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Your Pregnancy Week by Week: Weeks 13-16

Week 13

Baby: Your fully formed fetus, now in about its 11th week of development, measures 2.6 to 3.1 inches from crown to rump and weighs between half an ounce and seven-tenths of an ounce -- about the size of a peach. The head is still disproportionately bigger than the body, but the rest of the body is starting to catch up. In fact, your baby is growing rapidly these days. The face is starting to look more human, with eyes moving closer together. Toes and fingers are clearly separate, and ankles and wrists have formed. External genitalia are becoming visible. Intestines are shifting into their proper place, too.

Mom-to-be: Your uterus has grown a lot. It's filling your pelvis now and starting to grow upward into your abdomen. It probably feels like a soft, smooth ball. If you haven't put on any weight yet because of morning sickness, you'll begin to now as you start to feel better.

Pregnancy Week by Week

If you are newly pregnant, or trying to conceive, you have many questions about what to expect. How will your body change? What's happening inside you? Here's what to expect week by week.

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Tip for the Week: It's easy for your partner to feel left out of the pregnancy since he isn't feeling the same physical changes that you are. Both of you should share your excitement about having a child, your dreams, worries and your partner's level of involvement. Suggest that your partner goes to a check-up with you to hear the baby's heartbeat.

Week 14

Baby: Your baby measures about 3.2 to 4.1 inches from crown to rump now and weighs almost an ounce. The ears are shifting from the neck to the sides of the head, and the neck is getting longer and chin more prominent. Facial features and unique fingerprints are all there. Your baby is beginning to respond to outside stimuli. If your abdomen is poked, the fetus will try to wriggle away.

Mom-to-be: You're probably wearing maternity clothes now. Your skin and muscles are starting to stretch to accommodate your growing baby. You may notice some constipation because pregnancy hormones relax the bowel.

Tip of the Week: Try to alleviate constipation with moderate exercise, and by drinking plenty of fluids and eating lots of fruit and vegetables, preferably raw.

Week 15

Baby: Your 13-week-old fetus now measures about 4.1 to 4.5 inches from crown to rump and weighs about 1.75 ounces. Its body is covered by an ultrafine hair, called lanugo, which is usually shed by birth. Eyebrows and hair on the top of the head are beginning to grow. He may even be sucking his thumb by now. Bones are getting harder.

Mom-to-be: Your uterus can probably be felt about 3 to 4 inches below your navel. Sometime in the next five weeks you'll be offered a quadruple marker screening test, which measures four chemicals in your blood -- alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), inhibin A, and estrogen produced by the placenta. The test is a more accurate predictor of Down syndrome than AFP testing alone. Amniocentesis, which tests a small sample of amniotic fluid withdrawn by an ultrasound-guided needle, is usually performed between now and 18 weeks. It may be recommended if you're 35 or older or if your AFP or quadruple marker screen test results were suspicious.

Tip of the Week: Start learning to sleep on your left side because circulation is best that way. Lying on your back or stomach after about the fourth or fifth month can put extra pressure on your growing uterus and decrease circulation to your baby. You can try tucking pillows behind you and between your legs. Some manufacturers make a pregnancy pillow that supports your entire body.

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