A blood test conducted during the second trimester. The levels of AFP and estriol typically rise during the second trimester, while hCG decreases. Measuring all three levels gives information about the risk for birth defects such as Down syndrome, and neural tube defects like spina bifida. Optional test performed during second trimester, usually at between 15th and 18th week. After an ultrasound determines the position of the baby, a needle is inserted into the abdomen to remove a sample of amniotic fluid.
Analysis can detect neural tube defects and genetic disorders.
Amniocentesis is sometimes used later in pregnancy to determine fetal lung maturity in high-risk cases. The procedure carries a slight risk of infection or miscarriage. Optional test performed in the ninth to 11th week. A catheter inserted in the abdomen or vagina obtains a section of the placenta. As with an amniocentesis, analysis can detect neural tube defects and genetic disorders.