By Joanne Stone, Keith Eddleman, Mary Duenwald

Although you won’t be feeling it this early, this is the time when your baby starts to move around. If you’re having an ultrasound at this time, you may actually see these movements on the screen. Before 10 weeks, male and female embryos look the same.

After 10 weeks, their external genitalia start to develop differently, although your practitioner may not be able to see this difference on ultrasound until after 14 to 15 weeks. By the end of the tenth week, all the organ systems have formed. The brain is unique in that it continues to develop throughout pregnancy and even into childhood.

You want to consider the following counseling and testing at this time:

  • Schedule an appointment for genetic counseling if you have a family history of genetic problems. Your doctor may also recommend it depending on varying circumstances.

  • Make sure you schedule your first trimester screen for Down syndrome. Remember, the best time to do this is at 11 to 12 weeks. This is a combination of measuring a fluid-filled region behind the fetal neck called a “nuchal translucency,” which is combined with your age and blood tests (hCG and PAPPP-A) and gives a specific risk for Down syndrome, as well as Trisomy 13 and 18 (and extra chromosome 13 and 18).

    Talk to your provider to see if he thinks you are a candidate for a different type of screening for Down syndrome by one of the newer tests that extracts fetal genetic material from your blood. This blood sample can be drawn as early as 9 weeks.

  • If you’re considering having a chorionic villus sampling (CVS), weeks 10 to12 are the best time to do this.

At the end of week 12, your baby is 2.13 inches (5.4 mm) long and weighs less than half an ounce (around 14 g). Your uterus is the size of a large orange.