Obesity weighs heavily on expectant moms, babies
OTTAWA — A new generation of expectant mothers with extreme obesity is giving birth to higher rates of serious pregnancy and delivery complications for women and babies, Canadian doctors warn.
New research involving nearly 7,000 women who gave birth at The Ottawa Hospital finds that the heavier the woman, the greater the risk for pregnancy-induced hypertension, gestational diabetes and emergency caesarean sections.
Obese expectant mothers also face a heightened risk of pre-eclampsia, a rapid and potentially life-threatening rise in blood pressure and protein in the urine that, if undiagnosed, can lead to kidney or liver failure, brain swelling, seizures and death. The risks to babies include fetal growth restriction and premature birth.
Twenty-three per cent of women of child-bearing age in Canada are obese, according to Statistics Canada. Obstetricians say that it is not unusual today to see expectant mothers with a body mass index, or BMI, of 50. Obesity is defined as a BMI of 30 or more.
The phenomenon has forced maternity wards to purchase stronger operating room tables, extra-wide chairs, heavier scales and other specialized equipment to cope with the growing proportion of dangerously obese pregnant women in labour.
“This wasn’t an issue five years ago,” said Dr. Mark Walker, co-author of the new study and a high-risk obstetrician at The Ottawa Hospital. High-risk baby doctors are seeing more women who are not only obese, “but morbidly obese, with BMI’s over 40,” said Walker, a professor of obstetrics and gynecology at the University of Ottawa.
Obese women are more likely to give birth to abnormally large babies, increasing the risk of injury at delivery. The greatest risk is shoulder dystocia, an obstetric emergency where the baby’s shoulders get stuck in the birth canal. The longer it takes to dislodge the baby, the higher the risk of lasting complications such as nerve damage that can lead to permanent paralysis in an arm, decreased oxygen supply causing cerebral palsy and, in rare cases, death.
But the problems start at the beginning of pregnancy: Babies born to obese mothers are at a twofold higher risk of congenital heart disease, spina bifida and other birth defects. “Pretty much any birth defect is more common in obese women,” Walker said. Yet the excess fat tissue can make it extraordinarily difficult to detect anomalies by ultrasound.
Most ultrasound probes are designed to work at a depth of about five centimetres, said study co-author Dr. Laura Gaudet, a high-risk obstetrician at The Moncton Hospital in Moncton, N.B.
“It’s not uncommon to be working at a depth of 20 to 30 centimetres,” she said.
Gaudet said she is struck by the degree of obesity she’s seeing in her patients. “More and more, I’m seeing younger and younger women falling into the class III obesity range,” she said — women with a BMI of 40 or more.
“The ones that concern me the most are younger women — teens and women in their early 20s. But I also see class III obesity not uncommonly in my older mums, women over the age of 35.”
Appearing in this month’s issue of the Journal of Obstetrics and Gynaecology Canada, the new study involved 5,574 women who delivered a baby at The Ottawa Hospital between Dec. 1, 2007 and March 1, 2010.
Compared with women with a normal BMI, overweight and obese women had a significantly higher likelihood of having pre-eclampsia or gestational diabetes. Rates of emergency and elective C-sections increased in parallel with increasing BMI as well. Nearly one in two women with class III obesity delivered via C-section.
Obese women were also nearly twice as likely to be induced, “and, when we induce labour, we inevitably see an increased risk in caesarean section,” said Gaudet, adding that a surgical birth “is not an easy proposition in these patients.”
“If we can get to young women and prevent them from ever becoming obese in the first place, then when they enter pregnancy their outcomes are going to be better,” Gaudet added. Babies born to obese mothers are more likely to be obese and to develop diabetes and high blood pressure later in life. “This is a chance to interrupt the inter-generational cycle of obesity,” she said.