You may still be feeling the early symptoms of pregnancy, but these should disappear shortly. Your waist line may now start to grow a little. Toes, ears and the upper lip are now formed, and external genitalia will start to form this week. By the end of this week, your baby’s vital organs have been formed and are starting to work together. Brain growth increases rapidly by this week - almost 250,000 new neurons are produced every minute in your baby’s brain! As external changes take place, internal developments are occurring too. Tooth buds form inside the mouth. If you’re having a boy, his testes will begin producing the male hormone, testosterone. Congenital abnormalities are unlikely to develop after week 10. This week also marks the end of the embryonic period, so your baby is officially considered a fetus.
Around this time, your doctor will probably send you for a blood test to find out whether you are immunized against varicella, measles, mumps and rubella (German measles). This blood test will also determine your blood type and Rh factor. Rh factor is a substance found in the red blood cells of most people. If you don’t have it (Rh negative) but your baby does (Rh positive), complications can result when the baby’s blood cells enter your bloodstream. Your doctor can prevent Rh incompatibility problems by giving you a vaccine of Rh-immune globulin at 28 weeks and again after delivery.
Revision date: June 22, 2011
Last revised: by Sebastian Scheller, MD, ScD