Medical Q&As

Pregnancy test - positive before missed period?

Is it necessary to wait for a missed period before conducting a pregnancy test?

It is not necessary to wait for a missed period before having a pregnancy test performed. Most pregnancy test kits can detect pregnancy earlier than this. The tests in common usage detect HCG (human chorionic gonadotrophin) in the urine. HCG is produced within the trophoblast, which is a precursor of the placenta or afterbirth. The trophoblast starts secreting HCG as early as 5 days after conception but it is not detectable until implantation takes place which occurs 8 or 9 days after fertilisation. At this point the level of HCG rises dramatically and doubles in amount every 48 hours. HCG is a hormone and its function is to stimulate the corpus luteum to produce oestradiol and progesterone in the first trimester of pregnancy. The corpus luteum is a hormone-secreting structure that grows on the surface of the ovary after ovulation takes place. HCG levels continue to increase during the first trimester and eventually reach a peak level 60 to 80 days after implantation. The hormone is produced irrespective of the site of implantation and is present in cases of ectopic pregnancy.