Are working mums' children fatter?

“Working mums' kids are fatter and lazier,” is the headline in the Daily Mirror today. The newspaper reported on a survey of 12,000 schoolchildren. It said the survey found that children of mothers who worked were more likely to have habits that could lead to weight problems.

These included snacking on unhealthy foods, watching TV or playing on a computer for at least two hours a day, and being driven to school rather than walking or cycling.

This study’s findings are difficult to interpret, and do not necessarily mean that working mothers are the main cause or predictor of unhealthy behaviours in children. Children’s behaviour is likely to be affected by a wide range of factors, and although the researchers took some of these into account, they are likely to be connected (e.g. whether or not a woman works and her socioeconomic status).

The researchers note that other studies have not found a consistent relationship between maternal employment and children’s dietary and TV viewing habits.

Where did the story come from?

Dr S Sherburne Hawkins and colleagues from the UCL Institute of Child Health carried out this research. The study was funded by the Economic and Social Research Council and a consortium of government funders. It was published in the peer-reviewed Journal of Epidemiology and Community Health .

What kind of scientific study was this?

This was a prospective cohort study called the UK Millennium Cohort Study. The current publication investigated potential associations between maternal employment and childhood behaviours that may contribute to obesity.

The researchers recruited children born in the UK between 2000 and 2002. Families eligible for Child Benefit and living in the UK when their child was aged nine months were invited to participate. Of the 18,553 families asked, 72% agreed to participate.

The families were contacted again when the children were aged three and five years. Mothers reported on their employment status and working pattern at the start of the study and at the two follow-up points. This included whether they worked full or part-time, their hours, and any flexible working arrangements they had (for example, job sharing or working from home occasionally).

Women who reported not working at any of these three time points were classed as never working.

The mothers also gave information about various aspects of their child’s diet and physical activity or inactivity at age five. This included what type of snacks the child mostly ate, what types of drinks they drank between meals, how many portions of fruit (fresh, frozen or dried) the child ate each day.

The mothers were asked how many hours a day the child spent watching TV or using a computer (including games), how many days a week the child took part in a club or class involving physical activity, and how they travelled to school.

Families where the mother had not completed any of the questionnaires were excluded, as were cases where there were two children recruited from the same family or the main respondent had missing or implausible work data. Full data on these assessments were available for 12,576 children.

Childcare arrangements were assessed from nine months to three years of age. Children were classified as being in informal childcare, formal childcare, or cared for by a parent. Other information such as socioeconomic status was collected, but the methods used to do this were not reported in the abstract.

At age three, the children’s height and weight were measured and their body mass index (BMI) calculated. Criteria from the International Obesity Task Force were used to classify which children were overweight or obese.

Data were analysed for 12,576 children, and the researchers looked for relationships between maternal working patterns and their child’s health behaviours. The researchers took into account factors that could affect outcomes (potential confounders), such as ethnicity, socioeconomic status, highest maternal educational attainment, whether they were lone parents, and their age at the birth of the enrolled child. These factors were assessed at the start of the study.

The number of children the woman had at the last follow-up point was also included as a confounder.

What were the results of the study?

Almost a third (30%) of mothers had not worked since the birth of their child. Women who were employed worked an average (median) of 21 hours a week for 45 months. At age five, many children had behaviours that could promote excess weight gain: 37% of children primarily ate crisps or sweets as snacks, 41% primarily drank sweetened beverages between meals, and 61% used the TV or computer for at least two hours daily.

Children whose mothers had worked during the study were compared with children whose mothers had not worked. Children whose mothers worked full or part-time were more likely to eat fruit or vegetables between meals than other snacks, to eat three or more portions of fruit a day, to take part in organised exercise on three or more days a week, and to be driven to school.

In addition, children whose mothers worked full or part-time were less likely to snack on crisps or sweets between meals.

However, taking into account factors that could affect the results (such as ethnicity, socioeconomic status, highest maternal educational attainment, whether they were lone parents, their age at the birth of the enrolled child, and number of children in the household) reversed many of these relationships.

These adjusted analyses showed that children whose mothers worked full or part-time were more likely to drink mainly sweetened beverages between meals and to use the TV or computer for at least two hours a day. Children whose mothers worked 21 hours or more a week were less likely to eat fruit or vegetables between meals than other snacks, and less likely to eat three or more portions of fruit per day.

The relationship with being driven to school remained the same, with children whose mothers worked full or part-time being more likely to be driven to school.

There was no significant difference in consumption of crisps and sweets between meals between children whose mothers worked and those who did not.

What interpretations did the researchers draw from these results?

The researchers concluded that “after adjustment for sociodemographic characteristics, children
whose mothers were employed were more likely to have poor dietary habits, engage in more sedentary activity and be driven to school than children whose mothers had never been employed.”

What does the NHS Knowledge Service make of this study?

The results of this study are difficult to interpret because the relationship between maternal working and healthy behaviours was positive before adjustment for potential confounders, but then in some cases became negative after adjustment for these confounders. This could be because the factors that were assessed and adjusted for are likely to be interrelated, e.g. whether or not a woman works and her socioeconomic status. There are some other points to consider:

• The researchers only asked questions about employment at three time points, and this may not accurately reflect the women’s work status over the entire five-year period.
• The differences seen may not have been related to maternal working status but to some other factor that differed between the groups. To reduce the likelihood of this the researchers took into account a variety of factors, but unmeasured factors could still be having an effect.
• The questionnaire asked simple questions about specific aspects of the child’s diet and activities, and may not have captured a complete picture of their overall health.
• The reliability of the results depends on the accuracy of maternal reports of children’s behaviour. The researchers suggested that future studies could, for example, use objective measurements of children’s activity levels.
• The study did not assess paternal working, and therefore the effects of this are unknown. The study also did not assess parental health behaviours, which are likely to have an effect.
• The individual behaviours assessed do not by themselves indicate that a child is unhealthy or not, or indicate their overall balance of health behaviours. For example, children who are driven to school may eat a lot of fruit or participate in a lot of sport.
• The researchers note that other research has found no consistent relationships between maternal employment and children’s dietary and TV viewing habits.