Scarleteen

Hi Scarleteen, this specific question was born out of a thought train I had driving on the interstate that went from “wow biology and development is so cool” to “fetal development in mammals, especially humans, is so unique” to “wait, how would birth control affect the symptoms of pregnancy”.

I know that generally it’s impossible to have a period while pregnant, it’s counterintuitive biologically. You can have lighter bleeds from implantation or infection or trauma, and heavier ones from a miscarriage. But not what would be a typical run of the mill period.

I also know that, technically, a period on birth control, specifically the pill, isn’t a true period. It gets close because it’s caused by a cycle of hormones, but not a natural one. When you take the placebo pills in a pack, you bleed because of the drop of hormones.

This led to me wondering if it was possible to continue to have one of these periods if you got pregnant while on birth control. Assuming you didn’t know and continued to take pills as normal up until what would be the period week, would the drop in hormones still make you bleed? Or would pregnancy hormones have already kicked in and not let that happen?

I haven’t been able to find any answers on this other than one article saying “well maybe” and one forum that had a “this happened to someone I knew” situation, so I’m inclined to say probably not, but I know many of the people on Scarleteen are more experienced with fertility and human development than I am.

Please answer whenever you can! These things fascinate me to know and think about!

Hi Digdawg!

You are correct that people who experience a period while taking hormonal birth control, particularly oral contraceptives and the vaginal ring, have a different period than those without birth control. Different from menstrual periods, periods with birth control are called withdrawal bleeding and are caused by the drop in hormone levels (like when taking the placebo pill of oral contraceptives). The uterine lining is still shed, but ovulation in the cycle stops. So, I would still call this a natural period, the hormone levels are just “manipulated” by birth control.

When a person becomes pregnant and remains so, they won’t experience menstrual periods or withdrawal periods (but they can experience spotting). During a person’s cycle, the lining of the uterus thickens to prepare for pregnancy. So, if a person is pregnant, that uterus lining must be sustained to remain pregnant. Therefore, they wouldn’t have a period, withdrawal or menstrual. That means that withdrawal bleeding is actually a good indicator that a person is not pregnant!

Thanks for answering!

I had figured that was the case, but it’s still so cool to know! I think I’m always in awe at how unique the human (and similar primates) fertility cycles are compared to other mammals!