If results are positive, the woman should contact her doctor, who may do another pregnancy test to confirm the results.
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.
In other words, a woman who is 4 weeks pregnant is carrying a 2-week-old embryo.
If a woman’s periods are irregular, the actual difference may be more or less than 2 weeks.
Some vaccines, such as the measles, mumps, rubella (MMR) vaccine, should be given a month or more before pregnancy.