Fetal Anomaly (Birth Defect) Information & Resources

What are fetal anomalies?

A fetal anomaly is a genetic or physical defect in the fetus that can affect pregnancy, complicate delivery and have serious adverse effects on the child. Fetal anomalies, often referred to as birth defects, are structural changes to one or more parts of the fetus’ body that increase the chance of stillbirth and can cause deficiencies in the child’s health, development and quality of life. Many women whose pregnancies are affected by fetal anomalies will consider terminating the pregnancy.

The Centers for Disease Control reports that about 120,000 pregnancies in the United States are affected by fetal anomalies each year. These cases vary greatly depending on the type of anomaly and the extent to which it affects the pregnancy. Fetal anomalies can range from minor issues that can be easily fixed, to severe issues that mean that the fetus will either be stillborn or die shortly after birth. If a pregnancy is affected by an anomaly found on a blood test or ultrasound, the woman might be referred to a high-risk pregnancy doctor for further testing and discussion.

What causes fetal anomalies?

Fetal anomalies, or birth defects, can occur at any stage during pregnancy and are believed to be the result of a number of factors including genetics and environmental issues such as exposure to chemicals or viruses. Many times, even with testing, we do not know what causes fetal anomalies to happen in a specific pregnancy.

Genetic, or inherited anomalies, can be passed from either mother or father without knowledge and can occur when cells combine at conception. If a woman or her partner are found to have a genetic cause of a fetal anomaly, they may be referred to a genetic counselor to discuss further testing or risk of recurrence.

Screening for fetal anomalies

Fetal anomalies can be diagnosed prior to birth, at birth or after birth. Through the course of a pregnancy, the doctor will perform screening tests to identify whether an increased risk of a fetal anomaly is present. Screening tests are not a formal diagnosis, and a screening test that indicates an abnormality will typically require additional testing.

First trimester

Between weeks 11 and 13, a doctor will likely perform a standard blood test and ultrasound. During this initial screening, doctors will measure the human chorionic gonadotropin (hCG) levels and pregnancy associated plasma protein A (PAPP-A) within the mother’s blood. If hCG or PAPP-A levels are too high or low, that can be an indication of a chromosomal disorder, such as Down syndrome. An ultrasound is also used to identify early signs of potential chromosomal disorders. An alternative to this standard testing is called NIPT, or non-invasive prenatal testing. This test looks at fetal cells found in maternal blood to screen for chromosomal disorders affecting the pregnancy.

Second trimester

A second trimester screening typically occurs between week 15 and week 20 and consists of a blood test and comprehensive ultrasound. This blood test, known as a maternal serum screen, can look at three to four different protein levels in the mother’s blood to identify an increased risk of certain structural or chromosomal anomalies. In addition to the blood test, a comprehensive ultrasound is performed to check for developing structural abnormalities in the fetus.

Diagnosing fetal anomalies

If a screening test comes back with abnormal results, in order to determine if an anomaly is actually present doctors will offer a diagnostic test such as a high-resolution ultrasound, chorionic villus sampling or amniocentesis (see below). Diagnostic tests are also offered to women carrying higher-risk pregnancies due to advanced maternal age, previous pregnancies affected by fetal anomalies, chronic diseases or other medical conditions.

High-resolution ultrasound

Advanced ultrasound imaging allows doctors to examine the pregnancy with greater detail, enabling them to better identify potential structural abnormalities that previous screening tests indicated.

Chorionic villus sampling (CVS)

This test is typically completed between weeks 10 and 12 of pregnancy and offered to women who received an abnormal screening result in their first trimester. Doctors will collect a sample of the placenta, known as the chorionic villus, and test it for the markers of chromosomal or genetic disorders.


An amniocentesis is also performed after an abnormal screening result and is typically completed between 15 and 18 weeks of pregnancy. During an amniocentesis, a doctor will collect a small amount of amniotic fluid and measure the protein levels within the fluid that might indicate an anomaly. For example, if an analysis shows high levels of alpha-fetoprotein (AFP) in the amniotic fluid, this may be an indication of an opening in the tissue such as a neural tube anomaly. They can also test fetal cells in the amniotic fluid to look for genetic disorders.

Fetal echocardiography

Fetal echocardiograms are typically performed between 18 and 24 weeks of pregnancy if a potential structural abnormality or abnormal heartbeat were present in an ultrasound. Fetal echocardiograms use ultrasound technology to develop a detailed image of the heart to help doctors determine if the complex structures of the heart have developed and are working properly.

After diagnosis

The overall aim of fetal anomaly screening and diagnostics is to identify potential problems with the pregnancy so that women and their partners can take informed next steps to improve the safety of the pregnancy. There are a number of factors to consider and discuss with a medical professional after a diagnosis, including the medical benefits of abortion.

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Additional Resources

The sites included here are non-denominational, non-judgmental sites that include information and links for parents who are dealing with the diagnosis or aftermath of a fetal anomaly.

A Heartbreaking Choice

Resources and support for families who have terminated a pregnancy following prenatal diagnosis.

A Place to Remember

Support materials and resources for those who have been touched by a crisis in pregnancy

Genetic Alliance

Resource for parents of children with rare genetic disorders.

MISS Foundation

Provides immediate and ongoing support to grieving families, empowerment through community volunteerism opportunities, public policy and legislative education, and programs to reduce infant and toddler death through research and education.

Mountain States Genetics Network

Lists prenatal counseling and genetics services in AZ, CO, NM, UT, and WY. Has a large list of online resources for fetal anomalies.

Pen-Parents, Inc.

A network connecting bereaved parents so they can correspond with others who have experienced a similar type of loss. Offers interactive website.