The simple answer is that it is possible to get pregnant from having sex on a period bleeding. Your menstrual period bleeding and menstruation is falsely believed to be a "safe" period of time in your monthly cycle when you can have unprotected intercourse and not get pregnant. This is a myth, and nothing is further from the truth.

You can still get pregnant on your menstrual period bleeding if you have unprotected sex. Sperm survive up to five days, and iof ovulation happens within 5 days after having had sex, the you could get pregnant. Some women can ovulate within 5 days of their menstrual period bleeding and get pregnant from having intercourse during the menstrual bleeding. And if you make love within 5 days of ovulation then it is possible to get pregnant.

Sperm have the amazing ability to live for up to 5 days inside of the female body, which is why you can get pregnant on your period. This amazing survival time means that you can actually get pregnant — that the egg gets fertilized — on a different day than when you had sexual intercourse. That sounds strange, but it is true!

Can you get your menstrual period bleeding once you are pregnant?

It is possible but highly unlikely to have a regular menstrual period bleeding once you are pregnant. When you are pregnant, you may have some spotting or bleeding, but it's rarely a regular menstrual period bleeding. A regular menstrual period bleeding is moderate to heavy bleeding, lasting 3-5 days. Up to 30% of pregnant women experience some small mount of spotting or vaginal bleeding early in pregnancy, and most go on to have a normal pregnancy.

Some even report intermittent bleeding that seems like a regular period to them. But vaginal bleeding during pregnancy is not the same thing as menstruation. 

What's the difference?

Menstruation only happens when you're not pregnant in repopsnse to ovulation and the uterine lining shedding when the egg has not implanted: Each month, your uterus grows a thick blood-rich lining in preparation for an egg to embed there. If you don't get pregnant that month, you shed this tissue and blood – that's your menstrual period.

But once an egg embeds in the uterine lining, hormones tell the blood-rich tissue to stay intact to support the fetus . 

Then why do some women bleed during pregnancy?

Bleeding occurs during pregnancy for various reasons, some serious and some not.

Some women have light bleeding or spotting very early in pregnancy – around the time their period is due – and they may mistake that for a period. This so-called "implantation bleeding" may be caused by the fertilized egg burrowing into the blood-rich lining of the uterus. It's generally a lot lighter than a typical period and lasts just a day or two.

You may have spotting after a Pap smear, vaginal exam, or sex. This is because there's more blood going to your cervix during pregnancy.

Bleeding can also be a sign of something seriously wrong, such as a miscarriage or an ectopic pregnancy which can be life-threatening. 

If you notice bleeding in pregnancy, call your doctor right away, even if the bleeding has stopped. Many women who bleed a little during pregnancy deliver without complications, but you may need an evaluation to rule out a serious problem.

If you're actively bleeding or have severe pain of any kind and can't immediately reach your practitioner, head straight to the emergency room.

If you have sexual intercourse while you are on your period, and the sperm stays alive for 4-5  days inside of you, and then you ovulate while the sperm is still there, you can get pregnant on your period.

Some women can not actually get pregnant on their period, because ovulation happens more than 5 days after their period ends.  But others, due to the timing of their periods and earlier ovulation, can get pregnant on their period.

Women with shorter menstrual cycles ovulate earlier. For example, those with menstrual cycles of 21 days will ovulate usually on cycle day 7, which is just a few days after your menstrual period ends.

The fact is that you can get pregnant on your period. This is why it is important to continue to use your birth control method all the time, even when having intercourse while having your period.

If you are on the birth control pill or a vaginal hormone ring that is removed during menstruation, you are still covered while on your menstrual period. The hormones do not leave your body in that period of time, as long as you use your method as directed.

And birth control pills cannot protect you from sexually transmitted infections or HIV, so using condoms at all times is a smart idea. Even though you are unlikely to get pregnant on your period, you still have the same risk of contracting a sexually transmitted infection, including HIV.

The general rule is that if you had a regular period then you are not pregnant. Being pregnant even though you just had your period is a rare exception, not the rule. You could be pregnant, but it's not likely that you are pregnant, especially if you have a negative pregnancy test.

A normal menstrual period comes on time, is the usual amount of flow, and lasts the regular 3-5 days. When you are not pregnant then you get a menstrual bleeding, your period. Your regular menstrual period usually comes about 14 days after ovulation because you are not pregnant.

Being pregnant even though you just had your regular period is a rare exception, not the rule. You could be pregnant, but it's not likely that you are pregnant. 

No matter how much you speculate and ask yourself if this was a real period or not, whether it was shorter than usual or came at a different time than usual and whether you could be pregnant or no. The answer is the same:

If you have a negative pregnancy test then you are not pregnant.

Women with regular menstrual periods are unlikely to be pregnant, especially if home pregnancy tests are repeatedly negative. Some pregnant women report that they have vaginal bleeding early on in pregnancy. But this bleeding is usually not like a regular period, it's usually much lighter and irregular, more like spotting. If you are in doubt, do a pregnancy test. It should be positive if you are pregnant.