Stages of Pregnancy
2nd Trimester Baby
The 2nd Trimester Baby: 15‑27 Weeks
During the 2nd trimester (the next 3 months of your developing baby’s life) the brain develops a lot. Most of the brain’s development begins now and continues after your baby’s birth. During the 2nd trimester until about 24 weeks, the fetus cannot live outside your body because its lungs, heart, and blood systems have not developed enough.
(Please note that although the term “baby” is used throughout this website, during the first 7 weeks the actual term for your developing baby is an “embryo,” and from week 8 until birth it is a “fetus.”)
Time |
Weight and Length |
Events |
16 weeks |
16 cm (6 1/2 in.) |
The face looks more human, the head has hair, the ears stand out, and the developing baby can hear your voice. Between 16 to 20 weeks, you may feel its movements. You may not feel the movements until 18 to 20 weeks, especially if this is your first pregnancy.  16 weeks, 16 cm (6 1/2 in.)
|
17 weeks |
The developing baby begins to store some of your antibodies. This slowly increases until birth. |
|
20 weeks |
25 cm (10 in.) |
Eyebrows and eyelashes appear. A fine downy hair (lanugo) appears all over the baby’s body and may be present at birth. The skin is thin, shiny, and covered with a creamy protective coating called vernix. Oil glands appear. The baby’s legs lengthen, and move well. Teeth develop – enamel and dentine are being formed. (This can begin as early as 14 weeks.) By the end of the fifth month, the developing baby is about half the length of a newborn. During the second trimester, meconium (the baby’s first stool) begins to appear in the intestines.  20 weeks, 25 cm (10 in.
|
24 weeks |
Sweat glands form. The baby has a lean body with red and wrinkled skin. Early breathing movements begin. A substance called surfactant is formed in the lungs. This substance helps the lungs to expand normally after the baby is born. |
|
26 weeks |
30 cm (12 in.) |
The baby’s outline may be felt through your abdomen. The eyes may be open now. |
