Diabetes and Pregnancy

Abstract

Cover image: Mother and Child. Copyright © Fanitsa Petrou. All rights reserved. In this issue, we compile seven state-of-the-art reviews covering key basic and clinical science aspects of diabetes pregnancy. Worldwide, it is estimated that in 2013 there were 21.4 million live births complicated by hyperglycaemia, of which 16% had mothers with Type 1 or Type 2 diabetes and the remainder with hyperglycaemia in pregnancy (commonly referred to as gestational diabetes). Hartling et al. (p. 319) review the impact of various diagnostic criteria on infant health, while Professor David Hadden and I (p. 252) provocatively suggest that it is time move beyond these arbitrary cut-offs dichotomizing a continuous variable. We advocate replacing the inconsistent ‘gestational diabetes’ terminology with ‘hyperglycaemia in pregnancy’. Asia represents the continent with the largest number of people with diabetes, with up to one in four pregnancies being complicated by hyperglycaemia. Not surprisingly, this poses significant challenges for implementation of effective screening and treatment pathways, particularly in low-income countries. Tutino et al. (p. 302) remind us that South Asian women develop diabetes at lower BMI (mean BMI of mothers with hyperglycaemia in pregnancy in Vietnam of 21.1 kg/m2). They are particularly susceptible to the consequences of urbanization, with hyperglycaemia doubling from rural to urban regions, and vitamin B12 deficiency. Finer et al. (p. 263) elegantly describe how deficiencies of dietary micronutrients, including B vitamins, tetrahydrofolate and essential amino acids, could lead to disruption of the one-carbon cycle, with downstream metabolic consequences. Metformin can also exacerbate vitamin B12 deficiency and so the consequences of disrupted one-carbon cycling may extend beyond lacto-vegetarians and certainly warrant further study. Catalano and Kim highlight the lasting impact of pre-pregnancy BMI and retention of gestational weight gain. Kim (p. 292) cautions that women who gain excess weight during pregnancy retain 3 kg more than women within the US Institute of Medicine recommendations both at 3 years and at 15 years later. After a pregnancy complicated by hyperglycaemia, every 1-kg increase in pre-pregnancy weight is associated with a 40% increased odds of developing Type 2 diabetes. Catalano (p. 273) speculates whether inflammation is the primary mechanism relating to increased insulin resistance in pregnant women with obesity and hyperglycaemia. Supporting the physiological findings of Catalano, Lowe Jr. and Karban (p. 254) describe variants in six inflammatory pathway genes with evidence for association with maternal metabolic traits. Holt and Lambert (p. 282) tackle the burning clinical question of oral hypoglycaemic agents, providing reassurance regarding the safety, effectiveness and clinical acceptability of metformin. More data about potential placental transfer of glibenclamide are needed, with some studies suggesting increased infant macrocosomia and neonatal care admissions. Lowe Jr. and Karban (p. 254) updates us on the latest findings and potential future impact of high-throughput ‘omics’ technologies to identify genetic variation associated with maternal metabolic traits. While hyperglycaemia in pregnancy represents a significant impact on health resources, it also presents an exciting opportunity to intervene and reduce, delay or prevent subsequent problems for the mother and her children. We await with great interest data from ongoing interventions into the role of diet and lifestyle, oral hypoglycaemic agents, vitamin D, vitamin B12 and omega-3 polyunsaturated fatty acids.