A pregnant woman can undergo fetal screening for certain birth defects as she nears the end of her first trimester. The first test is called nuchal translucency screening, and it is done between 11 and 14 weeks of pregnancy. The doctor uses ultrasound to measure the thickness of fluid buildup on the back of the baby’s neck. If the buildup is abnormally thick, it can indicate a birth defect like heart problems, Down syndrome, or trisomy 18.
First trimester screening can only indicate the possibility of a problem existing; it does not definitely mean there is a problem. Nor does it diagnose the type of birth defect. Therefore, if the screening does indicate a possible birth defect, the woman will need to undergo a diagnostic test like amniocentesis to make certain.
What are trisomy 18 and Down syndrome?
Trisomy 18 is a genetic condition caused by the presence of an extra chromosome 18. Human beings normally have 23 pairs of chromosomes, but sometimes something goes wrong very early in development that results in a third chromosome 18. Trisomy 18 condition is usually lethal to the developing fetus, but some do survive to be born. These survivors suffer mental disabilities and have heart and kidney defects. They also have a malformed chest, a small head with low set-ears, and crossed legs.
Down syndrome or trisomy 21 is also a genetic condition caused by an extra chromosome. People with the condition have distinctive facial features, most notably a flat nose and obliquely set eyes. They either are born with or risk developing health problems that affect the respiratory system, thyroid gland, heart, ears, or gastro-intestinal tract. Nonetheless, many people with Down syndrome can become self-sufficient.
The second screening method used is first trimester blood tests. The doctor draws the mother’s blood and measures the amounts of two substances in it: human chorionic gonadotropin (beta-hCG) and pregnancy-associated plasma protein A (PAPP-A).
Abnormally low levels of beta-hCG indicate an ectopic pregnancy, in which the fertilized egg has implanted somewhere outside the uterus. They can also indicate a miscarriage. Unusually high levels of beta-hCG indicate the possibility of a multiple pregnancy like twins or triplets. A high level of beta-hCG may also indicate Down syndrome or a molar pregnancy. Abnormally low levels of PAPP-A may also indicate birth defects, including Down syndrome and trisomy 18.
What is a Molar Pregnancy?
A molar pregnancy is caused by an abnormal growth of placental cells in the uterus that triggers the signs of pregnancy. In a complete molar pregnancy, the whole uterus can be filled with a tissue mass. In a partial molar pregnancy, the placental cells may be accompanied by extremely abnormal fetal tissue. All of this tissue must be removed, or the woman could develop cancer.
At SouthLake OB/GYN in Clermont, we specialize in women’s health through all phases of life. We strive to keep expectant mothers and their developing babies safe and healthy. We will work with you every step of the way to ensure you are comfortable as well as well informed. Our medical team is available to answer any questions you may have. Contact SouthLake OB/GYN today to schedule your consultation.