Accuracy of dating pregnancy tests
During this time, your doctor will also take other blood tests (known as a triple screen or a quad screen) that will measure blood levels of alpha-fetoprotein, estriol, h CG (human chorionic gonadotropin), and inhibin, which can indicate whether the fetus is at risk for abnormalities such as Down syndrome or spina bifida.
A newer blood test, PAPPA (pregnancy-associated plasma protein A), conducted during weeks 10-14 of the pregnancy and used in conjunction with an ultrasound screening, is a good choice for women who are at risk of having a baby with a chromosomal abnormality, says Petrikovsky.
Another indication, he says, is simply whether you think you're pregnant.
Though these are all routine tests, there may be other prenatal tests that your obstetrician will recommend, depending on your racial or ethnic background or family medical history, says Vivian Weinblatt, MS, CGC, regional manager of genetic services for Genzyme Genetics in Philadelphia and former president of the National Society of Genetic Counselors.
Certain populations, for example, are at risk for certain diseases, Weinblatt explains.
A Pap smear -- if one has not been performed recently -- will be done to test for early cervical cancer and sexually transmitted diseases such as chlamydia and gonorrhea, while a urine specimen will be taken to check for urinary tract infections.
A blood pressure check will also screen for high blood pressure, which can interfere with the blood supply to the placenta.