Modern Tests
The test for pregnancy which can give the quickest result after fertilisation is a rosette inhibition assay for early pregnancy factor (EPF). EPF can be detected in blood within 48 hours of fertilization. However, testing for EPF is expensive and time-consuming.
Most chemical tests for pregnancy look for the presence of the beta subunit of hCG or human chorionic gonadotropin in the blood or urine. hCG can be detected in urine or blood after implantation, which occurs six to twelve days after fertilization. Quantitative blood (serum beta) tests can detect hCG levels as low as 1 mIU/mL, while urine test strips have published detection thresholds of 20 mIU/mL to 100 mIU/mL, depending on the brand. Qualitative blood tests generally have a threshold of 25 mIU/mL, and so are less sensitive than some available home pregnancy tests. Most home pregnancy tests are based on lateral-flow technology.
With obstetric ultrasonography the gestational sac sometimes can be visualized as early as four and a half weeks of gestation (approximately two and a half weeks after ovulation) and the yolk sac at about five weeks' gestation. The embryo can be observed and measured by about five and a half weeks. The heartbeat may be seen as early as six weeks, and is usually visible by seven weeks' gestation.
Read more about this topic: Pregnancy Test
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