Glossary
| Term | Description |
|---|---|
| Alpha-fetoprotein | Alpha-fetoprotein (AFP) is a protein produced mainly in the developing baby's liver and released into the amniotic fluid. A small amount crosses the placenta and can be measured in a pregnant woman's blood towards the end of the first trimester. Levels rise at a steady rate throughout the second trimester. In most babies affected with open spina bifida, anencephaly, or an abdominal wall defect, more AFP is in the amniotic fluid and that leads to a higher amount of AFP in the maternal blood. In Down syndrome, trisomy 18, and SLOS, AFP levels may be lower than average. |
| Anencephaly | A condition in which the skull cap and brain do not develop. |
| Neural tube | The organ which becomes the baby's brain and spinal cord. Completely formed by 5 weeks after conception. If the neural tube does not develop properly, birth defects such as spina bifida, anencephaly, and encephalocele can occur. |
| Neural tube defect | Birth defects which involve incomplete development of the brain, spinal cord and/or the protective coverings for these organs. Types of NTDs include spina bifida, anencephaly, and encephalocele. |