Prenatal screening is a way to determine whether or not a baby may have trisomy 21 (Down syndrome) or trisomy 18.
Similarly, it is a method used to:
- Confirm a pregnancy.
- Determining gestational age: A “normal” pregnancy is popularly thought to be 40 weeks gestation, but in medical terms, a full-term pregnancy is between 37 and 41 weeks. It is important to verify the gestational age of the developing fetus for several reasons. For example, the baby's growth will be measured using well-established growth charts to ensure normal development. Gestational age will be verified with the dates provided by the mother regarding her last menstrual period to confirm the due date and ensure delivery is not too early or too late.
- Check for multiple pregnancies (twins, triplets, etc.): A pregnancy with multiple babies carries special risks and should be checked regularly. Complications such as “twin-to-twin transfusion” and cervical incompetence require immediate attention if complications are to be avoided.
- Problems with the placenta: During pregnancy, the position of the placenta inside the uterus can be of vital importance for the health of both the baby and, in some circumstances, the mother. An ultrasound can determine complications in the placenta.
- Check the fetal position: During labor it can be important to know the position of the baby (breech, transverse, cephalic or optimal) because it can affect the method of delivery.
- Check for birth defects: Many parents will want to know if their baby has any congenital or genetic problems so that they can terminate the pregnancy or prepare for the difficulties associated with the particular problem.
- Monitor fetal growth: If the baby's growth is out of the expected range, this may be an indication of problems with the placenta and/or problems with the baby's health. Either way, early intervention may be required to treat the problem.
- Check the level of amniotic fluid: The fetus produces amniotic fluid and too much or too little amniotic fluid can be indicative of problems with the pregnancy that may require intervention.
- Helps in other tests: Tests like amniocentesis can be done much more safely when guided by ultrasound.
El Dr. Daniel García, gynecologist and obstetrician at Ginefem, explains why prenatal ultrasounds are done.