Type 2 diabetes

Fetal macrosomia

Biology

Gestation

Endocrinology

Birth weight

Preeclampsia

Genetics

Pediatrics

Gestational diabetes

Gestational age

Obstetrics

Glycated hemoglobin

Medicine

Small for gestational age

Glycated haemoglobin

Shoulder dystocia

Pregnancy

Diabetes mellitus

Journal of Obstetrics and Gynaecology Canada

Objective This review sought to examine the association of HbA1c levels <6.5% in early pregnancy with the subsequent development of gestational diabetes mellitus (GDM) and adverse pregnancy outcomes. Methods A search of Medline and EMBASE was conducted for the period of January 1, 2000 to July 9, 2019 and the terms: “gestational diabetes or pregnancy diabetes mellitus” and “glycosylated hemoglobin or glycated hemoglobin A” and “pregnancy trimester, first, or first-trimester pregnancy,” “screening or prenatal screening,” “prenatal diagnosis or early diagnosis or prediction,” “retrospective studies or prospective studies.” Quality of evidence was assessed using the Newcastle-Ottawa scale. Inclusion criteria were: measurement of HbA1c <20 weeks gestation, the absence of pre-gestational diabetes mellitus, and analysis of HbA1c levels below 6.5%. The primary outcome evaluated was the development of GDM. Secondary outcomes were adverse pregnancy outcomes, including large-for-gestational-age birth weight, macrosomia, preterm birth, neonatal and perinatal death, congenital anomaly, preeclampsia, shoulder dystocia, and cesarean section. Results We screened 121 relevant abstracts. Thirty-two studies qualified for a full review, of which 11 met the eligibility criteria. All studies were assessed as high quality and found an increased risk of GDM with HbA1c levels >5.7. Levels >6.0 identified all patients who developed GDM. Adverse pregnancy outcomes were associated with elevated HbA1c levels in 4 of 6 studies and included preeclampsia, induced labour, shoulder dystocia, cesarean section, large-for-gestational-age birth weight, macrosomia, congenital anomalies, and perinatal death. Two studies found no association with adverse events. Conclusion HbA1c levels between 5.7% and 6.4% in early pregnancy consistently identified patients who went on to develop GMD. The evidence that particular levels are associated with adverse outcomes is less robust.

Early Gestational Diabetes Mellitus Screening With Glycated Hemoglobin: A Systematic Review