Whether you’re trying to get pregnant — or actively trying to avoid it — timing is everything. And, when it comes to when you can get pregnant, the answer might not be as cut-and-dry as you would like. The truth is, some people can conceive when they’re on their period, but it’s a very low percentage for several reasons, which we’ll dive into.
In a nutshell, while most people only have about a six-day window of opportunity around ovulation to get pregnant, there are certainly some exceptions to the rule. Additionally, most ovulate in the “middle” of their cycle, around day 14, but there are outliers to that rule since all bodies are different.
Can you get pregnant on your period?
The short answer is: yes, but it's unlikely. If you have intercourse during your period and ovulate within five days, the sperm can still be viable when the egg is released, potentially resulting in pregnancy. The odds are extremely low if it’s your first or second day of bleeding, but the likelihood increases with each successive day. So, if you have sex toward the end of your period and ovulate early, there is a chance.
Can you get pregnant when you're not ovulating?
Your highest likelihood for a successful pregnancy occurs during your ovulation window. However, it is possible to get pregnant at other times throughout the month as well.
The first reason for a potential pregnancy “outside” of your ovulation window would be because sperm can live inside the female reproductive tract for up to five days. This means that your “fertile window” can start up to five days before ovulation. That’s why the American Society for Reproductive Medicine (ASRM) defines the fertile window as the six days ending on ovulation day, based in part on a 1995 study in the New England Journal of Medicine.
Additionally, ovulation can be difficult to predict and may vary from month to month, even if you’re tracking your cycle. Some women have irregular periods, making it difficult to know when they’re ovulating. While there are many ovulation predictor kits and apps available, these are not completely accurate and should not be solely relied on to plan (or avoid) conception.
How ovulation and the menstrual cycle work
To understand when you can or cannot get pregnant, you first need to understand the female menstrual cycle. The menstrual cycle is the process by which a woman's body prepares for a potential pregnancy each month. The cycle is often described in four phases: the menstrual phase, the follicular phase, ovulation, and the luteal phase, though technically your period kicks off the follicular phase.
Menstrual phase
The menstrual phase, also known as your period, typically lasts between 3 and 7 days and is the time when the uterus sheds its lining, along with blood and other tissue. It may also be accompanied by cramping, breast tenderness, headaches, and mood swings, among other symptoms. For many, it's the uncomfortable time of the month when we'd rather not be having intercourse anyway. And for those trying to avoid pregnancy, the odds of becoming pregnant during this phase of your cycle are very low. The first day of your period is commonly referred to as day 1 of your cycle.
Follicular phase
The follicular phase starts with the menstrual phase and lasts for about 14 days, on average. During this time, the body releases hormones that stimulate the growth of one or more follicles in the ovaries. These follicles contain eggs, and one will typically become dominant, reaching maturity, and releasing an egg during ovulation.
Ovulation
Ovulation typically occurs around day 14 of the menstrual cycle but can vary greatly. This part is key because each of us is different and our bodies are unique. Ovulation may happen earlier or later for you, and it’s worthwhile to keep track of your cycle either with a tracking app or ovulation tests so that you know when to expect that all-important egg release.
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Luteal phase
The luteal phase begins after ovulation and lasts for another 14 days, on average. During this time, the body releases hormones that help prepare the uterus for pregnancy.
If sperm fertilizes the egg in the fallopian tube — which has to happen within about 12 to 24 hours of ovulation, while the egg is still viable — and the embryo then travels to the uterus and successfully implants into the lining, you’ll be pregnant. If the egg is not fertilized, the uterus will shed its lining during the next menstrual phase, and the cycle will begin again.
Cycle length
While many people have a standard 28-day cycle, typical adult cycles range from about 21 to 35 days. Cycles that are consistently shorter or longer than that are worth bringing up with your doctor. So predicting ovulation can be tricky if you don’t understand your unique cycle. Additionally, some people ovulate earlier in their cycle than others, so knowing your body and when it’s entering its “fertile window” is key to knowing when you have the potential to become pregnant.
Also, if for some reason you miss your period, it doesn’t necessarily mean that you’re pregnant. There may be other factors at play.
Other factors that affect your chances of getting pregnant
In addition to our fluctuating cycles, other factors can impact a woman’s potential to get pregnant. You’ll especially want to be aware of the things that you can avoid and that you’re in control of if your goal is to grow your family.
Some factors that can affect fertility include:
Age: Fertility declines gradually but significantly starting around age 32, and more rapidly after 37, according to a joint committee opinion from ACOG and ASRM. Age affects men’s fertility, too, though much less than women’s.
Lifestyle: Certain behaviors such as smoking, drinking, and being overweight or underweight can affect a person's fertility. This also goes for men and women.
Health conditions: Certain health conditions, such as polycystic ovary syndrome (PCOS) and thyroid disorders, can make it more difficult for a woman to get pregnant.
Medications: Some medications can affect fertility, so it’s worth reviewing anything you take with your doctor if you’re trying to conceive.
The bottom line
While your chances of getting pregnant are significantly better while you’re ovulating, it is possible to get pregnant if you have sex during your period. So if your goal is to conceive, it helps to have a healthy lifestyle and track your cycle to understand when you have the best chance at conceiving. If you want to avoid pregnancy, monitoring your cycle is still key to understanding your body and using the right form of birth control for you and your partner.
