Birth risk: The number that affects every pregnant woman
A GOLDILOCKS dilemma hangs over pregnant women, as an extensive study shows that having a BMI which is "just right" can prevent birth complications and even death.
It found being too thin was almost as risky as being too fat.
Research that tracked 750,000 women showed it had never been more vital to keep weight controlled if planning a pregnancy.
For almost a decade US scientists examined the association between pre-pregnancy BMI and severe maternal morbidity.
A "just right" BMI is 18.5 to 24.9, less than 18.5 is considered underweight and overweight is 25 to 29.9.
Maternal complications include amniotic fluid embolism, hysterectomy, uterine rupture, antepartum haemorrhage and thromboembolism.
Underweight women were 1.2 times more likely to have significant complications, while overweight women showed a steady weight-related increase in risk up to 1.4 times that of their normal-weight counterparts.
Queensland obstetrician Gino Pecoraro told The Courier-Mail that the findings were relevant to Australian women.
"What women eat in pregnancy has been known to be important for some time, perhaps it is now important for women to watch how much they eat," Dr Pecoraro said.
"While the study is not able to say that the increased weight caused the complications, it does suggest a statistically significant association, which makes trying to keep weight in check very worth while."
Kate Wright, of the Gold Coast, is 25 weeks pregnant with twins. Before her pregnancy she was a body builder.
"Because of my background I carry a lot of muscle mass, and that can really throw off the BMI reading so I don't live my life based on BMI, but I do believe in eating healthy and keeping healthy," she said.
"I went through IVF to have my babies and I want to do everything I can to try to make the pregnancy go smoothly."