women s health issues
Detecting and Dating a Pregnancy
Laboratory pregnancy tests
Doctors test a sample of urine or sometimes blood from the woman to determine whether she is pregnant. These tests are more than 99% accurate. One of these tests, called an enzyme-linked immunosorbent assay (ELISA), can quickly and easily detect even a low level of human chorionic gonadotropin in urine. Some tests can detect the very low level that is present several days after fertilization (before a menstrual period is missed). Results may be available in about half an hour. During the first 60 days of a normal pregnancy with one fetus, the level of human chorionic gonadotropin in the blood approximately doubles about every 2 days. These levels can be measured during the pregnancy to determine whether the pregnancy is progressing normally. 