"To lower the risk of obstetrical complications, they may have to start changing their lifestyle before or immediately after they conceive," said lead author Dr. Alan Peaceman, chief of maternal fetal medicine at Northwestern University Feinberg School of Medicine.
Seven teams of investigators recruited 1,150 participants, with 579 women having the lifestyle intervention and 571 having standard care, for the LIFE-Mom trials, which ran from the second trimester to birth.
Each trial offered a varied lifestyle intervention, but all aimed to improve diet quality and reduce calories, increase physical activity and incorporate behavior strategies such as self-monitoring.
About 62 percent of the women in the intervention groups, versus 75 percent in the control groups, exceeded the National Academy of Medicine recommendations for pregnancy weight gain. The recommendation is overweight women limit their pregnancy weight gain to 15 to 25 pounds and obese women to 11 to 20 pounds, compared to 25 to 35 pounds for non-overweight women.
"It's a very hard nut to crack," Peaceman said.
In the early 2000s, physicians started noticing that excessive pregnancy weight gain was associated with certain pregnancy complications: higher incidence of high blood pressure, gestational diabetes and cesarean sections.
"Then we started seeing more worrisome things," Peaceman said. "Excess maternal weight gain was not just associated with bigger babies, but those babies ended up with an increased risk of obesity and childhood diabetes."
The researchers are hopeful that there will be longer-term benefits of the interventions in the infants, such as less childhood obesity or fewer metabolic abnormalities such as childhood diabetes.
The study was published Thursday in the journal Obesity.