Study Title:

Associations Between Pre-pregnancy Obesity and Asthma Symptoms in Adolescents

Study Abstract

Background The high prevalence of children's asthma symptoms, worldwide, is unexplained. We examined the relation between maternal pre-pregnancy weight and body mass index (BMI), and asthma symptoms in adolescents.

Methods Data from 6945 adolescents born within the Northern Finland Birth Cohort 1986 were used. Prospective antenatal and birth outcome data, including maternal pre-pregnancy weight and BMI, and asthma symptoms in adolescent offspring at age 15–16 years, were employed. Logistic regression analyses were performed to examine the associations between relevant prenatal factors and asthma symptoms during adolescence.

Results Current wheeze (within the past year) was reported by 10.6% of adolescents, and physician-diagnosed asthma by 6.0%. High maternal pre-pregnancy BMI was a significant predictor of wheeze in the adolescents (increase per kilogram per square metre unit; 2.7%, 95% CI 0.9 to 4.4 for ever wheeze; 3.5%, 95% CI 1.3 to 5.8 for current wheeze), and adjusting for potential confounders further increased the risk (2.8%, 95% CI 0.5 to 5.1; 4.7%, 95% CI 1.9 to 7.7, respectively). High maternal pre-pregnancy weight, in the top tertile, also significantly increased the odds of current wheeze in the adolescent by 20% (95% CI 4 to 39), and adjusting for potential confounders further increased the risk (OR=1.52, 95% CI 1.19 to 1.95). Results were similar for current asthma. Furthermore, these significant associations were observed only among adolescents without parental history of atopy but not among those with parental history of atopy.

Conclusions The association demonstrated here between maternal pre-pregnancy overweight and obesity, and asthma symptoms in adolescents suggests that increase in asthma may be partly related to the rapid rise in obesity in recent years.

From press release:

Mums who are overweight or obese when they become pregnant may be programming their children to have asthma-like respiratory symptoms during adolescence, suggests research published online in the Journal of Epidemiology and Community Health.

The prevalence of children's asthma has risen substantially worldwide, since the 1970s, and up to 37% of teenagers may have asthma symptoms, making it one of the most common childhood long term conditions, say the authors.

The reasons for this increase are unclear, but environmental factors are likely to have a key role, they say, adding that the prevalence of overweight/obesity among women at the time they enter pregnancy has also increased dramatically over the past few decades.

In a bid to find out if there was any potential link between these factors, the research team assessed the respiratory health of just under 7,000 15 and 16 year olds, all of whom were born in northern Finland between July 1985 and June 1986.

Their mums had been questioned on their lifestyle, social background, and educational attainment when they were 12 weeks pregnant. Information had also been collected by midwives on the occasion of their first antenatal visit. This included height and weight before pregnancy and parental medical history.

One in 10 of the teens wheezed and one in five had wheezed at some point; similarly, 6% had asthma and one in 10 had had asthma at some point.

Several early life factors were significantly associated with subsequent respiratory symptoms, the findings showed.

These included extremes of birthweight; being brought up by a single parent; a genetic predisposition; and being a smoker or having a mum who smoked during pregnancy.

A mum's weight before she became pregnant also had a bearing on wheeze/asthma risk, and remained so, even after accounting for these other factors.

Teens whose mums had been seriously overweight or obese before they became pregnant were between 20% and 30% more likely to wheeze/have wheezed or have asthma currently or previously.

When a mother's weight was looked at by kilogram per height, the association with wheeze and asthma in adolescents became highly significant, amounting to an increased risk for every extra kilogram of weight of between 2.7% and 3.5%.

Teens whose mums were among the heaviest, were 47% more likely to have severe wheeze after taking account of factors likely to influence the results.

The authors point out that their findings do not show that pre-pregnancy obesity definitely causes respiratory symptoms among teenagers, but they point to other research showing links between maternal obesity and respiratory symptoms in infants and young children, as well as numerous complications during pregnancy.

They suggest that overweight may interfere with normal fetal development as a result of disrupted metabolic, hormonal, or ovarian activity.

Study Information

Swatee P Patel, Alina Rodriguez, Mark P Little, Paul Elliott, Juha Pekkanen, Anna-Liisa Hartikainen, Anneli Pouta, Jaana Laitinen, Terttu Harju, Dexter Canoy, Marjo-Riitta Järvelin.
Associations between pre-pregnancy obesity and asthma symptoms in adolescents
J Epidemiol Community Health
2011 August
Health Development Department, School of Health and Social Care, The University of Greenwich, London, UK .

Full Study

http://jech.bmj.com/content/early/2011/07/08/jech.2011.133777.full