If you think you might be pregnant, you can use a home pregnancy test as soon as the first day of your first missed menstrual period. Pregnancy is measured in weeks from the first day of your last menstrual period (LMP). There are several ways to calculate how long you have been pregnant. You can also use your LMP to calculate your due date.

As soon as you know you're pregnant, make an appointment with your doctor or certified nurse-midwife (CNM). Your first prenatal visit will provide information that can be used to check for any problems as your pregnancy progresses.

Good care during pregnancy includes regularly scheduled prenatal exams. At each prenatal visit, you'll be weighed, have your abdomen measured, and have your blood pressure and urine checked. Use this time to discuss your list of pregnancy concerns or problems with your health professional. At different times in your pregnancy, you will have additional exams and tests performed. Although some are routine, others are only done when a problem is suspected or if you have a risk factor for a problem.

First prenatal visit exams and tests include a health history, physical examination, and blood and urine tests.

First-trimester exams and tests may include fetal ultrasound, which uses reflected sound waves to provide an image of your fetus and placenta. The late first trimester is the earliest time when you can have the newer, noninvasive Down syndrome screening using a blood test and an ultrasound measurement of fetal neck (nuchal fold) thickness. (Nuchal fold ultrasound is not yet widely available, because only a specially trained provider can do it.) This is also when you can have genetic testing of your placenta (chorionic villus sampling, or CVS). A CVS gives you earlier results than a second-trimester amniocentesis. Only a highly trained provider can do a CVS.

Second-trimester exams and tests may include fetal ultrasound and electronic fetal heart monitoring. In the early second trimester, you can have the triple or quadruple screen. This screen measures your blood levels of:

• Alpha-fetoprotein (AFP).
• Human chorionic gonadotropin (hCG).
• Estrogen (estriol).
• Inhibin A (quad screen only).

If you are at risk for genetic problems or your triple or quad screen says your fetus might have a problem, you may have testing of the fluid surrounding your baby (amniocentesis). Later on in the second trimester, you will have an oral glucose screen for possible gestational diabetes.

If you have Rh negative blood, you may have an antibody screen and will receive an injection of Rh immune globulin.

Third-trimester exams and tests may include fetal ultrasound, hepatitis B, and group B strep screening.

All pregnant women should be screened for human immunodeficiency virus (HIV) infection to help prevent newborn HIV infection.⁴ Some health professionals may not order this test unless you request it.

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