Week 20: The halfway point

Halfway into your pregnancy, or 18 weeks after conception, you might be able to feel your baby's first movements, also known as quickening. If you've been pregnant before, you might have begun feeling your baby's movements a few weeks ago.

By now your baby might be about 6 1/3 inches (160 millimeters) long from crown to rump.

Week 21: Baby can swallow

Twenty-one weeks into your pregnancy, or 19 weeks after conception, your baby is poised to gain more weight. By this week your baby is becoming more active and is able to swallow.

Week 22: Baby's hair becomes visible

Twenty-two weeks into your pregnancy, or 20 weeks after conception, your baby is completely covered with a fine, down-like hair called lanugo. The lanugo helps hold the vernix caseosa on the skin. Your baby's eyebrows might be visible.

By now your baby might be 7 1/2 inches (190 millimeters) long from crown to rump and weigh 1 pound (460 grams).

Week 23: Fingerprints and footprints form

Twenty-three weeks into your pregnancy, or 21 weeks after conception, your baby's skin is wrinkled, more translucent than before and pink to red in color.

This week your baby begins to have rapid eye movements. Your baby's tongue will soon develop taste buds. Fingerprints and footprints are forming. For boys, the testes are descending from the abdomen. For girls, the uterus and ovaries are in place — complete with a lifetime supply of eggs.

With intensive medical care, some babies born this week might be able to survive.

Week 24: Real hair grows

Twenty-four weeks into your pregnancy, or 22 weeks after conception, your baby is regularly sleeping and waking. Real hair is growing on his or her head.

By now your baby might be about 8 inches (210 millimeters) long from crown to rump and weigh more than 1 1/3 pounds (630 grams).

Week 25: Baby responds to your voice

Twenty-five weeks into your pregnancy, or 23 weeks after conception, your baby's hands and startle reflex are developing. Your baby might be able to respond to familiar sounds, such as your voice, with movement.

Week 26: Baby's fingernails develop

Twenty-six weeks into your pregnancy, or 24 weeks after conception, your baby has fingernails.

Your baby's lungs are beginning to produce surfactant, the substance that allows the air sacs in the lungs to inflate — and keeps them from collapsing and sticking together when they deflate.

By now your baby might be 9 inches (230 millimeters) long from crown to rump and weigh nearly 2 pounds (820 grams).

Week 27: Second trimester ends

This week marks the end of the second trimester. At 27 weeks, or 25 weeks after conception, your baby's lungs and nervous system are continuing to mature — and he or she has likely been growing like a weed. Your baby's crown-to-rump length might have tripled since the 12-week mark.

Dec. 04, 2012 See more In-depth