Side effects: Breathlessness, heartburn, darker nipples, lumpy tissue in armpits or on chest, skin tags
Pregnant women actually breathe easier; they just don't always realize it. Progesterone reprograms the brain so that you'll inhale 30 to 40 percent deeper to supply all that extra blood with oxygen. Some women even add inches to their rib cage as a result of increased lung size. "Your bones change in proportion to the tissue you have to support. After delivery, they'll probably return to normal," says Dr. Sears.
On one hand, this improved breathing capacity, combined with more cortisone, means about a third of asthmatics can—with their doctor's permission—go off their medication. (In another third, the asthma gets worse; it stays the same for everyone else.) On the other hand, many pregnant women continue to feel breathless even though they're getting plenty of air, partly because the baby is transferring more carbon dioxide to you. In the last trimester, breathlessness occurs because the growing uterus limits lung space.
Heartburn (or gastroesophageal reflux) is caused by the relaxation of intestinal muscles in the first trimester. Digestion slows, letting food sit longer and creating more acid in your stomach. At the same time, this effect loosens control of the esophagus, which separates the stomach and throat. The contents of the stomach are then able to move backward into the esophagus, or even higher in the throat.
The other chest-related changes—larger, more sensitive breasts, and darker nipples (from extra pigment)—are more predictable, but may come with surprises of their own. Many women have breast tissue all across their chest and in their armpits, and hormones can cause it to swell into lumps.
Hormones also stimulate mid-pregnancy growths on the chest (and elsewhere), such as tiny, harmless polyps of skin, known as skin tags, and hair where there wasn't any. When hormone levels drop after birth, these usually disappear.
Side effect: Backache
Back pain can become a problem for pregnant women long before an enlarged belly causes the changes in posture that pull and strain muscles. Why? As early as eight weeks after conception, connective tissue in the pelvis softens, and the sacroiliac joint in the lower back loosens. In the third trimester, sciatic pain can develop if the baby parks himself on the nerve.
Side effects: Frequent urination, bladder infections, itchiness
You knew you would go to the bathroom a lot, but you may not have known that you would go so little, so frequently. That's because the bladder never completely empties during pregnancy; it's 30 to 50 percent full at any given moment as a result of progesterone's relaxing effect on the muscles. At the same time, the kidneys work about 40 percent harder to remove waste from both you and the baby. Aside from the uncomfortable sensation of never emptying your bladder, this phenomenon also increases the risk of urinary infection—and may make it harder to detect when you have one. If going to the bathroom becomes painful at any time, contact your obstetrician.
You may experience itchiness during the third trimester, especially on your abdomen. It's typically the annoying but harmless result of hormones and stretching skin. If it becomes intense or prolonged, though, tell your doctor; it could indicate a liver problem known as choletasis.
Legs and Feet
Side effects: Cramps, varicose veins, swelling
Cramps in your feet and calves are normal in the second and third trimesters, and may be caused by either fatigue or the uterus putting pressure on the nerves in your legs.
Varicose veins and swollen feet are two other ailments that usually occur once your baby has made her physical presence known. At that point, the weight and position of the uterus impairs blood flow, enlarging already swollen veins in the legs, rectum (hemorrhoids), and vulva. As they become more visible, they'll sometimes create discomfort. Your feet are likely to swell as part of the fluid-retention process, and because of your increasing weight.
An End in Sight
As you observe the changes taking place in your body, take comfort in knowing that what pregnancy gives, childbirth most often takes away. Around three hours after delivery, some hormone levels return to normal, says Dr. Moore, often quickly eliminating many bothersome side effects that have lasted for months.
In the days following my daughter's birth, I remember gleefully stretching my feet and pointing my toes (no cramps), walking up the stairs (without losing my breath), and ceremoniously dropping my bottles of antacid in the trash one by one. Ultimately, I was left with the one effect of pregnancy that really lasted: Her name is Anna.