A pregnancy test attempts to determine whether or not a woman is pregnant. Modern pregnancy tests look for chemical markers associated with pregnancy. These markers are found in urine and blood, and pregnancy tests require sampling one of these substances. The first of these markers to be discovered, human chorionic gonadotropin (hCG), was discovered in 1930 to be produced by the trophoblast cells of the fertilised ovum (blastocyst). While hCG is a reliable marker of pregnancy, it cannot be detected until after implantation: this results in false negatives if the test is performed during the very early stages of pregnancy. Obstetric ultrasonography may also be used to detect pregnancy. Obstetric ultrasonography was first practised in the 1960s; the first home test kit for hCG was released in the mid-1970s.
One of the most common drawbacks of being pregnant is having to deal with morning sickness and nausea. Just the sight and smell of some of the most common foods will make you want to run to the bathroom and hurl. Luckily morning sickness and nausea usually only last for the first three to four months of pregnancy.
Pregnancy is the carrying of one or more offspring, known as a fetus or embryo, inside the womb of a female. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets. Childbirth usually occurs about 38 weeks after conception; i.e., approximately 40 weeks from the last normal menstrual period (LNMP). The World Health Organization defines normal term for delivery as between 37 weeks and 42 weeks.