1st Trimester
At your first prenatal visit, the following lab tests are usually performed: urine analysis and/or culture, Pap smear, 
cultures for gonorrhea and chlamydia, blood typing and Rh antibody screening, a complete blood count, rubella (German measles) antibody, hepatitis B antigen, syphilis screen (required by New York State) and HIV screen (required by New York State on either the mother while pregnant or the newborn before release from the hospital).
Other tests that may be indicated include parvovirus (fifth disease) screen, toxoplasmosis screen if cats are in the household, Lyme disease screen and nuchal translucency screen for Down syndrome. At subsequent visits, a urine dip is usually done to check for signs of an infection, excess protein or excess sugar.
2nd Trimester
Early in the second trimester (16-18 weeks) maternal serum screening can be performed. This blood test is used as a screen for open neural tube defects like spina bifida. This test includes alpha-fetoprotein (AFP) and is optional.
Mid-pregnancy (18-20 weeks), an ultrasound or sonogram is usually performed to evaluate the baby's anatomy and to screen for birth defects.
3rd Trimester
Non-stress testing using an external fetal monitor is sometimes performed in the third trimester for patients with:
- Diabetes
- Hypertension
- Unexplained abnormal serum screening
- Post dates
Sonograms may also be performed in the third trimester to evaluate the baby's growth, the position of the placenta or the amount of amniotic fluid.