Another milestone comes halfway through this month. It's known as quickening, and it's the first time you feel your baby move. The fetus has been moving for a few weeks, but now that its bones are harder and its muscles and limbs are stronger, the movements become noticeable.
Almost all the follicles from which your baby's hair will grow are in place. Some babies are born with long, thick hair, others with almost none, but it will all fall out during the first months of life. Fingernails grow longer this month, and toenails are just starting to grow.
The number of nerve cells in your baby's brain increases rapidly this month, especially in the front of the brain, where thinking takes place. The baby's senses, too, are beginning to awaken, and it may be able to hear sounds, such as the flow of blood, the beating of your heart, and the rumblings of your stomach.
Inside your baby's intestines, the first stool, called meconium, is forming. If your baby is a girl, eggs are starting to develop in her ovaries. At about 20 weeks, you may be able to hear your baby's heartbeat with a stethoscope.
Near the end of this month, several changes take place in your baby's skin. It becomes covered with a fatty yellowish substance called vernix, which protects its skin from the constant exposure to amniotic fluid. Under the skin, particularly around the neck and back, a special tissue called brown fat is forming. Until it disappears a few weeks after birth, brown fat produces heat, which the baby needs after leaving the warmth of your womb.
At the end of this month, your baby is about 7 inches long and weighs 10 to 12 ounces.