Mwenya Mubanga, MD, PhD

Credit: Karolinska Institutet

Maternal overweight and obesity during pregnancy is linked to higher risk of offspring asthma, according to new findings, but associations with food allergy are likely confounded due to familial factors.¹

These findings came from a research letter in which associations between body mass index (BMI), food allergies, and offspring asthma were assessed by investigators, given that maternal obesity has been known to be a risk factor which can impact fetal programming as well as early childhood health.²

The research was authored by Mwenya Mubanga, MD, PhD, from the Department of Medical Epidemiology and Biostatistics at the Karolinska Institutet in Sweden.

“However, studies report inconsistent associations between maternal BMI and asthma and FA, and potential confounding from shared familial factors remains uncertain,” Mubanga and colleagues wrote. “We investigated the association between maternal body mass index (BMI) and offspring asthma and FA in a population-based study with a sibling sub-population analysis.”

Background and Findings

The investigators’ study involved a cohort of 1,389,842 Swedish children who were born between 2006 and 2019, whose data were obtained from the Swedish Medical Birth Register. The team followed these children until December 2021 to assess the occurrence of asthma and food allergy.

Asthma was identified using specific diagnostic codes or medication records, while food allergy was assessed by the investigators based on physician-confirmed IgE-mediated codes or based on adrenaline medication usage.

The investigators calculated maternal BMI based on measurements taken during antenatal booking and classified into four categories: underweight (BMI < 18.5), overweight (25 ≤ BMI < 30), healthy weight (18.5 ≤ BMI < 25), and obese (≥ 30). In additional analyses, the team treated BMI as a continuous variable.

The research team examined the relationships between maternal BMI and offspring asthma and food allergy using a Cox proportional hazards regression, with attained age being used as the analysis timescale.

To account for potential changes over time, the team divided the follow-up period into two intervals: <3 years and ≥3 years. All statistical analyses were conducted through the use of STATA 16.

Overall, out of the 1,389,842 children included in the investigators’ study, 10.3% were shown to have developed asthma. The team reported that maternal overweight and obesity were linked to a higher risk of asthma in offspring, both for children under 3 years old (adjusted hazard ratio [adj-HR] 1.15 and 1.35, respectively) and those aged 3 years or older (adj-HR 1.09 and 1.24, respectively).

However, for food allergy in children aged 3 years or older, the research team noted that maternal overweight and obesity were linked with a lower hazard ratio. In sibling control analysis, the team added that the associations remained substantial for asthma, both prior to and after turning 3 years of age, for maternal obesity.

They added that the associations were found not to have persisted for allergy to foods. Similarly, when considering maternal pregnancy BMI as a continuous factor, higher BMI was found to be linked to an increased risk of asthma and a decreased risk of any food allergy in children under 3 years.

For those aged 3 years or older, the investigators reported that higher BMI was linked with an increased hazard of asthma and a lower hazard of any allergy to food. In the sibling analyses, only the estimates for asthma remained significant.

Similar findings were observed in a study from Denmark (n=38,874), in which the investigators noted that maternal BMI was associated with greater risk of asthma/wheezing. Another American study found that higher pre-pregnancy BMI was associated with a greater risk of food allergy in middle childhood but not for early childhood.

Additionally, the research team noted that familial confounding may have different effects on the associations between food allergies and maternal obesity compared to maternal obesity and asthma.

“Limitations to our study include an inability to adjust for maternal FA or diet,” they wrote. “However, strengths include a large population, the use of multiple definitions for FA and our ability to conduct a sibling analysis which controls for some familial confounding.”

References

1. ^{Mubanga, M., Brew, B.H., Karim, H., Curman, P., Hedman, A., Lundholm, C. and Almqvist, C. (2023), Maternal body mass index in pregnancy and offspring asthma and food allergy. Allergy. https://doi.org/10.1111/all.15803.}
2. ^{Leddy MA, Power ML, Schulkin J. The impact of maternal obesity on maternal and fetal health. Rev Obstet Gynecol. 2008; 1(4): 170- 178.}