Women often experience back pain when they are pregnant. suppose a woman's mass before pregnancy is 66 kg and her center of mass when standing is located directly above the hips. by the thirty-fourth week of pregnancy, she has gained 8.2 kg (the combined mass of the fetus, the placenta, and the amniotic fluid). the center of mass of this 8.2 kg is 16 cm in front of the hips. if she hasn't changed her posture, how far in front of the hips is her center of mass? women have three wedge-shaped lumbar vertebrae, whereas men have only two. this evolutionary adaptation permits a greater curvature of the lumbar spine to keep a pregnant woman's cm above the hips.