A study is warning that mothers who put on a lot of weight or seriously trim down between pregnancies may be putting their next baby at risk.
The experts from Coombe Women's Hospital in Dublin, and Trinity College, University of Dublin, say women should try to maintain a healthy weight before, during and after pregnancy to give their child the best start in life.
Their research, published in the British Medical Journal (BMJ), looked at two studies.
The first, from Sweden, found that gaining three Body Mass Index (BMI) units between births "significantly increased the rate of term stillbirth, independent of obesity related diseases".
A second study, published in the American Journal of Obstetrics and Gynaecology, found that women whose BMI fell by five or more units between pregnancies increased their risk of premature birth.
The authors of the latest research said: "Women of reproductive age are bombarded with messages about diet, weight, and body image.
"There is growing concern on the one hand about an epidemic of obesity, and on the other about a culture that promotes 'size zero' as desirable, irrespective of a woman's natural build.
"Pregnancy is one of the most nutritionally demanding periods of a woman's life, with an adequate supply of nutrients essential to support foetal wellbeing and growth.
"However, the potential to provide women with conflicting information about weight, weight gain, and weight loss extends to pregnancy and birth outcomes."