Trimester Three – Weeks 21 through 27

In the second half of the second trimester, the pregnancy is in "full swing"; the "bump" is fully visible, and a fetus born at the end of this trimester has strong chance of survival.  Changes to a woman's body, and development of the fetus, are considerable during this time.

Second Trimester Fetus Growth and Development

Week 21

During this week, the bone marrow takes over red blood cell production from the liver and spleen.  The fetus begins swallowing small amounts of sugar in the amniotic fluid.

Week 22

The fetus is now able to sense taste and touch.  For male fetuses, the testes descend into the abdomen.

Week 23

The fetus begins to practice breathing by drawing amniotic fluid into and out of the lungs.  The skin continues to mature and fat deposits increase.

Week 24

The fetus's fully-developed inner ear gives the fetus a sense of balance, and it may adopt a regular sleeping position.

Week 25

The fetus's sensory system becomes more refined.

Week 26

The eyes are fully developed, although the lids remain closed.

Week 27

The lungs, liver, and immune system continue to develop, and the fetus weighs about two pounds.  With intensive medical attention, a fetus born at 27 weeks has about an 85 percent chance of survival.

Second Trimester Pregnancy Symptoms

As the second trimester progresses, a woman's breasts enlarge, and she can expect to gain about four pounds per month for the rest of the pregnancy.  Changes in circulation can cause breathing and gum problems, dizziness, and cramps.  The growing uterus cramps the abdominal area, causing indigestion, heartburn, shortness of breath, and sleeping problems.  Hormonal fluctuations can cause constipation and bladder and kidney infections, although mood swings and lethargy decrease.

Continued Reading:

Trimester Three - The First Half