Although a missed period or loss of menstruation is not a reliable sign of pregnancy, it is the most obvious early sign of pregnancy especially if it is accompanied by nausea and vomiting (morning sickness), breast tenderness, fatigue, and urinary frequency.
The early signs of pregnancy – missed period and others as mentioned above, represent presumptive changes that are not considered reliable indicators of pregnancy since any one of them can be a sign of conditions other than pregnancy. For example, loss of menstruation can be caused by endocrine dysfunction, early menopause, malnutrition, diabetes mellitus, anemia, long-distance running, or stress.
Furthermore, nausea and vomiting can be caused by food poisoning, gastrointestinal disorders, eating disorders, or acute infection. Breast tenderness may stem from premenstrual changes, chronic cystic mastitis or the use of oral contraceptives, while fatigue could be a result of stress, anemia, or viral infections.
Urinary frequency can have a plethora of different causes other than pregnancy, most notably infection, cystocele, structural disorders, pelvic tumors, or even emotional tension. Thus, although a combination of early signs can suggest pregnancy, they are not reliable in confirming this condition.
This is why the use home pregnancy tests (based on the detection of urinary human chorionic gonadotropin) is recommended as an initial step when suspicions exists. With modern, clinically sensitive urinary pregnancy tests, pregnancy may be detected up to four days before the expected period.
Blood tests often done in the hospital settings is more effective. They can pick up hCG earlier in a pregnancy than urine tests can. Blood tests can tell if you are pregnant about six to eight days after you ovulate.
All pregnancy tests work by detecting a special hormone in the urine or blood that is only there when a woman is pregnant. It is called human chorionic gonadotropin, or hCG. hCG is made when a fertilized egg implants in the uterus and it rapidly builds up in your body with each passing day you are pregnant.
If you feel pregnant because you missed your period, coupled with other pregnancy symptoms, testing your urine and or blood is more affirmative than just relying on the symptoms alone as many other things can mimic pregnancy symptoms.
Source: newsmedical, women’shealth.gov