Maternal Obesity More Than Triples Child's T2D Risk

Liam Davenport

June 20, 2019

Children born to women who are overweight or obese have a significantly increased risk of developing type 2 diabetes later in life, the results of a large Scottish study reveal. The findings underline the need for effective weight loss intervention during and, ideally, before pregnancy.

Dr Rebecca Reynolds, British Heart Foundation Centre for Cardiovascular Science, University of Edinburgh, and colleagues crosslinked more than 118,000 births between 1950 and 2011 in Scotland to the national diabetes register.

They found that being overweight or obese during pregnancy was associated with an increased risk of the child developing diabetes, at 26% for overweight mothers and 83% for those who were obese.

However, when the researchers looked specifically at type 2 diabetes, they found that the risk was increased 39% for children born to overweight mothers, while the risk was increased a staggering 3.5-fold in those born to women who were obese.

'Profound Public Health Implications'

Worryingly, the results also showed that the proportion of women who were obese increased five-fold between the 1950s and the first decade of the 21st century.

The team said: "With the rising prevalence of being overweight/obese in women of childbearing age, our findings have profound public health implications.

"There is an urgent need to establish effective approaches to prevention of obesity and diabetes among mothers and their offspring."

The results, published by the journal Diabetologia on 19th June, follow previous research from Sweden showing that women who were obese in the first trimester of pregnancy were more likely to have a child with type 1 diabetes than other women.

The findings, in approximately 1.2 million children born in Sweden over a 14-year period, indicated that the risk was increased by 33%, although the association with obesity disappeared if either parent had type 1 or type 2 diabetes, both of which increased the risk of diabetes in offspring much more.

Clinician-Diagnosed Cases

Dr Reynolds explained that the current study is different because it was able to look at a longer lifespan among the offspring, so was able to pick up more cases of type 2 diabetes.

She also told Medscape News UK that the definition of diabetes used, as clinician-diagnosed, is stronger than that of self-reported diabetes.

Given the strength of the results, the question now becomes how to intervene to reduce levels of maternal obesity, with the timing of any intervention perhaps the most important aspect.

Dr Reynolds said: "There have been various studies that have looked at how to modify lifestyle and behaviour or give medication to women who are already pregnant and change the outcome of pregnancy, but they've been largely unsuccessful.

"That's why we really need to look preconception and help them prepare for a healthier pregnancy and achieve an ideal weight beforehand, rather than trying to modify something once you're already pregnant."

Dr Reynolds said, however, that identifying women before they conceive is a "challenge".

"One way is obviously to target women who've had an initial pregnancy and to look at women who are planning a second pregnancy, and then to raise awareness among young people that it's important to prepare well for pregnancy."

That may be easier said than done, however, as Dr Reynolds pointed out that "there's quite a lot of data showing that people spend more time preparing for going on holiday or going for a new job than they do for pregnancy".

She added: "The thing is that people maybe aren't aware of the risks of obesity in pregnancy.

"We need to raise awareness that pregnancy is a risky time for women; so the more healthy you are, the more likely you are to have a healthy outcome."

Expanding Evidence

While it is well known that maternal obesity is associated with short-term pregnancy complications such as gestational diabetes, pre-eclampsia, and large-for-gestational age infants, there is increasing evidence of longer-term health problems.

These include an increased risk in the offspring of premature cardiovascular disease and early mortality, which the researchers suggest may be mediated by an increased risk of type 2 diabetes.

To overcome some of the limitations of previous studies, they cross-linked a dataset of 118,201 mothers and their offspring from the Aberdeen Maternity and Neonatal Databank to the Scottish Care Information–Diabetes database.

The former contains all obstetric and fertility-related events, checked against National Health Service delivery records, in women from 1950 to the present day, while the latter was established in 2000 and contains demographic and clinical data related to diabetes care.

For the current analysis, the team looked at all women who had a live singleton infant delivered at term between 1950 and 2011 and who had their height and weight recorded at their first antenatal visit.

These were linked to a 2011 extract of the Scottish Care Information–Diabetes database to identify incident and prevalent type 1 and type 2 diabetes cases up to the start of 2012.

Study Findings

The overall prevalence of overweight and obesity was 24.8% and 9.5% respectively. Between 1950–1959 and 2000–2011, the prevalence obesity increased five-fold, from 3.1% to 15.7%.

Women who were obese were older than other women, had a higher parity and had a lower deprivation category. They were also more likely to have a history of diabetes or hypertension before pregnancy.

A record of diabetes diagnosis was identified for 0.6% of the offspring.

Compared with normal weight women, being overweight or obese was linked to a significantly increased risk of any diabetes in the offspring.

Taking into account maternal age at delivery, parity, deprivation category, maternal history of diabetes and offspring sex, the team calculated that overweight was associated with a hazard ratio of any diabetes in the offspring of 1.26 (p=0.009).

For women who were obese, the hazard ratio was even higher, at 1.83 (p<0.001).

Looking at specific forms of diabetes, the team found that 0.3% of offspring were diagnosed with type 1 diabetes, at between 1 and 52 years of age.

There was no significant association between maternal overweight or obesity and the hazard ratio of developing type 1 diabetes in both unadjusted and adjusted analyses.

Similarly, 0.3% of offspring were diagnosed with type 2 diabetes, at an age range of 10 to 61 years.

Unlike for type 1 diabetes, however, multivariate analysis taking into account all assessed covariates revealed that maternal obesity was associated with a significantly increased risk of type 2 diabetes in the offspring, at a hazard ratio of 3.48 (p<0.001).

Mothers who were overweight also had a significantly increased risk of having offspring who would go on to develop diabetes, at a hazard ratio of 1.39 (p=0.018).

The findings were unaffected by excluding women with diabetes before, during and after pregnancy.

However, differences were revealed when the team looked at sex differences, with a significant interaction between maternal weight and sex of the offspring in predicting any diabetes and type 2 diabetes.

The hazard ratios for any diabetes and type 2 diabetes in female offspring born to overweight mothers were 1.50 and 2.26, respectively, while in male offspring the hazard ratios were 1.11 and 1.11, respectively.

Pregnancy or Child's Lifestyle?

Approached for comment, Dr Judith Stephenson, Margaret Pyke professor of sexual & reproductive health at University College London, said that the study "adds to the body of evidence linking maternal obesity with diabetes in the children".

While praising its strong design and large dataset, she told Medscape News UK that "as it acknowledges, it still doesn't get round the issue of whether this is entirely due to what's going on in pregnancy or how much is as a result of the child's lifestyle later on".

However, Dr Stephenson noted that the authors make the point "that it's unlikely to be either/or, it's likely to be both things".

She added that, regardless of the exact underlying cause, "all this evidence keeps highlighting the importance of the mother's health during pregnancy and before pregnancy, that it's an important time to intervene".

Agreeing with Dr Reynolds, Dr Stephenson said that the pre-pregnancy period is key, as "trying to reverse obesity once a woman is pregnant is really pretty difficult".

However, she said that "we really haven't focused much on that preconception period for various reasons which I think are fairly self-evident".

She explained: "Women don't pop up saying: 'Hey, I'm planning a pregnancy'. They want to maybe keep it quiet until they're 12 weeks pregnant, when a lot of the biological mechanisms that get put in place around the time of conception have all happened, so it's all a bit late."

For Dr Stevenson, there is a need to find "sensitive and effective ways of delivering that message, to women in different groups and in different settings".

This could include developing an appropriate intervention for women who visit early pregnancy units following a miscarriage.

It would be an emotional time, however, and clinicians would want to avoid any implication that the miscarriage was related to their weight.

"Nonetheless, that I think is an opportunity for some appropriate health intervention because these women have time before they get pregnant again, and they may not know about the actions that they can take and the things they need to do."

She continued: "This is my own view, but it's an area of healthcare and a period in women's lives when we could really explore some better ways of supporting them to improve health for their pregnancy.

"Whilst I'm not saying that one shouldn't tackle those things in pregnancy, because you can get women to think differently about and maybe change their lifestyle a bit, but it's probably not going to reverse the metabolic problems within that pregnancy, and the implications for that child.

"But you might set up different patterns of nutrition and so on, which would mean that they have healthier meals and so on with the family and the babies," Dr Stephenson concluded.

This work was supported by Tommy's Centre for Maternal and Fetal Health and the Medical Research Council. We acknowledge the support of the British Heart Foundation.

Diabetologia 2019. doi: 10.1007/s00125-019-4891-4

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