A University of Auckland academic is behind a large study that has shown that women who get gestational diabetes are at a higher risk of getting type 2 diabetes, hypertension and ischaemic heart disease.

The study used a large United Kingdom primary care database that included 9,118 women diagnosed with gestational diabetes mellitus (GDM) between January 1990 and May 2016 and compared them with 37,281 women who were the same age and pregnant over a similar time period but did not develop GDM.

The research was carried out at the University of Birmingham, Institute of Applied Health Research, with Dr Krishnarajah Nirantharakumar as the lead investigator and Dr Barbara Daly as the lead author from the University of Auckland’s School of Nursing. Dr Daly now hopes a similar study can be conducted in New Zealand.

The study findings, “Gestational diabetes and cardiovascular disease”, have just been published in PLOS Medicine.

Gestational diabetes is increasing due to the obesity epidemic and increasing maternal age.

The study compared long-term cardiometabolic outcomes in women diagnosed with GDM with randomly matched pregnant control 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.

All records were for women who became pregnant between February 1990 and May 2016. Their mean age at the time of delivery was 33 years and ranged from 14 to 47 years. A significantly greater proportion of women with GDM compared with controls were economically deprived, overweight with a BMI of over 25, and had been diagnosed with hypertension.

“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 post-partum period,” Dr Daly says.

Of the women diagnosed with GDM, 280 (3.2 percent) developed hypertension and 14 (0.2 percent) ischaemic heart disease (IHD) compared with 1.3 percent and 0.06 percent of control women, respectively. 

“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 percent of women with GDM undergoing screening in the early post-partum period and had decreased to less than 40 percent by the second year.

“The guideline recommendations for screening and management of hypertension, lipids and smoking cessation are lacking and need to be reviewed.”

Dr Daly says guidelines need to be adapted to recommend annual screening for type 2 diabetes and for major cardiovascular risk factors such as smoking, hypertension, cholesterol levels and in physical activity. Clinical guidelines need to include post-partum screening and management of all cardiovascular risk factors in women diagnosed with GDM - not limited to type 2 diabetes.

This study is the first UK and the largest population-based study of women with GDM that utilized primary care records to report on incidence of cardiovascular disease without requiring a hospital admission. The findings add an important insight into the trajectory of the development of type 2 diabetes, hypertension and cardiovascular disease in the early and latter post-partum periods.

The findings are broadly consistent with the French study utilizing hospital records, Canadian study utilizing 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.”

The study findings, “Gestational diabetes and cardiovascular disease”, will be published at 8.00am Wednesday 17 January 2018 NZDT, in PLOS Medicine. Once published they can be viewed here: http://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1002488