Birth control pills and pregnancy

[Tassha1223]

Dear Scarleteen,
I guess you can say I'm a worrier. I always worry over the slightest thing.
And I thought maybe if I get an answer to my questions I'll stop worrying as much.
I've been on yaz for over 2 years now but there is one thing I don't understand.
If you were to have breakthrough ovulation on birth control pills it would be like a normal cycle and if you happened to get pregnant at that time you wouldn't have a bleed and if you wouldn't become pregnant you'd bleed like you normally do on the pills but with the ovum, right? So does that mean that a normal 5 day long withdrawal bleed is a sign that you are not pregnant?
I have heard of people who had such bleeding and still were pregnant. Could you please explain why they would still have a normal bleed and be pregnant at the same time?
My other question is being on yaz i have 24/4 pills and the bleed usually comes on the placebo days, but somehow this time it came on the first active pill after my last placebo. Is that a concern?

And my last question is how many days do you need to wait for the most accurate pregnancy test result? Is 3 weeks really reliable or is it better to wait longer?

Also thank you for taking the time to read my post and answer these questions! I really appreciate it

[Sam W]

Hi Tassha,

To start out with, it might help to know that preventing ovulation is only one of three ways that the pill works to protect you from pregnancy. It prevents ovulation but it also makes it so that your vaginal secretions become and remain thicker (to make it tougher for sperm to get to an egg in the case ovulation did occur), and so that that endometrial lining doesn't build up as much (in the case that the other two modes go awry, that would make it really tough for a fertilized egg to implant). That's part of why the pill is so effective when taken correctly; it has multiple ways of preventing pregnancy.

As for your questions about bleeding, if someone gets their withdrawal bleed (or their period) they can assume they're not pregnant. The reason you'll sometimes hear stories about people getting their period while pregnant is that there can be implantation bleeding (when the fertilized egg implants into the lining of the uterus) or decidual bleeding (when the uterus sheds a bit of lining during pregnancy), but those aren't the same as periods. With bleeding slightly later than normal while on the pill, that's something that can happen every now and then. Your period (or withdrawal bleed) won't always arrive at the same time every month, even when you're on the pill.

With pregnancy tests, when you can test varies depending on what test you buy. You can read more about that here: Peeing on a Stick: All About Pregnancy Tests

[Tassha1223]

Dear Sam,

Thank you for responding. My last question is, if someone was pregnant and on the pill and did have implantation bleeding or decidual bleeding would it be the same amount and colour as a normal withdrawal bleed? Can implantation and decimal bleeding have heavy to moderate flow and last more than 3 days?
Is there a way to tell the difference?

[Sam W]

You're welcome! Generally speaking, implantation bleeding is not going to look or feel like a period (and probably won't come at the time you're expecting a period). Some people can mistake decidual bleeding for a period because of how it looks, but decidual bleeding isn't that common.