Women whose mothers smoked in pregnancy more likely to be short and obese, new research finds

Women whose mothers smoked during pregnancy are more likely to be short and become obese later in life. Photo / 123RF

Smoking during pregnancy increases the chances of daughters being short and fat, new research led by a New Zealand scientists has found.

The study, published in Scientific Reports this week, was carried out by a group of scientists from the Auckland University-based Liggins Institute and Uppsala University in Sweden.

It found that women whose mothers smoked during early pregnancy were 51 per cent more likely to be short than women whose mothers were non-smokers and 41 per cent more likely to be affected by obesity as adults.

Other studies had shown those who were shorter than average were less likely to be successful, were treated differently and were more likely to have mental health problems.

In 2015, one in seven New Zealand mothers across all age groups and one in three teenage mothers said they smoked in early pregnancy - but the true number was likely to be higher.

The researchers analysed measurements from 22,421 women born in Sweden between 1973-1988 taken at an average age of 26 years.

Forty-two percent of the women's mothers had reported at their first antenatal visit (about 10-12 weeks into their pregnancy) that they smoked.

Lead author Dr Jose Derraik, a senior research fellow from the Liggins Institute, said it appeared the chemicals in cigarettes may turn on or off the genes involved in controlling growth.

"When a woman smokes during pregnancy, chemicals from the cigarettes travel through her bloodstream across the placenta and then to the baby, permanently changing the way the baby's body uses and stores energy," he said.

"Some of these chemicals can interfere with growth, which probably explains why babies born to mothers who smoked during pregnancy are often smaller."

The risk of obesity was higher in daughters of mothers who were heavier smokers, compared to those who smoked fewer than 10 cigarettes a day.

US research found smoking during pregnancy made babies better at forming fat cells.

"This would be useful in helping a small baby grow faster, but it would also explain, at least in part, why they have a greater risk of obesity later in life," Derraik said.

Data pulled together in 2016 from many studies identified nearly 3000 genes whose activity appeared to be affected in babies whose mothers smoked during pregnancy.

One of the studies other authors, Professor Wayne Cutfield, said stopping smoking before pregnancy also reduced the risk of pregnancy complications, birth defects, miscarriage, low birth weight and asthma in their children.