According to a new research study, continuing to work in late stages of pregnancy by some women pose a higher risk to their children.

The researchers at the University of Essex said that working in late stages of pregnancy is as bad as smoking. They warned that women who work up till their due dates are more likely to have underweight babies. They studied data from data from two earlier studies in the UK and one in the US.

They study found that women who continued to work during the ninth month of their pregnancy had babies who were on average around half a pound lighter compared to those who stopped work between six and eight months. The benefits of stopping work were higher for uneducated women, indicating that effect of working during pregnancy was higher for physically demanding work.

The researchers identified 1,339 children whose mothers took part in the British Household Panel Survey that was conducted between 1991 and 2005 in the UK. They also examined the Millennium Cohort Study as well as National Survey of Family Growth, relating to births in the US between the early 1970s and 1995.