Most women first begin to suspect they're pregnant when they miss a period. Doctors can accurately diagnose pregnancy with a blood test within a few days after a missed period. Other early signs include breast enlargement or tenderness, a more frequent need to urinate, slight weight gain, morning sickness, fatigue, and a rounded abdomen. However, tests can now diagnose pregnancy earlier and more accurately than ever before. All such tests look for the pregnancy hormone, H-C-G. Urine tests are available at the doctor's office, or in over-the-counter versions you can use at home. Office tests can accurately detect pregnancy up to four or five days before your period is expected. Most home pregnancy tests work as early as the day your period is supposed to start. While their accuracy has improved, home tests can still give a false result in some cases, especially a false negative. So if you show other signs of pregnancy despite a negative reading, consult your doctor. Blood pregnancy tests, offered only by physicians, are the most expensive, but also the most accurate. They can establish pregnancy before a period is missed, and can also estimate how far along the pregnancy is. Blood tests are virtually 100 percent reliable. To confirm your pregnancy, the doctor will follow up with a pelvic exam, to see if the uterus has enlarged. For more information on diagnosing a pregnancy, see a health care provider.