Home Pregnancy Test Accuracy: When Can You Get a Positive Result?

Question
Hi Dr. Kandeel,
I was just wondering what is the latest you have knowledge of a woman testing positive on a home pregnancy test, after previous negatives for the same pregnancy.  For example if someone has tested 3 times and gotten negatives but then tested again later on and got a positive and found out they were 9 weeks along is that normal?  Do some women just never get a positive on a home pregnancy test and why?

Answer
Dear Erica

It should not take more than 2 weeks after your missed period in order to have a positive test if you are pregnant. Home pregnancy test depends on the presence of a hormone called human chorionic gonadotrophins and it detects it maximum at 6 weeks calculated from the first day of your last menses or 2 weeks after your missed period.

To the best of my knowledge, it never lasted 9 weeks or more to test positive. It may test negative while you are pregnant if the test material itself is expired or not done the correct way.

Unfortunately I have no other explanation.

Good Luck