Obese women who give birth for the first time are more at risk of having premature and small-weight babies, according to research.
The experts' findings, published in the American Journal of Obstetrics and Gynaecology, also found that obese women had more of a chance of suffering with pre-eclampsia.
A total of 385 obese women, who were pregnant for the first time and had a BMI over 30, took part in the study.
Babies with a lower-than-normal birthweight accounted for 18.8% of births compared with around 10% in the average population.
A total of 13.4% of the babies had a higher than normal birthweight, compared with 10% in the average population. Meanwhile, 11.7% of the women got pre-eclampsia compared with 6% of obese women with one or more previous pregnancies and only 2% of the average population.
The premature birth rate was 11.9% - compared with the national average of 7% - and higher than previously reported in obese women who had been pregnant before.
The study, which was funded by the baby charity Tommy's, also found that the Caesarean section rate of 39% in obese women was the highest ever reported in the world.
"Is this report only stating the blinking obvious?! Fat people are in danger of increased complications in almost every area of health, what next - fridges contain cold objects?!" - Joe Delaney, Eastbourne
"All this study does is observe this, it seems to draw no conclusions as to why this might be the case ... is this yet another case of fat phobia?" - Chantelle Charnley, Lancashire