When you're wondering if you're pregnant, every extra day you have to wait to find out seems like an eternity. Fortunately, it's possible to find out whether you're pregnant very early -- often around the time of your first missed period. Blood tests and fetal ultrasound are the most accurate pregnancy tests but require your doctor's assistance. Although less sensitive at detecting early pregnancy, urine pregnancy tests are available over the counter, and testing can be done at home.
Home Pregnancy Tests
Over-the-counter home pregnancy tests, or HPTs, are easy to use and noninvasive. HPTs measure the amount of human chorionic gonadotropin, or hCG, in the urine. The hCG hormone is produced by the growing placenta, the organ within the womb that provides nutrition and oxygen to the baby. The hCG level rises rapidly during the initial weeks and months of pregnancy. Many HPTs claim to detect very low levels of hCG, around the time of your first missed period. Some HPTs also estimate how many weeks pregnant you are, but the results may not be accurate if your menstrual cycle length varies or if you are carrying more than 1 baby.
Choosing and Using a Home Pregnancy Test
Many brands of HPTs are available, and some are more sensitive than others. In general, the lower the hCG level a test detects, the earlier it can give you a positive test result. Check your first morning urine, since it typically contains the highest concentration of hCG. Follow the directions exactly and read the result only during the time frame listed. If you wait too long, you may get a false result. Even if you take the test correctly, the results may not always be accurate. If the HPT result is negative and you still haven’t gotten your period 2 days later, take the test again.
Blood Tests for Pregnancy
Blood pregnancy tests also measure the amount of hCG. The hormone appears in small amounts in the blood and urine as early as 8 days after conceiving. The advantage of blood pregnancy tests is they can measure precise amounts of hCG -- called quantitative measurement -- and can detect the presence of hCG earlier in pregnancy than urine tests.
Ultrasound to Determine Pregnancy
Pelvic or abdominal ultrasound can show that you're pregnant from around 5 weeks of pregnancy. They show the gestational sac, a fluid-filled structure surrounding the growing embryo. An early fetal ultrasound provides the most accurate method of determining your due date. Transvaginal ultrasound, which involves use of an ultrasound probe that fits into the vagina, provides a better look into the uterus than abdominal ultrasound, particularly if you're overweight.
When to Seek Medical Care
Schedule an appointment to see your health care provider if you have a positive pregnancy test. Early prenatal care is important for the health of both you and your baby. If you have a negative test but think you might be pregnant, call your doctor. Seek immediate medical care if you’re pregnant and experience severe abdominal pain, cramping or vaginal bleeding.
- Clinical Chemistry and Laboratory Medicine: The hCG Assay or Pregnancy Test
- DC Dutta's Textbook of Obstetrics; Hiralal Konar
- American Journal of Clinical Pathology: Should the Qualitative Serum Pregnancy Test Be Considered Obsolete?
- Perinatology.com: Beta hCG Doubling Time Calculator
- Foye's Principles of Medicinal Chemistry; Thomas L. Lemke, et al.
- The Immunoassay Handbook, 3rd Edition; David Wild
- Clearblue: Clearblue Advanced Pregnancy Test With Weeks Estimator
- Sonoguide.com: Ultrasound in Early Pregnancy