During the second trimester, every organ in your body is busy adapting to the changes of pregnancy. Your growing uterus is the most obvious sign of change, as it begins to protrude out of the abdominal cavity, giving you a much more rounded shape. As the uterus enlarges, it pushes other internal organs out of the way and causes tension in surrounding muscles and ligaments. You may feel pain in your lower abdomen because the structures that support the uterus are stretching and thickening. This type of pain is not severe and it does not pose a threat to your pregnancy. If you are bothered by abdominal pain, try lying down and resting for a short time. Relaxation exercises will help and a warm bath may soothe the aches away.
To allow your baby to pass through your pelvis during birth, the joints in your pelvic area begin to soften and loosen. Sometimes, the panels of muscle running along the front of your abdomen will separate under pressure from your expanding uterus. As well, the growing weight of your fetus changes your center of gravity, causing you to compensate by adjusting your posture. All of these factors may result in back pain during your last two trimesters.
To minimize the discomfort, you should try to maintain a correct posture, with your pelvis tucked in and your shoulders back. Sit with your feet slightly elevated, try not to stand for long periods and sleep on your side with a pillow between your knees and one under your abdomen. Exercises to strengthen your abdominal muscles will also reduce the tension in your back.
The hormones that loosen your pelvic joints also affect your intestinal tract, slowing down digestion and causing food to remain longer in your stomach. This allows more time for nutrients to be absorbed into your bloodstream for use by the fetus. Unfortunately, it can also result in nausea, indigestion and bloating. Heartburn is another symptom of this slowdown in digestion. Heartburn develops when the contents of your stomach flow backward into your esophagus. The stomach acids irritate the esophagus, creating the burning sensation that gives heartburn its name. Eating small meals more often during the day can help minimize heartburn. You should also avoid drinking fluids with your meals; instead, have them between meals. Because your intestinal muscles are more relaxed, you may also become constipated, a condition that is aggravated by the pressure of the growing uterus on your rectum.
As you progress through your second trimester, your heart is working twice as fast as it was before you were pregnant, your blood volumes are 50 percent higher and your kidney functions are still accelerated. Skin darkening is a very common symptom at this stage, especially among dark-skinned women. The skin around your nipples, navel and vulva will become a deeper color and you may notice the appearance of a dark line between your navel and your pubic bone. This darkening of the skin usually disappears after pregnancy.
Weight gain tends to vary during the second trimester. On average, you should expect to gain about 0.5 kilograms (1 pound) a week after the first three months. You should be striving for a steady, gradual weight gain, without sudden increases or decreases.
This is a very exciting time, because you will soon begin to feel your baby move. The kicking and fluttering movements of your growing baby will make the pregnancy feel more emotionally involving and real to you. You can expect to detect some fetal activity by the 20th week of pregnancy.
As you enter your fourth month, most of your baby’s bones are formed, facial features are becoming more defined and external genitalia are evident. The brain is growing and the baby’s head proportions are more balanced. By the end of the second trimester, your baby’s eyes are opening and closing, there is some fat accumulating under the skin and regular intervals of sleeping and waking are beginning. At this stage the baby has grown to 23 centimeters (9 inches) and weighs nearly 670 grams (just over one pound). After 24 to 26 weeks, there is a strong possibility that the baby could survive outside the womb.