AFP and Down syndrome: Among these biomarkers are alpha-fetoprotein (AFP), used to assess the baby’s risk of birth abnormalities and genetic conditions such as Down’s syndrome and neutral tube defect during pregnancy; cytokeratin 19 fragment (cyfra 21-1), a serum marker for detecting lung cancer, oesophageal cancer, head and neck cancer, anal canal cancer and gynaecological cancer, and cancer antigen-125 (CA125), an antigenic tumour marker that can diagnose or monitor ovarian, fallopian tube or primary peritoneal cancer.