Weeks 13–16 of Your Pregnancy - dummies

By Joanne Stone, Keith Eddleman, Mary Duenwald

Congratulations! You and your baby made it through the first trimester. You’re starting to feel more like yourself — you have more energy and less nausea. After week 14, the majority of the amniotic fluid surrounding your baby is made up of the baby’s urine.

By week 15, an experienced sonographer can tell by ultrasound whether you’re having a boy or a girl. By week 16, your baby starts to grow fine, soft hair (called lanugo) and fingernails.

The following considerations apply during this time period:

  • Between weeks 15 and 18, have your blood drawn to check the alpha-fetoprotein (AFP) level. This blood test helps to identify fetal abnormalities such as spina bifida. This is also the time to have the second part of your Down syndrome screening (quad screen).

  • Schedule your amniocentesis between weeks 16 and 18 if you’re planning on having one.

  • Consider shopping at a maternity store. Many women start to show at this time. If you aren’t showing, don’t worry because some body types hide pregnancy better than others.

At the end of week 16, your baby is 4.6 inches (11.6 cm) long and weighs about 3-1/2 ounces (100 g). Your uterus is the size of a large grapefruit.