Your weight during pregnancy determines the size of your baby

Being overweight during pregnancy could determine the SIZE of your baby

The study has also revealed mums-to-be with high blood pressure tend to have smaller babies

Being overweight or obese in pregnancy causes babies to be born larger, according to new research.

The study, led by the Universities of Bristol and Exeter, also found that mothers with a higher blood sugar - even within a healthy range - tend to have bigger babies .

However, having higher blood pressure in pregnancy causes babies to be born smaller, the international research collaboration found.

Researchers found that mothers' blood lipids, which are also related to being overweight, did not seem important in determining the baby's size.

Dr Rachel Freathy, of the University of Exeter Medical School, said: "Being born very large or very small can carry health risks for a newborn baby, particularly when that's at the extreme end of the spectrum.

"Higher and lower birth weights are also associated with diseases such as Type 2 diabetes later on in life.

"Understanding which characteristics of a mother influence the birth weight of her offspring may eventually help us to tailor management of a healthy pregnancy, and reduce the number of babies born too large or too small."

The work, published in medical journal JAMA, used data from more than 30,000 healthy women and their babies across 18 studies.

Researchers examined genetic variants associated with mothers' body mass index, blood glucose and lipid levels and blood pressure, along with measurements of these characteristics in pregnancy.

They also studied the weight of all the babies at birth.