Overweight mothers-to-be are risking the health of their unborn children and putting an extra strain on the NHS, according to researchers on Teesside.
It is now 'unfashionable' to monitor pregnant women's weight
The study, by the University of Teesside, found a lack of readily available weight management guidance and support for obese mothers.
It called for pregnant women to have their height and weight monitored as a matter of routine.
However, it also stressed that crash dieting be avoided during pregnancy.
Maternity units around the north east had expressed concern about a growing number of clinically obese pregnant women.
The research found a number of implications for maternity services, including the need for stronger medical equipment such as delivery beds to support heavy mothers.
They should also be referred to a consultant rather than a midwife, and discouraged from having a home birth or using birthing pools.
Professor John Wilkinson, director of the North East Public Health Observatory, said: "Until the late 1980s the height and weight of pregnant women was regularly monitored.
"But this became unfashionable in recent years as it was felt this caused unnecessary concern and worry to women who had gained a couple of extra pounds.
"Our study recommends that a routine system of monitoring the height and body weight of pregnant mothers is extended to all maternity units."