse pregnancy outcomes : role of HbA1c, Anemia and other risk factors
Inas Adnan Hasan Saleh
إيناس عدنان حسن صالح
Background- Some women experience health problems during pregnancy such as gestational diabetes mellitus (GDM) and iron deficiency anemia. These complications can affect the health of the mother and fetus. Getting early detection can decrease the risk of adverse pregnancy outcomes. It has been reported that on average, 2-6% of pregnant women develop temporary GDM. Glycated hemoglobin (HbA1c) which is used to diagnose diabetes mellitus is not used for diagnosing GDM and the gold standard for diagnosis is still the oral glucose tolerance test (OGTT). Aims- To evaluate the role of HbA1c in screening and diagnosing GDM and its correlation with adverse pregnancy outcomes and assess its levels during and after pregnancy in the high-risk pregnant women to develop GDM. Among the risk factors, iron deficiency anemia and its correlation with adverse pregnancy outcomes will also be evaluated. Settings and design- Prospective study in prenatal care units of the United Nations Relief and Works Agency for Palestine Refugees in the West Bank (UNRWA). Methods- Data was collected by a structured questionnaire including age, gravidity, parity, BMI (Body Mass Index), family history for Diabetes Mellitus, and personal history of previous GDM. Blood pressure was taken on every visit. HbA1c, FPG (Fasting Plasma Glucose), and CBC (Complete Blood Cell count) were measured for all subjects, while 2 hour oral glucose tolerance test (OGTT) was done when required. GDM was diagnosed at pregnancy weeks 4-22 and 24-37 by the WHO (World Health Organization) criteria from 1999 as FPG ≥ 126 mg/dl or plasma glucose ≥ 140 mg/dl 2 hours after ingestion 75g glucose orally (OGTT), and the International Association of Diabetes and Pregnancy Study Groups (IADPSG) (FPG ≥ 92 mg/dl or plasma glucose ≥ 153 mg/dl 2 hours after the glucose load). A total of 955 pregnant women participated in this study. Statistical Analysis- Data was collected and analyzed using SPSS software version 23. Comparisons of the means, correlations and calculation of sensitivities and specificities for viii diagnosing GDM by HbA1c and the prediction of adverse pregnancy outcomes were performed. Results: Accumulated GDM percentage was 7.4% by WHO1999 criteria, and 45.8% by modified IADPSG criteria. The mean HbA1c1 value (HbA1c measured at first visit) in women with GDM1-WHO was significantly higher than women without GDM1-WHO (5.9 ± 0.6% compare to 5.4 ±0.4%, P = 0.000). In the same direction, a statistically significant difference was detected in the mean value of HbA1c1 between women who developed T2DM after delivery and those who didn’t (5.9 ± 0.5% compare to 5.4 ± 0.4%, P = 0.000). A positive correlation was observed between a baby’s birth weight and the baby’s head circumference and HbA1c1 at first visit. The optimal HbA1c1 threshold value at first visit for detecting GDM1-WHO was 5.75% with sensitivity 57.5% and specificity 85.1%. The HbA1c1 cutoff value ≥ 5.65% had a sensitivity of 31.1 % and specificity of 88.5% in detecting adverse pregnancy outcomes. A significant relationship was observed between pre-abortion and GDM1-WHO (P = 0.001), 64.5% of participant who previously complained from abortion were at risk to develop GDM. Four hundred and nine (43.6%) of the study population suffered from different adverse pregnancy outcomes, including abortion, perinatal death, having macrosomic babies, and cesarean delivery. The mean value of HbA1c1 (HbA1c measured at first visit) in women with adverse pregnancy outcomes was significantly higher than women without adverse effect (5.5 ± 0.44% compared to 5.3 ± 0.4%, respectively), as well as FPG1 (88.7 ± 10.8 compared to 86.1 ± 9.4) and OGTT1 (measured at first visit ) (107 ± 27.5 compared to 101 ± 22.8), respectively. A statistically significant difference was observed in the mean value of baby birth weight between GDM-IADPSG diagnosed and non-diagnosed at first and second visit, while baby birth weight was higher in GDM-WHO women diagnosed at the first and second visit but not statistically significant. Serum ferritin concentration in GDM1-WHO women was (36.8 ± 24 μg/dL), in GDM1-IADPSG, it was (28 ± 21.6 μg /L) and in DM women diagnosed at first visit by IADPSG was (31.7 ± 24.3 μg /L) that were higher than those who didn’t develop GDM1 or DM but not statistically significant. The percentage of anemia in the study population at first visit was 13.8% according to WHO definition (hemoglobin < 11g/dL), 25.3% had IDA (Iron Deficiency Anemia) ix according to WHO definition (serum ferritin < 12 μg /L), and the percentage of anemia at the second visit was 22.8% according to WHO definition (hemoglobin < 10.5g/dL at the second visit). 21.8% suffered from adverse outcomes related to anemia (baby birth weight < 2500g and preterm delivery < 37 gestational weeks) which were statistically significant with mean hemoglobin concentration at first visit (P = 0.033). Conclusions- HbA1c level in early pregnancy is increased in GDM, however, it does not replace OGTT for diagnosing GDM. However, including HbA1c as part of the diagnostic criteria for diabetes during pregnancy in 2010 by IADPSG was important which is still not adopted in Palestine. HbA1c level was associated with various adverse pregnancy outcomes in high risk women. Anemia in early pregnancy was associated with preterm delivery and low birth weight baby. Serum ferritin level in early pregnancy was higher in GDM women in comparison to non-GDM women, but it was not statistically significant. Keywords- HbA1c, GDM, OGTT, Ferritin, and adverse pregnancy outcomes.