Diagnosis

If you're pregnant, you'll be offered prenatal screening tests to check for spina bifida and other birth defects. The tests aren't perfect. Some mothers who have positive blood tests have babies without spina bifida. Even if the results are negative, there's still a small chance that spina bifida is present. Talk to your doctor about prenatal testing, its risks and how you might handle the results.

Blood tests

Spina bifida can be screened with maternal blood tests, but typically the diagnosis is made with ultrasound.

• Maternal serum alpha-fetoprotein (MSAFP) test. For the MSAFP test, a sample of the mother's blood is drawn and tested for alpha-fetoprotein (AFP) — a protein produced by the baby. It's normal for a small amount of AFP to cross the placenta and enter the mother's bloodstream. But abnormally high levels of AFP suggest that the baby has a neural tube defect, such as spina bifida, though high levels of AFP don't always occur in spina bifida.
• Test to confirm high AFP levels. Varying levels of AFP can be caused by other factors — including a miscalculation in fetal age or multiple babies — so your doctor may order a follow-up blood test for confirmation. If the results are still high, you'll need further evaluation, including an ultrasound exam.
• Other blood tests. Your doctor may perform the MSAFP test with two or three other blood tests. These tests are commonly done with the MSAFP test, but their objective is to screen for other abnormalities, such as trisomy 21 (Down syndrome), not neural tube defects.

Ultrasound

Fetal ultrasound is the most accurate method to diagnose spina bifida in your baby before delivery. Ultrasound can be performed during the first trimester (11 to 14 weeks) and second trimester (18 to 22 weeks). Spina bifida can be accurately diagnosed during the second trimester ultrasound scan. Therefore, this examination is crucial to identify and rule out congenital anomalies such as spina bifida.

An advanced ultrasound also can detect signs of spina bifida, such as an open spine or particular features in your baby's brain that indicate spina bifida. In expert hands, ultrasound is also effective in assessing severity.

Amniocentesis

If the prenatal ultrasound confirms the diagnosis of spina bifida, your doctor may request amniocentesis. During amniocentesis, your doctor uses a needle to remove a sample of fluid from the amniotic sac that surrounds the baby.

This examination may be important to rule out genetic diseases, despite the fact that spina bifida is rarely associated with genetic diseases.

Discuss the risks of amniocentesis, including a slight risk of loss of the pregnancy, with your doctor.