Two-thirds of Australian mums-to-be are in the dark when it comes to how much weight they should gain during pregnancy.

Susie de Jersey from Queensland University of Technology's (QUT) Institute of Health and Biomedical Innovation (IHBI) and senior dietician at the Royal Brisbane and Women's Hospital said a third of women surveyed gained too much weight during pregnancy. Another third struggled to gain enough weight with some mothers recording a lower weight just before giving birth than they did before falling pregnant.

"The majority of the women in the study knew healthy eating was important, but very few could identify how much they should be eating from different food groups, particularly fruits and vegetables," she said.

"Most women said they also didn't know the recommended amount of weight they should gain during pregnancy and reported very limited advice about healthy weight gain."

While most women understand the importance of healthy eating, Ms de Jersey, who has just completed her PhD, said less than half of the study's participants viewed exercise during pregnancy as very important, possibly owing to old beliefs that physical activity was not safe for mothers-to-be, despite the opposite being widely proven.

The study, which has just been published in the Australian and New Zealand Journal of Obstetrics and Gynaecology, also showed that more than half of the women who were overweight before falling pregnant gained too much maternity weight compared to only a third of their trimmer counterparts.

"There are a lot of psychosocial factors in play - many of these women may have more negative experiences from trying to control their weight in the past," she said.

"The reality is that some women find it easier to control their weight than others both before and during pregnancy.

"We know that we need to acknowledge their prior experiences and work with them to improve their confidence and to help them engage in healthy behaviours."

Ms de Jersey said the key to helping women achieve healthier weight gain during pregnancy was by taking an individualised approach, and to give intensive support to mothers who battled with weight control on either end of the scale prior to falling pregnant.

"Pregnancy is an important time that influences being overweight in both mothers and their babies," she said.

"Gaining too much or not enough weight, eating a poor diet and being physically inactive can affect the health of both mothers and their babies well into the future.

"Antenatal care in the past has been about delivering a live baby, with chronic disease prevention and the long-term health of mothers and their babies rarely considered.

"For most healthy, younger women, pregnancy is one of the few times they will visit health professionals regularly. It's the perfect opportunity to change the whole environment for their families.

"Giving intensive support to mothers at this time may help to instil healthy habits that can have flow-on effects for not only the mother and baby during pregnancy, but also to help lower the child obesity rate."
  • If your pre-pregnancy BMI was: Less than 18.5 kg/m² you should gain: 12½ to 18 kg
  • If your pre-pregnancy BMI was: 18.5 to 24.9 kg/m² you should gain: 11½ to 16 kg
  • If your pre-pregnancy BMI was: 25 to 29.9 kg/m² you should gain: 7 to 11½ kg
  • If your pre-pregnancy BMI was: Above 30 kg/m² you should gain: 5 to 9 kg