Lower Pregnancy BMI, Increased Antibiotics May Contribute To Allergic Sensitization

Lower maternal pregnancy body mass index (BMI) and intrapartum antibiotic treatment have both been shown to increase risk of allergic sensitization in children, according to a recent study.

The prevalence of allergic diseases has been increasing since around the early 20th century, with determinants favoring the allergic phenotype being small family size, sex, smoking, breastfeeding duration, genetic factors and living in less rural environments. The urbanization of society, dietary changes, and newer hygienic conditions have contributed to changes in human lifestyle, and consequently to allergic sensitivity, explained study author Reetta Puisto MD, of the Department of Pediatrics and Faculty of Medicine at University of Turku in Finland, and colleagues.

Today, antibiotics are also frequently used from an early age, with 40% of all neonates exposed to intrapartum antibiotics. This rise in use, the urbanization of society, and modern trends in lifestyle and environmental exposures may have contributed to recent increases in allergic sensitization. The combination of risk factors known to predispose children to allergic diseases, along with antibiotic prevalence and lifestyle trends in the modern world, were the factors motivating Puisto and colleagues’ study.

“Today’s mothers are more often obese, giving birth at an older age and more frequently by caesarean section; this worldwide trend seems to continue,” they wrote. “In modern medicine, antibiotics are used abundantly from early life without fully understanding the long-term effects.”

Research And Methods

Investigators used a nested case-control trial design, based on 3 ongoing probiotic intervention trials aimed at reducing atopic disease risk. A total of 656 families contributed to the original studies, of which 433 children were chosen for the study based on inclusion criteria such as being born to mothers with asthma, atopic dermatitis, hay fever, food allergy, or allergic sensitization. This was done in order to aim the study at children with genetic predispositions.

The study’s primarily clinical endpoints were allergic manifestations within the study population in the first 2 years of life. Information on known risk factors for allergic diseases were gathered from prospectively collected study records for the research, with the factors being:

• Child’s sex
• Having older siblings
• Maternal smoking during pregnancy
• Breastfeeding duration
• Maternal prepregnancy BMI
• Mode of delivery
• Maternal intrapartum antibiotic treatment
• Children’s antibiotic treatment during the first 6 months of life
• Probiotic intervention during pregnancy as well as postnatally
• Having ≥1 furry pets during pregnancy or early childhood

During scheduled control visits, atopic dermatitis was clinically diagnosed by the study physicians during their scheduled control visits. They used modified criteria modified including pruritus, typical morphology and distribution and chronic, relapsing course with ≥2 eczema episodes with the minimum duration of 1 month each, or persisting chronic eczema without periods of remission.

Corticosteroid (ICS) inhalation was also used in the study as an objective representation of obstructive respiratory symptoms due to allergic sensitization. ICS purchase information was compiled from Finland’s national Prescription Register.

Skin prick testing (SPT) was also used to assess allergic sensitization, and trained study nurses performed the tests at the ages of 6 months, 12 months and 24 months. Cow’s milk and egg whites, the most relevant food allergen sources for children ≤2 years old, were observed in the SPT panels.

Study Findings

A total of 231 children either developed atopic dermatitis, were prescribed ICSs, received positive SPT results within the first 2 years of life, or had doctor-prescribed food allergies and, consequently, were identified as cases. Another 202 children were identified as healthy controls.

Lower maternal prepregnancy BMI (adjusted odds ratio [aOR], 0.15; 95% CI, 0.037 - 0.54) and maternal intrapartum antibiotic treatment (aOR, 2.21; 95% CI, 1.20 - 4.10) were associated with significantly increased risk of atopic dermatitis. Obstructive respiratory symptoms (aOR, 3.87; 95% CI, 1.07 - 14.06) were additionally associated with significantly increased risks.

Investigators also observed similar associations between the risk of allergic sensitization and lower maternal prepregnancy BMI (aOR, 0.18; 95% CI, 0.43 - 0.79) and intrapartum antibiotic treatment (aOR, 2.13; 95% CI, 1.07 - 4.22).

The investigators concluded their findings reinforce the idea that both pregnancy and early infancy represent critical periods in a child’s life for the immunologic phenotype’s development.

“We are only beginning to understand the potentially detrimental consequences of abundant antibiotic use and treacherously increasing maternal obesity to child’s long-term health,” they wrote. “Women in childbearing age should be counseled to aim for normal weight and if antibiotic treatment during childbirth or in early childhood is considered, should the potentially increased risk of allergies be taken into account.”

The study, “Early life exposures and development of allergic disease in infants with familial risks: results from ongoing probiotic intervention trials,” was published online in Acta Paediatrica.