Exercise during pregnancy associated with decreased asthma risk in children

Key takeaways:

• Exercising three times weekly while pregnant decreased the risk for asthma in children.
• Prepregnancy exercise showed no effect on asthma development among children.

Maintaining regular physical activity during pregnancy appeared to be associated with decreased asthma risk during childhood, according to a study published in Med.

Lead study author Pirkka Kirjavainen, PhD, chief researcher at the Finnish National Institute of Health and Welfare and University of Eastern Finland, told Healio that the finding was accidental. 

Kirjavainen and colleagues were studying how obstetrical factors impact microbial exposures at birth and pediatric asthma development.

“When looking into potential confounders, we also tested the effect of exercise, as it theoretically could affect both the asthma development in child and microbial exposure at birth via effects on maternal microbiota. We thought it is a bit borderline whether or not it needs to be tested, but decided to include it just in case as it would be very interesting if there was an influence,” Kirjavainen said.

As expected, the study authors did not find a significant influence on microbial exposure; however, they were surprised to find a strong protective association with asthma.

“As such an association had not been previously reported, we thought it would be important to investigate whether it holds in a larger sample with thorough adjustments,” Kirjavainen said.

Study findings

Kirjavainen, Emma-Reetta Musakka, BM, MSc, doctoral researcher at the University of Eastern Finland, and colleagues assessed data on 963 mother-infant pairs from the prospective Kuopio Birth Cohort study. Data was taken from the Kuopio University Hospital birth registry as well as questionnaires about maternal physical activity during pregnancy, confounding factors and children’s asthma diagnosis by ages 5 to7 years.

Among the 963 mother-infant pairs, of which 49% of the infants were girls, the mean frequency of maternal exercise during pregnancy was 3.5 times a week (standard deviation [SD], 2.5).

Researchers found a positive association between this physical activity during pregnancy and maternal education, gestational weight gain, healthy eating habits, dog ownership and a child’s sports practice attendance.

Negative associations were found between physical activity during pregnancy and maternal age, BMI, previous deliveries, infections, stress and the child’s birth weight.

Mothers of infants who developed asthma had a lower mean frequency of exercise per week while pregnant compared with mothers of children who did not develop asthma (3.1 vs. 3.5). Of the 890 (93%) mothers that reported on the type of exercise they performed, the most common was walking (34%), jogging (32%), strength training (29%), and group classes or home workouts (22%).

Among the children, prevalence of asthma was higher in boys compared with girls (9% vs. 6%; P = .03). It was also more common when children had mothers or fathers with asthma (P = .02 and P < .01, respectively) and mothers who used oral antibiotics during pregnancy (P = .03). The authors called these findings expected.

When exercise frequency occurred less than three times vs. three times or more a week, the adjusted odds ratio for a child developing asthma was 0.54 (95% CI, 0.33-0.89; P = .02). Exercising three times a week was more common among mothers with a normal BMI compared with a high prepregnancy BMI (P < .01), mothers who had longer (15-16 years) vs. shorter (< 15 years) lengths of education (P = .05) and mothers whose child attended vs. did not attend sports practices (P = .01).

Pregnant mothers experiencing common colds (P = .03), other infections (P < .01) and previous deliveries (P < .01) were more likely to engage in exercise less than three times a week. Pregnant mothers with healthy nutrition (P < .01), daily vegetable intake (P < .01) and dog ownership (P = .02) reported exercising at least three times a week.

Researchers noted prepregnancy exercise has weaker associations on asthma development compared with exercise during pregnancy.

Study impact

“The strength of the findings and stability across multitude of potential confounders was somewhat surprising,” Musakka told Healio. “It is noteworthy, that the preventive impact of adequate maternal exercise during pregnancy was comparable in strength to avoiding parental smoking during pregnancy.”

There are very few means for asthma prevention, and avoidance of exposure to smoking is among the best known and efficient. Considering the strength of the association, it was also somewhat surprising that the association between maternal exercise during pregnancy and child’s asthma was not previously reported.”

Musakka further explained that maternal exercise is negatively associated with factors known to associate with raising a child’s asthma risk, such as BMI, smoking, socioeconomic status and stress, and many would assume these to explain the protective association. However, the association between maternal exercise and reduced asthma risk in children, was independent of these risk factors.

Kirjavainen emphasized that this study can provide an additional way to prevent asthma. The findings could be used to further encourage pregnant women to avoid inactivity and follow the current recommendations for exercise during pregnancy.

Pirkka Kirjavainen

“Our findings show that exercising only three times per week reduced the risk of child's asthma,” he said. “This knowledge can help clinicians encourage patients to engage in moderate physical activity and adopt healthier lifestyle habits.”

Although exercising more than three times a week did not increase the benefits, the authors said the intensity and frequency needs further study.

“Replication of the association would also be called for, as well as studies into the mechanisms of this observation, which could also result in innovations facilitating the development of additional preventive strategies,” Kirjavainen said.

“Our findings are well in line with current health recommendations but do suggest to further endorse the importance of active lifestyle throughout the life, also during pregnancy,” Musakka said.

References:

• Maternal exercise during pregnancy may protect the child against asthma. https://www.uef.fi/en/article/maternal-exercise-during-pregnancy-may-protect-the-child-against-asthma. Published Oct. 10, 2024. Accessed Oct. 21, 2024.

For more information:

Pirkka Kirjavainen, PhD, can be reached at pirkka.kirjavainen@uef.fi

Emma-Reetta Musakka, BM, MSc, can be reached at emma-reetta.musakka@uef.fi