Spina bifida is a type of neural tube defect. The neural tubes form in an embryo, close up by the end of the first month of pregnancy, and become the brain, spinal cord, and surrounding tissues—called meninges. When part of the neural tube does not close, one of the four types of spina bifida (occult, closed neural tube defect, meningocele, and myelomeningocele—from least to most severe) is present, resulting in anything from no symptoms to paralysis. Here is a look at how spina bifida is diagnosed.
Ultrasound
During pregnancy, the mother makes monthly visits to an obstetrician (doctor who specializes in pregnancy and delivery) until near time for delivery— then visits start becoming more frequent. Throughout the process, your doctor or an imaging technician will perform ultrasounds to ensure the pregnancy is developing normally. An ultrasound uses bouncing sound waves to create a black and white picture moving in real time of what’s going on internally, allowing you to see your baby while still in the womb.
During the second trimester, around the end of the fourth month and beginning of the fifth, the ultrasound is used to look for specific issues, spina bifida among them (these tests are most accurate between the 16th and 18th week of pregnancy). These fetal experts are trained to note any abnormalities that may be visible. However, in some cases, it may be so mild as to not be noticeable. Certain other fetal tests may indicate when it is necessary to perform an ultrasound to look specifically for spina bifida.
MSAFP Test
Maternal serum alpha-fetoprotein test (MSAFP test) is a screening test that can tell your obstetrical team if there might be something going on that requires further investigation for the health of both mother and baby. Blood is drawn from the mother and tested by a laboratory for the fetus produced protein, alpha-fetoprotein. Extremely high levels can be indicative of the presence of a neural tube defect, such as spina bifida.
While high levels suggest a need for further testing (like the ultrasound), it does not necessarily mean there’s a problem. If the time since conception is incorrect or there are multiple babies, these levels may be different. Additionally, there may not necessarily be a neural tube defect. There could also be a mild defect and low levels of AFP that don’t tip off doctors to its presence. Other blood tests may also be utilized.
Amniocentesis
Amniocentesis is another form of diagnostic testing; a small amount of amniotic fluid that surrounds the baby is extracted from the uterus. While not every woman will receive this test, those with higher risks of fetal abnormality will: mothers over the age of 35, positive results from previous screening tests, genetic abnormalities in other children or immediate family, or abnormal ultrasound results, among other things. While your insurance may not cover this test, if you’re concerned you can always request amniocentesis.
High levels of AFP will be detected in this diagnostic test as well, because the open neural tubes leak into the amniotic fluid, undeterred by a barrier of skin. If you’re concerned about the results of your screening tests or carry a predisposition to neural tube defects, talk to your doctor about the risks and benefits of performing amniocentesis.