Finding out you’re pregnant can be a life-altering event. Many couples want to know if they’re pregnant as soon as possible, and rely on over-the-counter pregnancy tests to confirm their suspicions. Others prefer the reassurance of a physician, and would like to know that their pregnancy is proceeding well. This article provides information about pregnancy tests and determining when a pregnancy seems healthy.

Conception occurs when an egg is fertilized by a sperm, usually about two weeks after the first day your menstrual cycle begins. This fertilization occurs within one of your fallopian tubes. It takes several days for the fertilized egg to travel from your fallopian tube to the uterus and implant within your uterine wall, and several more days until hCG (human chorionic gonadotropin) – called “the pregnancy hormone” – is produced in detectable levels. HCG levels rise as the pregnancy develops, doubling approximately every two to three days in the first weeks of pregnancy.

Pregnancy tests detect hCG. A qualitative blood or urine test only indicates if this pregnancy hormone is detectable or not. A “positive” result means that hCG is present, indicating you are pregnant. With a “negative” test result, either you’re pregnant and the level of hCG is still too low to be detected, the test was performed incorrectly, or you’re not pregnant and there is no hCG present at all. If you still feel pregnant after a “negative” test result, it’s worth repeating the test in a few days.

Blood tests will detect hCG approximately as early as eight or nine days after conception. Urine tests require a larger amount of hCG to show positive results, and first become positive 10 – 12 days after conception. Therefore, a blood test can detect a pregnancy sooner than a urine test. And, a urine test will usually be positive by the time you would expect to have your next menstrual cycle.

While a positive pregnancy test can confirm that you’re pregnant, one test alone may not indicate whether your pregnancy is healthy. A “viable” pregnancy is one that is continuing to grow. Once a pregnancy stops growing, it no longer produces new hCG. However, it will take days or weeks for the existing hCG to be cleared from your body. Therefore, a pregnancy test may remain “positive” for weeks after an unhealthy pregnancy has stopped growing.

There are ways to ascertain if an early pregnancy is still viable. These tests are particularly useful if concerns arise during your early pregnancy such as bleeding, cramping or a loss of pregnancy symptoms.

1) Quantitative blood tests. A quantitative blood test measures the quantity of hCG in your blood. There is a range of normal values, which vary between women. Rather than comparing your hCG level to a chart, most obstetricians wish to measure the change in your hCG level over time. A healthy pregnancy shows a doubling of hCG every two to three days. After the first 60 days of pregnancy, the levels start to decline. In early pregnancy, your health care provider may request serial hCG blood tests every few days to see if levels are rising appropriately.

2) Ultrasound exam Early pregnancies grow in predictable ways that can be visualized using ultrasound. First, a small sac of fluid (called a gestational sac) is visible within the uterine cavity. Later, a small yolk sac can be seen (which provides nutrients to the young embryo) at five weeks. Then, a small embryo is seen (called a fetal pole). And finally, a healthy embryo will show a beating heart by about seven weeks. Comparing your ultrasound findings to what is expected based on your last menstrual period can help your obstetrician determine if your pregnancy is healthy.

If you do discover you’re pregnant, write down the date of your last menstrual period and make an appointment to see your health care provider.