We can now add better bones to the benefits of prenatal exercise, according to a study in China. Women normally lose bone density during pregnancy and regain it after childbirth. To compensate for this natural process of bone turnover, moms-to-be produce more of the hormone estrogen, which helps protect bone mass, and their bodies more easily absorb the bone-building mineral calcium from food and supplements.
The researchers wondered if bone turnover could also be affected by physical activity. They compared expectant women who exercised at least 10 hours a week with those who didn’t exercise at all and found that the exercisers, as expected, lost some bone mass as they approached their due date—but at far lower rates than the sedentary women.
Maintaining healthy bone mass during pregnancy is important. If mom’s dietary calcium is insufficient, the fetus will draw whatever calcium it needs from the mother’s bones. Getting enough of this mineral is especially critical during the last trimester, when the fetus is growing fast and needs calcium to develop its own skeleton.