Women who have had weight loss surgery should wait at least a year before trying for a baby, experts have warned.

Having a baby after surgery is safer and associated with fewer complications than becoming pregnant when morbidly obese, say doctors.

But patients should still be treated as high-risk and be "strongly advised" not to get pregnant for 12 to 18 months afterwards, a review suggests.

Obesity among women of childbearing age is expected to rise to 28% by 2015.

National guidelines recommend weight loss surgery - most commonly done through a gastric band or gastric bypass - as an option for anyone with a body mass index of more than 40kg/sq m.

The review of the latest evidence, published in The Obstetrician and Gynaecologist journal, says that it will become more and more common for doctors to be asked for advice about the safety of becoming pregnant after bariatric surgery.

Yet there is a lack of guidance on how to manage such patients.
Surgical complications

Researchers found that most women who get pregnant after bariatric surgery would have no complications, with one study suggesting 79% would have a straightforward pregnancy.

But there can be surgical complications with the potential for a gastric band to slip or move during pregnancy, leading to severe vomiting.

One study found that band leakage was reported in 24% of pregnancies.

Women who become pregnant after weight loss surgery should be managed by a team of experts that includes an obstetrician, surgeon, fertility specialist and nutritionist, the review recommends.

The researchers also pointed out that the female patients should receive advice and information before they got pregnant, on contraception, nutrition and weight gain, and vitamin supplements.

Advising women who have had weight loss surgery to wait at least 12 months before trying to conceive, they pointed to research showing an increased risk of miscarriage.

One study found that 31% of pregnancies occurring within 18 months of having weight loss surgery ended in spontaneous miscarriage compared with 18% in women who got pregnant after 18 months.

Rahat Khan, consultant obstetrician and gynaecologist at Princess Alexandra Hospital NHS Trust in Harlow, Essex, and co-author of the review, said this issue was affecting an increasing number of women of childbearing age.

"In light of current evidence available, pregnancy after bariatric surgery is safer, with fewer complications, than pregnancy in morbidly obese women," he said.

But he added this group of women should still be considered to be high risk.

Daghni Rajasingam, of the Royal College of Obstetricians and Gynaecologists, said obesity was associated with a number of serious risks in pregnancy, and women should be supported to lose weight before conception.

"It is important that women are aware of the increased risk of maternal and fetal complications associated with obesity, and they should be advised about the possible strategies to minimise them prior to conception."