This week, your baby has fully developed sex organs, although they will be difficult to see on your pregnancy ultrasound. In boys, the prostate gland is developing. In girls, the ovaries have formed and have moved down into the pelvis.
Your baby is 3 ½ inches long, crown to rump (head to butt) and weighs about 1 ½ ounces. Her skin is very translucent, although she is beginning to develop a downy, very fine hair called lanugo over her body for insulation. She will have this hair until she develops enough fat deposits to regulate her temperature, usually shortly before she’s born.
This week, your baby is strengthening her muscles by moving and kicking a little more. She is becoming more flexible and stronger every day. She is even practicing moving her facial muscles, as she frowns, grimaces, and squints.Your baby is in the midst of an impressive growth spurt. Within the next month or two, she will triple in length and grow to reach the one-pound mark. (source: smartmomma.com)