Mothers who gain or lose lots of weight between pregnancies could be putting their baby at risk, experts have warned.
The trend for new mothers to lose lots of weight in a short amount of time could be detrimental to their infant's health, they warned.
But women who pile on the pounds after giving birth also put their next child at risk, they said.
Effects can include premature birth, greater risk of stillbirth and high blood pressure.
Women should therefore try to maintain a healthy weight before, during and after pregnancy to give their child the best start in life, said two doctors writing in the British Medical Journal (BMJ).
The experts are Jennifer Walsh, a specialist registrar in obstetrics and gynaecology at Coombe Women's Hospital in Dublin, and Deirdre Murphy, professor of obstetrics at Trinity College, University of Dublin, and Coombe Women's Hospital.
They warned that the current obsession with what women weigh, and its series of conflicting messages, also extended into pregnancy.
"Women of reproductive age are bombarded with messages about diet, weight, and body image," they said.
"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.
"With at least half of all pregnancies unplanned, women need to be aware of the implications of their weight for pregnancy, birth, and the health of their babies."
