The study compared long-term cardio-metabolic outcomes in women diagnosed with gestational diabetes mellitus (GDM) and randomly matched pregnant women not diagnosed with GDM using The Health Improvement Network (THIN), a large database of anonymised electronic medical records collected at primary care clinics throughout the UK.
The database included 9,118 women diagnosed with GDM between January 1990 and May 2016, and compared them with 37,281 expectant women of the same age group over a similar time period, but who did not develop the condition.
Their mean age at the time of delivery was 33 years, and ranged from 14 to 47 years. Compared to the controls, a significantly greater proportion of women with GDM were economically deprived, overweight with a BMI of above 25, and had been diagnosed with hypertension.
Of the women diagnosed with GDM, 280 (3.2%) developed hypertension and 14 (0.2%) ischaemic heart disease (IHD) compared with 1.3% and 0.06% of the controls, respectively.
"This was the first large population-based study in the UK that reports on the increased risk of cardiovascular disease in women diagnosed with GDM, and quantifies the high incidence of type 2 diabetes and hypertension in the postpartum period," said lead author Dr Barbara Daly, from the University of Auckland's School of Nursing.
"Women diagnosed with GDM were over 20 times more likely to develop type 2 diabetes, had almost twice the risk of developing hypertension, and were two-and-half times more likely to develop ischaemic heart disease following delivery, compared with control women.”
The increased risk persisted throughout the 25-year follow-up period. Follow-up screening for type 2 diabetes was poor, with less than 60% of women with GDM undergoing screening in the early postpartum period; this had dropped to under 40% by the second year.
Dr Daly said guidelines needed to be adapted to recommend annual screening for type 2 diabetes and major cardiovascular risk factors such as smoking, hypertension, cholesterol levels and physical inactivity.
Clinical guidelines must include postpartum screening and management of all cardiovascular risk factors in women diagnosed with GDM, and not limited to type 2 diabetes, she added.
The paper concluded: "Women diagnosed with GDM were at very high risk of developing type 2 diabetes and had a significantly increased incidence of hypertension and IHD.
"Identifying this group of women in general practice and targeting cardiovascular risk factors could improve long-term outcomes."
The findings are broadly consistent with the French study utilising hospital records, Canadian study utilising primary care records, and the US Nurses' Health Study using self-reported diagnosis of GDM. Because this is a new area of research, additional follow-up studies are required to further validate the current findings.
"It would be ideal to explore this relationship in New Zealand, given our high rates of GDM and cardiovascular disease," said Dr Daly.
Source: Plos Medicine
"Increased risk of ischemic heart disease, hypertension, and type 2 diabetes in women with previous gestational diabetes mellitus, a target group in general practice for preventive interventions: A population-based cohort study"
Authors: Barbara Daly, et al.