An ultrasound creates pictures of the baby. This test is usually completed around 18–20 weeks of pregnancy. The ultrasound is used to check the size of the baby and looks for birth defects or other problems with the baby.
High-frequency transvaginal ultrasound screening with 3D/4D technology can provide a definitive diagnosis in cases with certain fetal defects, such as acrania and conjoined twins. In others, a diagnosis may be suspected at 6–10 weeks and subsequently confirmed at 11–14 weeks or later in pregnancy.
Identifying Birth Defects
Some birth defects (such as cleft lip) are easy to see, but others (such as heart defects or hearing loss) are found using special tests, such as echocardiograms (an ultrasound picture of the heart), x-rays or hearing tests.
You may have prenatal tests (medical tests you get during pregnancy) to check your baby for birth defects. These may include screening tests and diagnostic tests. A screening test is a medical test to see if you're at risk or if your baby is at risk for certain health conditions, like birth defects.
Accuracy in Detecting Birth Defects
Congenital defects, both major and minor, occur in around three percent of all births. Of these, roughly three out of four will be detected by ultrasound. The accuracy of these tests, however, is closely related to the stage and type of pregnancy involved.
Every 4 1/2 minutes, a baby is born with a birth defect in the United States. Birth defects affect 1 in every 33 babies born in the United States each year. That translates into about 120,000 babies.
MRI helps diagnose fetal brain abnormality after 20 week scan, study finds. The study included 570 women aged over 16 whose ultrasound scan at around 20 weeks of pregnancy suggested a brain abnormality in their developing fetus. This is relatively common, occurring in around three in 1000 pregnancies.
Most 12-week ultrasounds show that babies are developing well, but sometimes they pick up chromosomal anomalies or other problems. Some of these problems aren't serious and won't need much, if any, treatment. But some are signs of serious disability.
Are all birth defects discovered before a baby is born? It's not always possible to detect all birth defects in utero. However, high-resolution ultrasounds done by certified prenatal ultrasound groups make it possible to diagnose defects that will cause a significant impact before birth.
The first trimester is the most crucial to your baby's development. During this period, your baby's body structure and organ systems develop. Most miscarriages and birth defects occur during this period. Your body also undergoes major changes during the first trimester.
Major abnormalities of the fetal head, abdominal wall and urinary tract, and of the umbilical cord and placenta, can be reliably detected at 10-11 weeks of gestation. Detection of other anomalies such as spina bifida, diaphragmatic hernia or heart defects is limited before 13 weeks of gestation.
Most birth defects happen during the first 3 months of pregnancy. One out of every 33 babies in the United States is born with a birth defect. A birth defect may affect how the body looks, works, or both. Some birth defects like cleft lip or neural tube defects are structural problems that can be easy to see.
First trimester screening is a combination of fetal ultrasound and maternal blood testing. This screening process can help determine the risk of the fetus having certain birth defects. Second trimester prenatal screening may include several blood tests called multiple markers.
Stress results in increased catecholamine production, which in turn leads to decreased uterine blood flow and increased fetal hypoxia. Animal studies indicate that hypoxia affects a variety of developmental processes (eg, cell death)29 and organ systems, which could result in various types of birth defects.
“A review of over 50 medical studies shows that ultrasounds do not pose any danger to moms or fetuses. They do not cause birth defects, childhood developmental or intellectual problems, or cancer.”
Fetal structural abnormalities at the 11-14 week scan were detected in approximately 22.3% of the cases, therefore, a second-trimester anomaly scan is important in routine antenatal care to increase the prenatal detection of fetal defects.
A 20-week ultrasound doesn't find all congenital conditions. However, the scan can help detect several serious conditions: Anencephaly. Indicators for Down syndrome or trisomy 18 and trisomy 13.