First-trimester exams and tests

Routine exams

At each prenatal visit, you'll be weighed and have your urine and blood pressure checked. Your health professional will monitor your fetus's growth by measuring the height of your uterus (fundal height) above your pubic bone.

Using a Doppler ultrasound, you should be able to hear your fetus's heartbeat as early as weeks 10 to 12. By the 20th week, the fetal heart tone is strong enough to hear with a specialized stethoscope (fetoscope).

Additional testing

If you are worried about birth defects, talk to your health professional about birth defects screening and testing options.

• Although not yet widely available, you may be able to consider a combination of first-trimester screening tests to look for possible Down syndrome. The screening combines ultrasound measurement of the thickness of the fetus's neck (nuchal fold) and measurements of beta-human chorionic gonadotropin (beta-hCG) and a protein called pregnancy-associated plasma protein A (PAPP-A). This screening is about as accurate as the second-trimester maternal serum quadruple screening.¹
• Chorionic villus sampling (CVS) is a diagnostic test that can be used to detectDown syndrome and inherited diseases during the first trimester, rather than waiting until the second trimester for an amniocentesis. CVS is done between the 10th and 12th weeks of pregnancy. It does not detect neural tube defects. A recent study showed that both tests had a small risk of miscarriage. That study of highly trained providers showed a risk of about 1 in 400.² Some studies have shown higher miscarriage risks, between 2 and 4 in 400.³ This greater risk may be more likely in medical centers with less experienced providers, especially for CVS. The CVS risk may be less when it is done through the abdomen than when it is done through the cervix.⁴

For more information, see the topic Birth Defects Testing.

Citations

1. American College of Obstetricians and Gynecologists (2004). ACOG issues position on first-trimester screening methods. Available online: http://www.acog.org/from_home/publications/press_releases/nr06-30-04.cfm.

2. Caughey AB, et al. (2006). Chorionic villus sampling compared with amniocentesis and the difference in the rate of pregnancy loss. Obstetrics and Gynecology, 108(3): 612–616.

3. Seeds JW (2004). Diagnostic mid trimester amniocentesis: How safe? American Journal of Obstetrics and Gynecology, 191: 608–616.

4. Alfirevic Z, et al. (2006). Amniocentesis and chorionic villus sampling for prenatal diagnosis. Cochrane Database of Systematic Reviews (1). Oxford: Update Software.