Obese mothers-to-be need significantly more NHS care than pregnant women of a healthy weight and are at an increased risk of pregnancy complications, according to a study.
Maria Thornton's son Ryan was stillborn in 1995.
Doctors told her part of the reason was that they had not been able to monitor him because of her weight - which was 14 to 15 stone (89 to 95kg).
At the time, her body mass index (BMI) was 39. Doctors consider a BMI of between 19 and 24 to be healthy.
She said: "They said the placenta stopped working before he was born and he was starved of oxygen."
Maria, from Newcastle, who has had two further children and says her BMI is now 50, added: "I'd just been thinking about the practicalities, like managing after the birth and breastfeeding.
"But as far as risks to the baby are concerned, I wasn't aware there were any.
"After Ryan was born, I was told they may have been able to detect problems but, because I was carrying a lot of fluid and because there was fat there as well, they couldn't hear and feel the baby as well as they could have done in a thinner person.
"Afterwards, apart from being absolutely devastated, it heaped a whole lot of guilt on to my shoulders.
"You're supposed to be the person taking care of the baby before it is born. And to be told you're partly responsible for the death of your child is absolutely devastating."