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Prenatal Screening Tests in First Trimester
Pregnancy is one of those amazing times in a couple's life. Your new baby and its potential are growing as we speak. And a new sense of responsibility is also rising in the background; you are going to be making some decisions that may ultimately affect your baby.

As an obstetrician counseling couples and a father of three, I understand and respect couples' beliefs and fears. But I also know that there are some excellent tests available to help ensure the health of your baby. Some of these tests are routinely ordered for every couple, while others are selectively offered to those of various ethnic backgrounds or genetic histories. For example:
  • Caucasian couples should be screened during pregnancy to find out if they're carriers of the genetic traits for Cystic Fibrosis (see my article on Cystic Fibrosis).
  • Couples of Ashkenazi Jewish origin should consider a series of tests collectively known as the Jewish Heritage Profile. If only one member of the couple is Jewish, they should be screened first. This panel of eight tests helps detect carriers of various genetic diseases which can cause life-long difficulties for the child. Cystic Fibrosis, Tay-Sachs, Gauchers, Canavans, Nieman-Pick, Bloom, Familial Dysautonomia, and Fanconi's Anemai are included in this screening. If you have questions, ask your obstetrician for more information on these diseases.
  • Couples of African origin should be screened for sickle cell trait. This common genetic variant is easily determined during the initial blood tests for the woman. If she is a carrier, her partner should undergo screening. Two carriers of sickle cell trait have a 75% chance of having a normal baby. To determine if your baby is affected, an amniocentesis or chorionic villus (CVS) sampling should be performed, and the results discussed with your obstetrician.
  • Couples of Italian or Mediterranean descent should be screened for thalassemia. This inherited disorder can be easily screened in the initial bloodwork performed on the woman. An abnormal test is followed by more specialized testing. For those who carry the gene, their partner should also be tested. When both partners carry the gene, CVS or amniocentesis will determine the child's status; 75% of the babies are normal in this situation.
  • Couples of Asian or Indian descent should also be screened for a different type of thalassemia. Once again, the initial bloodwork performed on the woman screens for the disease. An abnormal test result is followed by more specialized testing. For those who carry the gene, their partner should also be tested. When both partners carry the gene, CVS or amniocentesis will determine the child's status; 75% of babies are normal in this situation.


Even if you or your partner is a positive carrier for one of these diseases, it doesn't mean your baby will have the illness. It is important to understand that you both must carry the same gene for there to be any possibility of passing these conditions on to your baby. That's why I ask the second partner to have screening in this situation. If both carry the same genetic trait, you still have a 75% chance of having a healthy child. To finally determine if your baby is affected, an amniocentesis or chorionic villus (CVS) sampling should be performed. Then you should carefully discuss the results with your obstetrician.

If you are a parent-in-waiting who does carry one of these genes, you will not develop the disease yourself. However, you should notify your siblings so they can determine their genetic status.

Pregnancy is filled with so many great expectations. As your guide through this exciting time, we obstetricians try to help you select the best ways to ensure a healthy and happy new addition to your family. Prenatal testing is just one of the ways we can help you in this process, but it may not be for everyone (see my article titled “Prenatal Testing: Is it for you?”). By offering these early tests, our hope is to give you timely advice to help you realize your dreams.
Craig L. Bissinger M.D.