Whitcome's study included 19 pregnant women between the ages of 20 and 40. The researchers found that when the women were standing, they naturally increased their spine's lordosis, sometimes by as much as 60 percent. Even when the women extended their hips only slightly, their lower backs were extended by as much as 28 degrees.
However, despite what appear to be nature's best intentions, back pain is still a common complication during pregnancy.
"Women, by and large, make pregnancy look so easy, but there are very few women who have experienced pregnancy who haven't had some back pain," said Whitcome. But, she added, "without these adaptations, I think this back pain would be exceedingly worse. I think these adaptations mediate some of the intensity of back pain."
Dr. Miriam Greene, an obstetrician at New York University Medical Center, agreed that "there's plenty of back pain in pregnancy," but said she wasn't convinced that the differences in male and female spines account for the majority of a woman's pregnancy stability.
"I think the reason why pregnant women don't tip over is that the placenta produces relaxin, a hormone released in pregnancy that spreads your pelvis, making it wider, and giving you a wider stance. That's why you walk like a duck when you're pregnant," she said.
Greene said a pregnant woman's center of gravity starts to shift slowly as she gains weight, with the majority of the shift occurring in the third trimester.
To prevent falls and back strain, Greene recommends wearing flat shoes, ditching heavy bags, taking extra care anytime you lift objects, and perhaps wearing a pregnancy belt. Additionally, she said that pregnancy exercise classes can help maintain the strength in your back.
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