They all work on the same principle — determine the presence in the urine of women specific "pregnancy hormone" human chorionic gonadotropin. Pregnancy test it is better to do this morning — then the result will be more accurate. Another method is measurement of basal temperature on the first day of menstruation. To measure the temperature necessary in the morning the usual medical thermometer is basal if the temperature is raised (more than 37), the probability of pregnancy is high. This method cannot be considered as accurate as possible.
A more reliable method of determining pregnancy are laboratory studies — it is necessary to take blood from a vein, and after a few hours, the result is ready. This way you can determine not only the presence or absence, but the exact period of pregnancy and in the early period — within 10 days after conception (i.e. even before the delay cycle).
Another pretty accurate and common method, giving the opportunity to learn about the early pregnancy — ultrasound (ultrasound). It can be done only after the fact, from the moment of conception, it took more than three weeks otherwise the result will be inaccurate. Today was carried out as transabdominal and transvaginal ultrasound in the first case the sensor is placed on the woman's stomach, the second directly into the vagina, which allows to obtain the most accurate result. If all the studies have confirmed the presence of pregnancy — visit the gynecologist.