Pregnancy & prenatal testing: Second trimester
Alpha-fetoprotein (AFP) is produced by the baby and then crosses into the mother’s blood stream. A baby with a neural tube defect (NTD), such as spina bifida, has an opening in its spine, head or abdominal wall that allows an increased amount of AFP to pass into the mother’s blood stream. A raised AFP result in the mother’s blood at about 16 weeks of pregnancy is an indication that an NTD may be present, although it can also result from a twin pregnancy or be a result of a miscalculation of the gestational age.

Limitations of screening
Screening tests are not conclusive for the presence of a birth defect but indicate the possibility of a problem. Further tests must be performed to confirm the baby’s condition.

Related links
Tests: Maternal screeninghCGunconjugated oestriol
Conditions: Neural tube defects
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