Complications
Maternal hypertension frequently complicates gestational diabetes mellitus (GDM). Regular monitoring of blood pressure and urinary protein is warranted.[23] The risk of pre-eclampsia is also higher in GDM and rises with higher maternal glucose levels.
Treatment of GDM may help reduce the risk of pre-eclampsia and other hypertensive disorders of pregnancy.[68][69]
Non-elective caesarean section rates are increased in women with gestational diabetes mellitus (GDM), only partly explained by fetal macrosomia.[127][23] Awareness of a patient's GDM status may influence delivery planning and increase caesarean rates because of concerns about macrosomia and other fetal complications.
Risk increases with poor maternal glucose control.[68]
Risk of hypoglycaemia increases with degree of maternal hyperglycaemia, especially during labour. In a case-control study, hypoglycaemia occurred in 5% of neonates born to mothers with gestational diabetes mellitus (GDM), compared with less than 1% of controls.[25] Careful intrapartum glycaemic monitoring and control are therefore warranted.
Neonatal polycythaemia occurs in 10% to 20% of pregnancies complicated by diabetes, a prevalence three- to fourfold higher than in pregnancies without diabetes.[25]
Gestational diabetes mellitus (GDM) increases risk of hyperbilirubinaemia to approximately 17%, approximately twice the rate observed in controls.[25]
Hypocalcaemia has been documented in almost 5% of pregnancies complicated by gestational diabetes mellitus (GDM), a rate about double that of controls without diabetes.[25]
Pregnancies of women with fasting hyperglycaemia and poor glycaemic control carry a higher risk.[128] In contrast, the risk is unlikely to be increased in women with gestational diabetes mellitus (GDM) that is well controlled with diet alone. In one randomised trial, treatment of GDM significantly reduced the risk of serious perinatal complications, including fetal demise.[129]
A meta-analysis involving over 5 million women and more than 100,000 events found that individuals with gestational diabetes mellitus (GDM) had a 2-fold higher risk of future CVD events within the first decade postpartum.[130] This association was not solely explained by type 2 diabetes, as even after excluding women who developed type 2 diabetes, GDM was linked to more than a 1.5-fold higher risk of CVD.[130] Another meta-analysis found that GDM was associated with increased risks of both overall and type-specific (coronary artery disease, myocardial infarction, heart failure, angina pectoris, cardiovascular procedures, stroke, and ischaemic stroke) cardiovascular and cerebrovascular disease, independent of conventional CVD risk factors or subsequent diabetes.[131] The increased risk of CVD associated with GDM may be partly due to the clustering of other risk factors such as overweight/obesity, dyslipidaemia, and hypertension.[73] Emerging epidemiological evidence suggests a role for coronary calcium scoring to identify subclinical CVD in women with prior GDM, although the optimal frequency of CVD risk factor screening and the most appropriate diagnostic tests (e.g. laboratory and/or imaging markers) in the postpartum period remain to be determined.[73]
In utero exposure to gestational diabetes mellitus (GDM) increases the risk of glucose intolerance, overweight or obesity, metabolic syndrome, and elevated blood pressure in offspring later in life.[24] The Hyperglycemia and Adverse Pregnancy Outcome (HAPO) follow-up study, which evaluated nearly 5000 offspring at a mean of 11.4 years postpartum, found that the prevalence of obesity was significantly higher in children of women with GDM (diagnosed at 28 weeks of pregnancy) compared with those without, with an adjusted odds ratio of 1·58 (95% CI 1.24 to 2.01).[118] The HAPO study also demonstrated a continuous, independent association between maternal glucose concentrations during pregnancy and greater adiposity and impaired glucose tolerance risk in the offspring.[132][133] It further highlighted maternal weight status in pregnancy as a strong predictor of childhood excess adiposity, confirming findings from other observational studies.[24][134] The intergenerational risk of excess adiposity and dysglycaemia may be explained by shared genetics, shared familial environment, or by fetal programming resulting from the intrauterine metabolic environment created by excess maternal glucose.[24] It remains unclear whether treatment of GDM can reduce the long-term risk of metabolic complications in offspring.[24]
Hypoglycaemia is a common complication in insulin-treated patients and is usually mild in severity..[122]
Advise any woman who is taking insulin about the risks of hypoglycaemia and impaired awareness of hypoglycaemia during pregnancy.[4] Pregnant women taking insulin should always have a fast-acting form of glucose available (e.g., dextrose tablets or glucose-containing drinks).
Gestational diabetes mellitus (GDM) recurs in 30% to 84% of subsequent pregnancies.[17] The wide range in recurrence rate is influenced by the variability of formal retesting in subsequent pregnancies.
Gestational glucose intolerance, including conditions not meeting the definition of gestational diabetes mellitus (GDM), confers a high risk of future type 2 diabetes.[123] The majority of women with GDM eventually develop type 2 diabetes, but diabetes can be delayed through lifestyle modification or metformin treatment.[116][120][121][124][125] Women with prior GDM should be counselled about healthy lifestyle measures and require close monitoring for the development of type 2 diabetes.[3][126] UK National Institute for Health and Care Excellence (NICE) guidelines recommend annual screening with haemoglobin A1c (HbA1c) or fasting glucose.[4] The American Diabetes Association recommends screening every 1-3 years.[3]
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