Though you may feel relieved believing that you can only get pregnant during and around ovulation, it is not always the case. It is still possible to get pregnant after unprotected sex, specifically at the beginning of your period. There is a widespread belief that you can’t get pregnant during menstruation. However, it is a myth and is far from being evidence-based information; in this article, we will tell you why.
It relates partially to the variability in different people’s cycles. Though the typical menstrual cycle lasts 25 to 30 days, this can vary from person to person. A shorter menstrual cycle will increase your chances of pregnancy if you engage in unprotected sex. Additionally, some people have irregular periods, making menstrual phases difficult to track and, thus, complicating menstrual period and pregnancy calculation tracking. It can also be challenging to know exactly when you are ovulating, unless you are consistently taking and tracking your basal body temperature (1). To best understand your fertility windows, it is important to know your menstrual cycle and its phases.
Understanding the menstrual cycle
To track your fertility and chances of pregnancy, it is important to first understand your menstrual cycle and how this impacts your chances of conceiving. A typical cycle lasts between 28 to 29 days, although this can vary from person to person (2). During your cycle, you rotate through four separate phases, known as your menstrual, follicular, ovulation, and luteal phases. Each of these stages are characterized by hormone fluctuations, manifesting as physical and emotional changes in your body. These hormone fluctuations influence your ability to get pregnant in that phase.
The menstrual phase is when you get your period. Your period is the result of your uterine lining shedding and expelling from your vagina. The blood you see with your period also contains mucus and cells from your uterine lining. Typically, the menstrual phase, or menses, lasts between three to seven days (2).
The follicular phase begins on the first day of your period and continues for 13 to 14 days thereafter until ovulation. During this time, your pituitary gland produces follicle-stimulating hormone (FSH), which activates follicle production in the ovaries. At this time, your body prepares for pregnancy by thickening the uterine wall (2).
Ovulation occurs once monthly, roughly two weeks prior to your next period. Ovulation happens when your ovaries release a mature egg, which will later travel down the uterine tubes to your uterus. This phase lasts for about 16 to 32 hours and is considered your most fertile window (2). We will discuss fertility in the context of ovulation later in this article.
The final stage of your cycle is the luteal phase. This occurs after ovulation and is when your ovaries produce progesterone and estrogen. These hormones further thicken the uterine lining in order to sustain a pregnancy.
During the luteal phase, if a fertilized egg attaches to the uterine lining, progesterone production will continue with pregnancy. If it does not implant in the uterine lining, the lining will shed, and your next period will start (2).
Fertility and ovulation
Your chances of getting pregnant are highest five days prior to and on the day of ovulation. This is because during ovulation the egg is released and moves down the uterine tubes. It stays there for 12 to 24 hours; during this stage, the egg can be fertilized. It is also important to note that sperm is viable in the reproductive tract up to five days after sexual intercourse, so its presence in the uterine tubes can cause conception. That is why your odds of pregnancy are highest at ovulation and the preceding five days (3).
How do I know if I am ovulating?
It can be difficult to determine when you are ovulating as every person’s cycle is different. If you have a regular period with a 28-day menstrual cycle, you can estimate your ovulation by tracking your periods in a menstrual calendar, for example, with an app. You can also look out for other signs of ovulation, which include your body temperature and vaginal secretions. This is known as the Fertility Awareness Method (FAM).
- Basal body temperature. The temperature of your body elevates subtly when you are ovulating. You can track your basal body temperature with a specific thermometer that is sensitive to these changes. With this thermometer, you take your temperature first thing in the morning and track your measurements by registering the temperature fluctuations over a specific body basal chart. Your most fertile window is two to three days prior to an increased temperature.
- Vaginal secretions. Your vaginal secretions (discharge) change throughout your cycle depending on what phase you are in. Before ovulation, your discharge will likely be wet, clear, and stretchy, known as the egg white discharge. Immediately after ovulation, it may be cloudy and thick (3).
Safe practices and pregnancy prevention
Though tracking your cycle and phases can be both informative and helpful in preventing pregnancy, it is not a foolproof method. You can still get pregnant while on your period. To best prevent pregnancy, it is important to implement a birth control method or multiple birth control methods. These can include condoms, hormonal birth control, or an intrauterine device (IUD).
It is also important to note that having sex on your period can increase your risk of contracting sexually transmitted infections (STIs). For example, if an individual with hepatitis or HIV has sex during their period, their partner is at increased risk of contracting these viruses because of blood contact. So, if you choose to have sex during your period, use condoms to prevent transmission of STIs (4).
- “Can you get pregnant if you have sex during your period?” Planned Parenthood, 2013, www.plannedparenthood.org/blog/can-you-get-pregnant-if-you-have-sex-during-your-period#:~:text=Yes%20%E2%80%94%20it’s%20possible%20to%20get,when%20an%20egg%20is%20released. Accessed August 2023.
- “Menstrual Cycle.” Better Health Channel, www.betterhealth.vic.gov.au/health/conditionsandtreatments/menstrual-cycle. Accessed August 2023.
- “Ovulation signs: When is conception most likely?” Mayo Clinic, www.mayoclinic.org/healthy-lifestyle/getting-pregnant/expert-answers/ovulation-signs/faq-20058000. Accessed August 2023.
- Chisholm, A. “Period Sex: Can You Have Sex on Your Period?” Verywell Health, 2023, www.verywellhealth.com/sex-during-your-period-2721991#:~:text=Summary,sexually%20transmitted%20infection%2C%20is%20higher. Accessed August 2023.