Exercise as it relates to Disease/Physical health of children resultant to prenatal exercise

This page is a critique of the article Body mass index and physical activity in seven-year-old children whose mothers exercised during pregnancy: follow-up of a multicentre randomised controlled trial which was published in BMC Paediatrics 2021 November 8. The article was authored by Bjøntegaard KA, Stafne SN, Mørkved S, Salvesen KÅ and Evensen KAI.

What is the background to this research

Prenatal overweightness and obesity is a growing issue. According to the Australian Institute of Health and Welfare (2022) the prevalence increased from 45.8% in 2015 to 49.9% in 2020. Prenatal overweightness and obesity is linked to multiple health issues such as diabetes, cardiovascular disease, and birth complications. Prenatal overweightness and obesity is a common determinant for childhood overweightness and obesity, and associated illnesses. Fuemmeler et al (2013) found a direct correlation between parental and childhood obesity. This study aims to fill a gap in existing literature, by attempting to answer the question "what effect does structured exercise during pregnancy have on childhood weight and physical activity on a long-term basis?"

The article Body mass index and physical activity in seven-year-old children whose mothers exercised during pregnancy: follow-up of a multicentre randomised controlled trial, follows up on a randomised control trial conducted by the Norwegian University of Science and Technology in conjunction with Saint Olavs Hospital, Trondheim University Hospital, and Stavanger University Hospital.

The aim of the study was to determine if women engaging in a structured exercise intervention during pregnancy would affect the Body Mass Index (BMI) and physical activity of their children at seven years old. The researchers hypothesised there would be no significant intergroup difference in the childrens BMI or physical activity levels. They also theorised the childrens BMI and physical activity levels would correlate to their mothers. Previous research has established the safety of exercise during pregnancy, the response to exercise by pregnant women, and the link between mothers living a healthy lifestyle and their children doing the same. There is currently limited research linking potential responses to prenatal pregnancy and long-term childhood health outcomes.

Where is the research from

This research was conducted by the Norwegian University of Science and Technology in conjunction with Saint Olavs Hospital, Trondheim University Hospital, and Stavanger University Hospital. The primary author, Bjøntegaard KA was a student at the university. The co-authors of the paper, Stafne SN, Mørkved S, Salvesen KÅ, and Evensen KAI are well published and cited academics from the universities department of public health, with a combined 312 publications and 8,821 citations.

What kind of research was this

This paper is based on a seven year follow-up on a randomised control trial. A randomised control trial is considered to be the gold standard of study formatting for the purpose of testing intervention efficacy.

The initial subjects selected for the study were heavily screened for any potential contraindications to exercise. In order to narrow the scope of the study and have as many controls as possible, only Caucasian women over eighteen with a single foetus were eligible. The study was not blind as the researchers considered this too risky for the subjects should complications arise.

The purpose of the initial trial was to determine the effect of prenatal exercise on gestational diabetes, the data was used in conjunction with the data obtained in the seven year follow-up to produce this study.

What did the research involve

The study recruited 875 women who were between 18-22 weeks of pregnancy. Women were recruited into the study whilst attending hospital for their initial ultrasound. These women were randomly assigned to the control or intervention group. The control group received standard prenatal care, and were not instructed to stop exercise. The intervention group were given a twelve-week structured exercise program.

The women were assessed upon commencement, at the end of the trial, and three months postpartum. The children were assessed at eighteen months and seven years. Participant data collected included height and weight in SI units, socio-economic status, and number of exercise sessions/week. At the baseline assessment participants were asked about familial diabetes status, and birth weight of any previous children. The seven year follow-up was done via self-reporting. At the follow-up, the childrens BMI, physical activity levels, and health/disease status were recorded. Exclusion criteria included high-risk pregnancies, contraindications to exercise prescription, and residing more than 30 minutes from the hospital. Most participants had a healthy BMI with a mean of 24.45. All exercise was prescribed by qualified allied health professionals.

There was a lower response to the seven year follow-up (66% of the initial participants) than the researchers hoped for, which they acknowledge may have affected the outcomes. The data of the seven year follow-up being self-reported presents a continuity problem. The initial data and follow-up at eighteen months were conducted by clinicians in a hospital using verifiable measurement techniques. Self-reported data collected in health studies is subject to participants under- or over-reporting data to meet perceived expectations.

What were the basic results

The study concluded there was no intergroup difference at the seven year follow-up. The study demonstrated BMI and physical activity correlated between mother and child. The data showed women in both groups engaged in near-identical amounts of physical activity; this contributed to the lack of significant intergroup difference.

The researchers acknowledged the limitations of the data and stated all interpretations of results should be done with caution.

What conclusions can we take from this research

The conclusion aligned with the researchers' hypothesis; there was correlation between the BMI and physical activity of the mothers and their children at the seven year follow-up. There was no significant evidence of intergroup difference, attributed to the homogenous nature of the participants. Women in both groups regularly exercised and had healthy a BMI pre-study.

The key conclusion from this study is maintaining healthy BMI and achieving adequate physical activity during both prenatal and postpartum phases of pregnancy is likely to result in children with a healthy BMI who engage in sufficient physical activity.

The limited population of this study minimises any practical inferences. Further studies are required to determine if this intervention would provide similar results in ethnically diverse or rural populations. The majority of subjects entered into the study with a healthy BMI. Further studies are required to determine if this intervention style would yield benefit to overweight/obese prenatal women.

Practical advice

• Exercise is safe for otherwise healthy pregnant women.
• Pregnancy offers a chance to engage in healthy new habits.
• Pregnant women should aim to be active most, if not all, days of the week.
• During pregnancy, women should aim for 2.5-5 hours/week of moderate intensity exercise.
• Moderate intensity exercise should feel challenging, but you should be able to maintain conversation.
• Leading an active lifestyle is beneficial for mothers and children, both prenatal and postpartum.
• If you have any concerns around exercise, or don't know where to start, consult your GP or an accredited exercise physiologist.

Further information/resources

Explore the Department of Health Physical Activity Guidelines for inspirational ideas on how to exercise.

Find an Accredited Exercise Physiologist to help you on your journey.

See what the American College of Obstetrics and Gynaecology says about exercise during pregnancy.