Generally, getting your period is a pretty solid indication you aren’t pregnant, but generally is not always. Bleeding during pregnancy can be mistaken for a period while pregnant, and pregnancy bleeding, especially in the first cycle after conception, is more common than you might expect. Why?
Can you be pregnant and still have a period?
While you can have light bleeding around when your period is due and still be pregnant, you can’t have a true period while pregnant. If you are pregnant, ovulation won’t occur, and your uterine lining won’t be entirely shed along with an egg, so by definition, the bleeding isn’t a menstrual period.
What might cause bleeding around when your period is due in pregnancy?
Conception that occurs close to menstruation or low progesterone levels may cause what looks like a period.
Conception may not occur until mere days before your period is due if you have a short cycle or don’t ovulate mid-cycle. For example, let’s say you’re regularly maintaining a 26-day menstrual cycle. Chances are you’ll ovulate around cycle day 13. Even if fertilization occurred that day, it would still take six to twelve days for the fertilized egg to reach and implant in your uterine wall.
By this timeline, your body wouldn’t know to continue producing progesterone, the hormone that maintains the lining of the uterus during pregnancy, until somewhere between day 20 to 25 of your cycle. That could leave as little as one day between implantation and projected menstruation.
If those hormone levels are insufficient, such as in a situation of low progesterone from luteal phase defect, or they had already begun to fall, you might have what seems like a lighter than usual period or light spotting. You might even have what seems like an entirely normal period. In a situation like this, it’s possible not to have any indication you’re pregnant until you’re already around eight weeks pregnant.
This type of bleeding is often referred to as “breakthrough bleeding.” It’s the most common type of bleeding mistaken for a period while pregnant and is usually seen during the first month of pregnancy but may continue in the first trimester if hormone levels stay low. Basal body temping can be a great way to catch breakthrough bleeding, as after a rise in temperature confirms ovulation, prolonged high temps (more than 16 days) can be an early sign of pregnancy, period-like bleeding or not.
It’s important to note that any bleeding following the first bleed would not occur in a timely, predictable manner like a period. Bleeding in pregnancy will be sporadic with a varying flow. Multiple timely bleeds like a period, whether irregular or light for you or not, are very unlikely to be pregnancy bleeding.
As breakthrough bleeding can be indicative of low progesterone, it’s a good idea to let your healthcare provider know about it if you’ve confirmed you’re pregnant. In fact, any bleeding during pregnancy should be evaluated.
Implantation bleeding could be mistaken for a light period while pregnant.
Many women also mistake implantation bleeding for a light period while pregnant. Following the same example above, if you often have a light period, and had spotting on day 23, you might mistake that spotting as your period a day or two early.
The duration and flow of implantation bleeding vary from woman to woman, but it’s more commonly a light bleed, spotting, or pink-to-brown discharge 6 to 12 days after intercourse that lasts a day or less. It’s rarely heavy and typically won’t contain any clots. You can read a full article or try our quiz on telling the difference between implantation and your period here.
Sporadic bleeding during pregnancy is common in the first trimester.
Finally, numerous other issues can lead to light pregnancy bleeding in early pregnancy. Some examples include:
- Cervical changes (blood flow to the cervix increases in pregnancy)
- Bleeding from sex or heavy activity
- Placenta problems (can lead to heavier bleeding)
- Carrying multiples
- Progesterone dips (most common at week six)
- Ectopic pregnancy
- Threatened miscarriage
- Infection
In some cases, there is no clear reason for pregnancy bleeding. This page focuses more on bleeding that typically occurs very early, before a confirmed pregnancy. You can read more in-depth on other possible causes of early pregnancy bleeding seen more frequently after a confirmed pregnancy in the first, second, or third trimester here.
In short, vaginal bleeding doesn’t guarantee that you aren’t pregnant, but then it’s usually a pretty good indication. If in doubt, especially if you’re also experiencing early signs of pregnancy such as nausea, headaches, tender breasts, fatigue, bloating, food cravings/aversions, or mood swings, a home pregnancy test is the next step. Note that it’s best to wait to take a pregnancy test until at least four days after your period was due or 16 to 19 days after intercourse if you have irregular periods.
You may also find helpful:
How rare is it to be pregnant and have your period? What are the risk factors?
Missed period negative pregnancy test explanation
Early pregnancy symptoms quiz
Calculating your chances of pregnancy (also includes a quiz)