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

Since the 1970s, the frequency of children with asthma has risen dramatically worldwide, and up to 37% of teenagers may have symptoms. Making asthma one of the most common long term conditions in children, say the researchers.

Although reasons for this rise are unclear, environmental issues are likely to have an important role, they say, adding that over the past few decades the frequency of overweight/obesity among women at the time they get pregnant has also increased significantly.

In an effort to discover if there was any potential connection between these factors, the investigation team analyzed 7,000 15 and 16 year olds, all of whom were born in northern Finland between July 1985 and June 1986, for respiratory health.

The mothers of the participants were questioned on their lifestyle, social background, and educational attainment when they were 12 weeks pregnant. Data was also collected by their midwives on the occasion of their first antenatal visit. Which included height and weight before pregnancy and parental medical history.

Out of the teens, one in 10 wheezed and one in five had wheezed at some stage, similarly, 6% had asthma and one in 10 had at some stage asthma.

The discoveries indicated that, many early life factors were dramatically connected with subsequent respiratory symptoms. Which include, extremes of birth-weight, being raised by a single parent, a genetic predisposition and being a smoker or having a mother who smoked while pregnant.

Despite accounting for these additional factors, a mother's weight prior to becoming pregnant also had a bearing on wheeze/asthma risk and remained so.

Teenagers whose mothers were seriously overweight or obese prior to being pregnant were around 20-30% more likely to wheeze/have wheezed or have asthma currently or previously.

When the mothers' weight was examined by kilogram per height, the connection with wheeze and asthma in adolescents became highly significant, making each extra kilogram of weight an increased risk of between 2.7% and 3.5%.

Teens whose mothers were the heaviest, had an increased risk of 47% to have severe wheeze after taking into account the factors which are likely to effect the results. The researchers highlight that their discoveries do not indicate that pre-pregnancy obesity definitely causes respiratory symptoms among teenagers. However, they point to other investigations revealing connections between maternal obesity and respiratory symptoms in infants and young children, together with numerous complications during pregnancy.

They point out that normal fetal development may be interfered with by being overweight as a result of disrupted metabolic, hormonal, or ovarian activity. Weight which increases is also connected to the increasing levels hormone leptin, receptors which are found in the lung of the developing fetus.

Grace Rattue