Overeating during pregnancy linked to maternal weight gain and child obesity

"How 'eating for two' during pregnancy is a major health risk: One-in-three women admit 'out-of-control' binges that make them pile on the pounds," is the headline from the Mail Online.

This follows a study of 11,132 women from the Avon region of England who were pregnant in the early 1990s. It looked at how often women said they'd experienced "loss of control over eating" (LOC) during pregnancy and whether this was linked to weight gain in the mothers and their babies.

Having a poor diet and being overweight before and during pregnancy are linked with diabetes during pregnancy (gestational diabetes) and heart disease in the mother. They may also affect the child's risk of becoming obese.

The study found that women who reported frequent LOC in pregnancy gained more weight during pregnancy than women who said they never experienced this loss of control.

Additionally, the children of women with frequent LOC were more likely to be overweight or obese at age 15 than children of mothers without loss of control.

As the study was observational, it's not possible to fully rule out the influence of other health and lifestyle factors that could have affected the mothers' and children's risk of weight gain. It may also be that health awareness has changed substantially since 1990-92, when the women in this study were pregnant.

Nevertheless, the study supports current healthy eating advice for pregnant women, which recommends eating a variety of foods but emphasises there is no need to "eat for two".

Where did the story come from?

The study was carried out by a team of researchers from several institutions in the UK, the US, Saudi Arabia and Switzerland, including University College London and the University of Geneva.

One of the authors was supported by an award from the National Institute for Health Research (NIHR) and a WellChild project grant, and the study was published in the peer-reviewed American Journal of Clinical Nutrition. The abstract is available to read online.

The Mail Online's coverage was generally accurate. However, while the study did find that approximately 35% of women had loss of control over eating during pregnancy, the Mail Online reported this statistic as if it was representative of the general population – but this was a study of women from the Avon region of England who were pregnant nearly 30 years ago, so we do not know to what extent the findings apply to all women 30 years later.

What kind of research was this?

This was a prospective cohort study investigating the impact of loss of control over eating during pregnancy on mothers and their babies.

LOC is described as a "subjective experience of feeling out of control when eating, irrespective of the amount consumed". Although reportedly common, LOC remains understudied in pregnancy.

Observational studies are a good way of looking at the relationship between factors – in this case, pregnancy diet and weight gain.

However, the data used came from another long-term study – designed to look at the effects of environment, genetics and other factors on health and development – that was not specifically set up to look into the question of maternal overeating. Therefore, it may not have fully accounted for all possible health and lifestyle factors that could have influenced the results.

What did the research involve?

The researchers analysed data on 11,132 women from the Avon Longitudinal Study of Parents and Children (ALSPAC). This study recruited 14,541 pregnant women living in Avon, England, who were expected to give birth between April 1 1991 and December 31 1992.

Only women who had completed a questionnaire at 32 weeks, which had questions on LOC, were included in this study.

At 32 weeks of pregnancy

When the women were 32 weeks pregnant, they were asked to report whether they had experienced loss of control over eating during their pregnancy. The choice of answers was:

• not at all
• yes, occasionally
• yes, most of the time

The researchers categorised their findings as frequent LOC, occasional LOC and no LOC.

Diet during pregnancy was assessed by food-frequency questionnaires that looked at consumption of a variety of food and drink. The researchers scored the different dietary patterns and assigned the following categories:

• health-conscious
• traditional
• processed
• snacking
• vegetarian

After the birth

Maternal weight gain during and after pregnancy was measured using medical records and via a questionnaire 8 weeks after the birth. The babies' weight was recorded at birth.

Those children still enrolled in the Avon study (5,515) when aged 15.5 had their weight and height measured.

In their analysis, the researchers took account of sociodemographic factors – based on maternal education, age and number of children – and pre-pregnancy weight and height.

Women with gestational diabetes were excluded from the analysis.

What were the basic results?

Overall, loss of control over eating in pregnancy was common, reported by 36.3% of women: 31.1% (3,466 women) reported only occasional LOC in pregnancy, while the remaining 5.2% (582 women) reported frequent LOC.

When compared with women without LOC, women with LOC reported higher total energy intake and eating more snacks. They also had lower levels of vitamins B and C, and folate.

Women with LOC were more likely to have higher-than-recommended weight gain in pregnancy than women with no LOC.

Women with frequent LOC had 3 times the risk of higher-than-recommended weight gain in pregnancy (odds ratio [OR] 3.41, 95% confidence interval [CI] 2.73 to 4.27). These women gained on average 3.74kg more during pregnancy than women with no LOC.

Those with occasional LOC had an almost-doubled risk of weight gain (OR 1.66, 95% CI 1.58 to 1.96).

Child birthweight was higher for women with frequent and occasional LOC in pregnancy (0.07kg and 0.04kg, respectively) than women with no LOC.

Children of mothers with frequent LOC in pregnancy were more likely to be overweight or obese at 15.5 years than children from mothers with no LOC (OR 2.02, 95% CI 1.37 to 3.01). There was no difference for women reporting occasional LOC.

How did the researchers interpret the results?

The researchers said: "Pregnancy LOC eating is common and has an adverse short- and long-term impact on mother and offspring, but has received very limited attention.

"Our findings further the understanding of risk factors for obesity and highlight a need for improved identification of maternal pregnancy loss of control eating."

Conclusion

This was an interesting study that looked specifically at the effects of loss of control over eating during pregnancy on mothers and their babies.

The findings that women with frequent LOC were more likely to have higher-than-recommended weight gain in pregnancy and that their children were more likely to be overweight or obese seem highly plausible.

However, the study had some limitations.

Although it was a large study, including more than 11,000 women, the main findings involved a much smaller subgroup who reported frequent LOC. Analyses involving smaller samples may be less reliable, so risk estimates may not be definite.

The food-frequency questionnaire was only filled out once during pregnancy. As with all self-reported data, there is the possibility of under- or over-reporting dietary intake.

The answers given may also not have been entirely accurate and may not have represented habits throughout pregnancy. In particular, a concept such as "loss of control of eating" is highly subjective and open to interpretation.

Although the researchers adjusted for some confounders, there may have been other factors at play, and the study cannot tell us LOC in pregnancy directly caused maternal weight gain or obesity in offspring. For example, it's highly likely the home environment, lifestyle and family diet influenced weight gain throughout childhood.

Finally, the women in the study were pregnant almost 30 years ago – health education, diet and lifestyle patterns have changed substantially since then.

Nevertheless, this study supports current diet and physical activity recommendations for pregnant women. Read more on having a healthy diet in pregnancy and exercise in pregnancy.