Who Should be Offered 2nd Trimester Screening?
Maternal blood screening is designed for pregnant women who are at low risk for the disorders being screened. Therefore, the screening programs described here are for women who are under 35 years of age at the time of delivery and who do not have a positive history of an ONTD or chromosome abnormality. High-risk patients should be referred for genetic counseling, ultrasound, and amniocentesis. High-risk patients are those who are 35 years or older at delivery, have a close relative with an ONTD (self, spouse, child, parent or sibling) or have a previous child with a chromosome abnormality. 1st and 2nd Trimester blood screening should not be provided to high-risk patients (women over 34 years of age at EDD or with a positive medical history) as a substitute for amniocentesis chromosomal analysis because: • Screening provides a risk for two out of the hundreds of types of chromosome abnormalities, not a diagnosis, whereas amniocentesis can diagnose 99.99% of the hundreds of types of feta
