usually does not cause any problem on growing embryo before confirmation of pregnancy
or organogenesis of fetus (4-5 weeks onwards).
You can take the medicine to postpone period for 1-2 days only as you are TTC in this month. It should be taken 3 days prior to due date. You will get period within 3-5 days of stopping the pill in absence of conception.
If your period is delayed more than 7 days, you would undergo one home pregnancy test to check pregnancy status. Blood test
is more reliable. Study proves that norethisterone
(regestrone) should not be taken after 5 weeks of pregnancy.
Hope, it helps for you. For more details, you can visit my profile for direct query. Be well.