How are Pregnancies Evaluated for Chromosome Abnormalities?
First Trimester Ultrasound Evaluation For this evaluation, ultrasound is performed between 11 and 13 weeks 6 days. Evaluation of the developing fetal neck, nasal bone and blood flow measurements can be used to calculate a risk for common chromosome abnormalities. Information regarding the results of the ultrasound are calculated and patients are counseled regarding the results at the time of the appointment. First Trimester Maternal Serum Screening Testing for two proteins (bHCG and PAPPA) in the mother’s blood can assess the risk for common chromosome abnormalities. This testing may be added to ultrasound information, or done separately if ultrasound information cannot be obtained. Results of this test usually take about a week. Second Trimester Maternal Serum Screening This blood test is performed at 16 to 20 weeks of pregnancy. It may be added to the first trimester ultrasound and maternal serum screening, or performed separately if the patient did not have first trimester testing.
