13 Weeks- Development

Your Baby This Coming Week

Your baby measures about 3.2 to 3.5 inches (7.6 to 8.9cm) from crown to rump and weighs about 0.9 ounces (25g). Your baby is now nourished by the placenta.

His face is developing and his cheeks and the bridge of his nose are appearing. His ears are moving from the sides of his neck to higher on his head and his eyes are moving closer together. Your baby's external genitals are now distinct and may be recognized on an ultrasound. Your baby will move away from stimuli near your tummy, such as noise and light.

Your baby's eyebrows have formed and a small amount of hair, called lanugo, has appeared all over his body. Lanugo, which will be shed before birth and replaced with the hairs with which your baby will be born, is thought to have a protective function.

Insulin is present in your baby's pancreas. Some bones may be well outlined. Your baby's thyroid gland, already developed by this week, begins to make hormones.

Baby boys begin to develop the prostate gland at this time and the ovaries of baby girls descend from the abdomen into the pelvis.

Your Body This Coming Week

By now your uterus is about the size of a large grapefruit. If your due date has not already been predicted, an ultrasound measurement of your baby's head can be used to make one.

Your pre-pregnancy clothes are probably too tight by now. If you haven't already got some maternity clothes, now is probably the time to get some. You'll be most comfortable in loose-fitting clothes. Make sure you really like your maternity clothes- you'll be wearing them a lot. Friends, family and thrift shops can be a great source of maternity clothes.

You may feel less exhausted than you did earlier in your pregnancy. Some women even start to experience a rejuvenating surge of energy at around this time. Many women report that the second trimester is the best time of pregnancy as the morning sickness of the first trimester has usually passed, and the discomforts and weariness of the third trimester have yet to begin. If you would like to take a last holiday before your baby arrives, the second trimester, with your doctor's approval, is probably the best time to do so. This could be a good opportunity for you and your partner to connect and share some couple-time before the baby arrives.