The hormonal and physiological changes that come with pregnancy are unique. Pregnant women experience sudden and dramatic increases in estrogen and progesterone. They also experience changes in the amount and function of a number of other hormones. These changes don’t just affect mood. They can also: create the “glow” of pregnancy, significantly aid in the development of the fetus and alter the physical impact of exercise and physical activity on the body.
Estrogen and progesterone are the chief pregnancy hormones. A woman will produce more estrogen during one pregnancy than throughout her entire life when not pregnant. The increase in estrogen during pregnancy enables the uterus and placenta to: improve vascularization (the formation of blood vessels), transfer nutrients and support the developing baby. Estrogen levels increase steadily during pregnancy and reach their peak in the third trimester. The rapid increase in estrogen levels during the first trimester may cause some of the nausea associated with pregnancy. During the second trimester, it plays a major role in the milk duct development that enlarges the breasts.
While these hormones are absolutely critical for a successful pregnancy, they also can make exercise more difficult. Because the ligaments are looser, pregnant women may be at greater risk for sprains and strains of the ankle or knee. However, no studies have documented an increased rate in injury during pregnancy. A pregnant woman’s entire posture changes. Her breasts are larger. Her abdomen transforms from flat or concave to very convex, increasing the curvature of her back. The combined effect shifts the center of gravity forward and may lead to changes in her sense of balance.
