Week 12

week_12During your first trimester, your physician will recommend blood testing that evaluates you and your baby for a condition known as Rh incompatibility.

This condition occurs when a mother has Rh negative blood while baby’s is positive, which can result in pregnancy complications if left undiagnosed.

Understanding Rh

An estimated 85 percent of people have Rh, a protein that is found on the red blood cells. If you have Rh, you are considered Rh positive; however, some people do not have the Rh protein. If you are Rh negative and the father of your baby is Rh-positive, this could result in an incompatible match.

As an expectant mom, you share more than a body with your baby—you also share blood that filters to your baby through the placenta. If your Rh status does not match up, your body may begin making antibodies. While this isn’t a concern during a woman’s first pregnancy, it could affect future pregnancies.

During the 12-week testing, your physician will perform a blood test that can determine if you are Rh negative. Treatments, such as Rh immunoglobulin injections, can prevent antibodies from developing and ensure you continue to experience a healthy pregnancy. Many physicians will administer this shot at 28 weeks and then immediately following birth.

Seeing Your Baby Clearly

While you may consider your ultrasound exam as an opportunity for you to view your growing baby, your physician uses the ultrasound to measure the thickness at the back of baby’s neck. This exam is known as a nuchal translucency screening and can help your physician identify possible birth defects. At this time, a physician may examine your ultrasound for signs of conditions such as Down syndrome, trisomy 18 or other chromosomal abnormalities.

A woman’s risk of chromosomal defects is then calculated using the combined results of the blood test and ultrasound. According to the American College of Obstetricians and Gynecologists, first trimester screening can detect about 82 percent to 87 percent of Down syndrome cases.


  • During the third month of pregnancy, fathers-to-be may also experience pregnancy symptoms known as couvade or “hatching.” Symptoms include nausea, abdominal pain, weight gain and changes in appetite; these can continue throughout the pregnancy.
  • According to the American College of Obstetricians and Gynecologists, only two or three in 100 newborns will have major birth defects.