The second trimester: Your baby's growth and development in middle pregnancy
The fourth month of pregnancy signals another milestone: the start of the second trimester. Here's what's happening during the second trimester of pregnancy.
Month four of pregnancy
Your baby's fingers and toes are well defined; eyelids, eyebrows, eyelashes, nails and hair are formed. Teeth and bones become denser in the second trimester of pregnancy. Your baby can even suck his or her thumb, yawn, stretch and make faces.
The nervous system is starting to function at this point in pregnancy. The reproductive organs and genitalia are now fully developed, and your doctor or midwife can see on ultrasound if you are having a boy or a girl. Your baby's heartbeat may now be audible through an instrument called a Doppler.
By the end of the fourth month, your baby is about 12-15cm long and weighs about 140g.
Month five of pregnancy
Hair is beginning to grow on your baby's head and lanugo, a soft fine hair, covers his or her shoulders, back, and temples. This hair protects your baby and is usually shed at the end of the baby's first week of life.
Your baby's skin is covered with a whitish coating called vernix caseosa. This "cheesy" substance, thought to protect baby's skin from long exposure to the amniotic fluid, is shed just before birth.
You may begin to feel your baby move, since he or she is developing muscles and exercising them. This first movement is called quickening.
By the end of the fifth month of pregnancy, your baby is about 25 cm (10 inches) long and weighs from 228 g to 454 g (1/2 to one pound).
Month six of pregnancy
By the end of the sixth month, your baby is about 30 cm (12 inches) long and weighs about 600 - 907g. His or her skin is reddish in colour, is wrinkled, and veins are visible through the baby's translucent skin. Baby's finger and toe prints are visible. The eyelids begin to part and the eyes open.
Your baby may respond to sounds by moving or increasing the pulse, and you may notice jerking motions if baby hiccups.
If born prematurely, babies can often survive after the 23rd week of pregnancy with intensive care.