Spina Bifida is a common type of Neural Tube Defect (NTD) that occurs when the spinal column does not close completely during early fetal development. Detecting the potential for this condition before birth relies on prenatal screening tests, which estimate the risk a developing baby may have for certain birth defects. Understanding the timelines for these screenings, from the blood draw to the delivery of results, can help manage the waiting period for initial Spina Bifida risk blood test results.
Maternal Serum Screening for Neural Tube Defects
The primary method for screening for Spina Bifida risk involves a maternal blood test called Maternal Serum Screening (MSS). This screening is typically performed during the second trimester of pregnancy, most accurately between the 16th and 18th weeks. This specific time frame is necessary because the levels of the measured substances change significantly, and the test calculation relies on precise gestational timing.
The test most often used to assess this risk is the Quad Screen, which measures four specific substances in the mother’s blood. One is Alpha-Fetoprotein (AFP), a protein produced by the developing baby that crosses the placenta into the mother’s bloodstream. High concentrations of AFP in the maternal serum are associated with a higher risk of an open neural tube defect, such as Spina Bifida.
This blood test serves as a screening tool, not a diagnostic one. Screening tests only indicate whether a pregnancy is at a higher or lower chance for a condition. A result indicating a higher risk simply means further evaluation is warranted.
Typical Result Turnaround Time
Results from the maternal serum screening test typically arrive within one to two weeks following the blood draw. This waiting period translates to about 5 to 10 business days for the laboratory to process the sample and calculate the risk assessment. The process requires careful analysis of the four measured markers, combined with factors like the mother’s age and gestational age, to provide an accurate risk estimate.
Several factors can influence this typical turnaround time. If the blood sample is processed by a local hospital laboratory, the results may be available sooner. However, many specialized maternal screening panels are sent to regional or centralized reference laboratories for analysis, which can add extra days for shipping and handling.
The communication chain also affects when the patient receives the final result. The laboratory first sends the report to your healthcare provider, such as your obstetrician or midwife. The provider’s office then reviews the results before contacting you, which can introduce a slight delay.
If the results indicate an elevated risk for a neural tube defect, providers may prioritize contacting the patient immediately. Normal, or “screen negative,” results are often communicated during a scheduled follow-up appointment or through an electronic patient portal. If you are experiencing anxiety, ask your provider at the time of the blood draw exactly when and how you should expect to receive the information.
Next Steps Following Screening Results
A “screen positive” result for Spina Bifida does not confirm a diagnosis, but signals the need for more specific diagnostic testing. An elevated AFP level suggests an increased probability of an open neural tube defect. Further testing is necessary because other factors, such as incorrect dating of the pregnancy or carrying multiples, can also cause high AFP levels. These diagnostic procedures provide a much clearer picture, allowing families and their care team to make informed decisions.
Level II Ultrasound
If the screening result is abnormal, the first follow-up procedure is typically a high-level, or Level II, ultrasound examination. This specialized imaging uses sound waves to create detailed pictures of the developing baby’s anatomy, including the spine and head. An experienced sonographer can often identify physical signs of Spina Bifida, such as an opening in the spine or specific changes in the brain structure, which provides a diagnosis with high accuracy. Ultrasound results are usually provided immediately, often during the appointment itself.
Amniocentesis
If the ultrasound results remain inconclusive or if a definitive diagnosis is required, the next step may be amniocentesis. This procedure involves using a thin needle to remove a small sample of the amniotic fluid surrounding the baby. The fluid is then tested for alpha-fetoprotein and acetylcholinesterase, which are accurate markers for an open neural tube defect. The results from an amniocentesis typically take about two weeks to be finalized.