MOTHERS-TO-BE should watch their weight gain to avoid the risk of birth complications, diabetes and hypertension.

Now, a new study is able to shed light on what the optimal weight gain for Asian women should be.

The study - by KK Women's and Children's Hospital (KKH) and Duke-NUS Graduate Medical School - involved data based on 1,592 Indian, Chinese and Malay women, who had their first antenatal visits in their first trimesters at KKH from January to April 2008.

The investigators tracked the women during their pregnancies and after childbirth.

The purpose of the study was to create a set of data tailored to women here, said Dr Tan Thiam Chye, a consultant at the KKH Department of Obstetrics and Gynaecology, and one of the principal investigators. He said that, until now, hospitals did not have local data to draw on.

"We often use Caucasian data to determine the optimal weight gain," said Dr Tan.

Optimal maternal weight gain is determined based on the pre-pregnancy weight and the Body Mass Index (BMI). BMI is calculated using the woman's weight, which is divided by the square of her height.

An Asian woman with a normal BMI, between 18.5 to 23, can put on as much as 12.7kg safely. Underweight Asian women, or those with a BMI lower than 18.5, can afford to pile on about 15.1kg during pregnancy.

Obese women with a BMI of more than 27.5 should gain no more than about 7.6kg, said the study.

About 42 per cent of the women studied were found to be overweight or obese on their first antenatal visit.

The recommended weight gain for Caucasian women could be higher than that for Asian women, said Dr Tan.

He said: "Underweight pregnant women should eat more as the baby derives nutrients from the mother. They could try taking supplements such as multi- vitamins, calcium, iron and omega three."

Those who are overweight should cut back on calorie intake and add light to moderate exercise, such as brisk walking and swimming, to their regimes.

Madam Cindy Wong, 36, who is in the seventh month of her second pregnancy, welcomes the local set of data.

She said: "Asian women tend to weigh less than Caucasian women, and figuring out an Asian woman's optimal maternal weight gain based on local data is more fitting."

The study also found that women with inadequate weight gain have an increased risk of getting gestational diabetes.

About 135 of the 1,592 women observed developed gestational diabetes.

Dr Tan said that in women with the condition, there is an increased risk of foetal heart abnormalities and getting still-born babies.

About 85 women in the study also had gestational hypertension, or high blood pressure. Dr Tan said: "Pregnant women with high blood pressure could suffer strokes or even fits.

Hypertension could possibly cause poor foetal growth." He advised pregnant women to work closely with their doctors and dieticians to manage their weight gain.

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