The third trimester of pregnancy lasts from week 25 to delivery. During this time, many of the discomforts from the second trimester may remain. As the result of a growing fetus placing additional pressure on the maternal organs, existing conditions may worsen and new conditions may develop. In addition, the fetus’s size and position may make it difficult for a woman to get comfortable and sleep well, adding exhaustion to the physically demanding task of carrying a baby to term. However, most of these conditions disappear or lessen after delivery. Common changes and symptoms of the second trimester include:

• Expanding abdomen. The uterus is continuing to enlarge. By the 36^th week of pregnancy, the uterus extends to the lower edge of the rib cage. The expanding abdomen often causes the navel to bulge.
  
  
• Heartburn and indigestion. Heartburn and indigestion are common during pregnancy, even for those who have never experienced these conditions before. Although they can occur at any time during pregnancy, they typically occur during the third trimester. As the fetus grows, it causes the uterus to push on the stomach. This can result in acid reflux (backflow of stomach acid into the esophagus) and heartburn, particularly after a meal.
  
  In addition, changes in hormone levels may slow the digestion process and relax the muscles that keep the stomach acids in the proper place. As a result, stomach acids reflux, causing a burning sensation in the throat and chest. Women may benefit from avoiding spicy, fried or fatty foods and eating smaller, more frequent meals. In addition, remaining upright for a period of time following a meal may decrease the heartburn and reflux. Women should contact their obstetrician-gynecologist (ObGyn) when they experience severe or persistent heartburn that does not respond to these treatments.
  
  
• Swelling. The body produces and retains additional fluid during pregnancy. As a result, many woman experience slight swelling. It is especially common in the last few months of pregnancy. Swelling most often occurs in the legs, feet and ankles, but also may occur in the hands and face. Pressure from the uterus on the veins that return blood from the feet and legs may also cause swelling in the feet and legs. Swelling may be more severe in warmer seasons or climates.
  
  Women may benefit from drinking fluids and placing a cold compress on affected areas. Patients with swollen legs or ankles may benefit from wearing a larger shoe size and resting whenever possible with their feet elevated. Women experiencing sudden or extreme swelling of the feet, ankles, hands and face, or sudden weight gain, should immediately contact their ObGyn. It may be a sign of preeclampsia, a serious pregnancy complication.
  
  
• Continued breast growth. Most women experience breast growth throughout pregnancy. During the late stages of pregnancy, hormones cause the breasts to grow even larger in preparation for breastfeeding. By the third trimester, a woman may have an additional one to three pounds (1.4 kilograms) of breast tissue. This may result in tenderness and discomfort. Women may benefit from wearing a more supportive bra, such as a nursing or maternity bra.
  
  
• Leaking breasts. As the breasts continue to prepare for breastfeeding, an expectant mother may begin to leak colostrum (a type of milk) in the third trimester. Colostrum is an early rich precursor to the normal breast milk that the body produces. Women with leaking breasts may benefit from placing disposable or cloth nursing pads in their bras.
  
  
• Aches and pains. Expansion of the uterus and the abdomen may cause pains in the abdomen, groin or thighs. Pressure from the fetus’ head, increased weight and loosening joints can also cause backaches or aching near the pelvic bone. Backaches may also result from strain on the muscles that support the spine. Women may benefit from lying down, resting, sitting in chairs with good back support and applying heating pads or ice packs to the affected area. In addition, some gentle stretching of the muscles or massage may help ease the discomfort.
  
  Women should contact their ObGyn when pains do not improve after resting or when back pain is accompanied by fever (a sign of infection and other complications). Physicians should also be immediately notified when a patient experiences moderate or severe pelvic pain or any degree of pelvic pain that lasts more than four hours.
  
  
• Varicose veins. During pregnancy, pressure is placed on the large veins located behind the uterus. This slows the return of blood to the heart and puts pressure on the veins, causing them to swell. As a result, varicose veins may develop. These veins look swollen and cause pain. They may appear to be twisted, bulging and dark purple or blue in color. During pregnancy, varicose veins most often develop on the back of the calves, thighs and vagina. Women may benefit from avoiding long periods of standing, lying on their side and sitting with their legs and feet raised whenever possible.
  
  
• Hemorrhoids. Varicose veins that develop in the rectum. Although they may occur at any time during pregnancy, they are most common during the third trimester due to the increased pressure of the growing fetus on the veins in the rectum. Constipation may also contribute to their development. Hemorrhoids can cause itching, soreness and bleeding. Women may benefit from drinking a large amount of fluids, increasing fiber consumption and eating whole grains, fruits and leafy green vegetables. Women should also avoid straining during bowel movements.
  
  
• Shortness of breath. Pregnant women may experience shortness of breath, as the result of the uterus expanding beneath the diaphragm (the muscle below the lungs). Patients may benefit from taking long, deep breaths. Maintaining good posture is also beneficial because it gives the lungs room to expand. Light aerobic exercise (with a doctor's permission) may also reduce shortness of breath. At night, women are encouraged to use an extra pillow or sleep on their left side. Pregnant women should contact their ObGyn when they experience shortness of breath accompanied by chest pain or a cough.
  
  
• Hair changes. Pregnancy can cause changes in the texture and growth rate of hair. In many cases, pregnant women develop thicker hair during pregnancy. This is the result of hormones causing hair to grow faster and fall out less. Others notice that their hair changes color, or that it is drier or oilier than normal. In addition, some women grow hair in unwanted places, such as the face, abdomen and around the nipple. These changes usually disappear after delivery.
  
  
• Changes in nail condition. During pregnancy, hormones can cause nails to grow faster and become stronger. However, in some women the nails may become more prone to breakage and splitting. These changes usually disappear after delivery.
  
  
• Spider veins. The increased blood circulation during pregnancy can lead to the development of small reddish spots on the face, neck, upper chest or arms. These spots are commonly referred to as spider veins because they appear to sprout tiny blood vessels that resemble the legs of spiders. These marks, which are especially common among women with fair skin, usually fade or disappear after delivery.
  
  
• Increased perspiration. Pregnant women often experience increased perspiration. This is the result of growth and movement by the fetus. During hot weather, pregnant women may benefit from resting, drinking cold liquids and taking cool showers. This can prevent overheating.
  
  
• Stretch marks. Red, pink, or purple streaks in the skin caused by the stretching of the skin due to fetal growth. These scars, which usually appear over the thighs, buttocks, abdomen and breasts, most often develop in the second half of pregnancy. According to the National Women’s Health Information Center, approximately half of all pregnant women get stretch marks. Following delivery, most stretch marks fade to light lines.
  
  
• Changes in skin color. During the second half of pregnancy, hormonal changes may cause the skin to darken. Some woman may develop darker nipples or a dark line running from the navel to the pubic hairline (linea nigra). Pregnancy may also cause blotchy brown pigmentations to appear on the nose, forehead or cheeks. They may also appear over the eyes. Known as melasma or chloasma (mask of pregnancy), these changes are particularly common among women with dark hair and pale skin. Most of these skin changes fade or disappear following delivery.
  
  
• Rashes. During late pregnancy, some women may develop itchy red bumps on the abdomen. Although they are harmless, these bumps can spread to the buttocks, arms and legs, causing discomfort. The rash typically improves following delivery.
  

  

By the 26^th week of pregnancy, the fetus is about 13 inches (330 millimeters) long and weighs approximately 1¾ pounds (794 grams). Although the fetus will continue to grow and move, activity may be decreased due to the fact that there is less room in the uterus. During this trimester, the expectant mother’s body will begin preparing for childbirth and the fetus will start moving down into the birthing position. As a result, the woman may notice the fetus moving down (dropping or a process called lightening) in the abdomen. By the end of the trimester, the average fetus is about 20 inches (508 millimeters) long and weighs about 7 pounds (3 kilograms).

Major developments in the fetus during the third trimester include:

Weeks 25 to 37

• The fetus is active, moving around often
• The lungs continue to develop
• The fetus’s head moves into the required position for delivery

Weeks 37 to 42

• Delivery