Blind panic. You looked at your calendar app and realized you were well past your period due date. A million and one scenarios flow into your head all at once. Am I pregnant? Do I have an STD? Am I unwell?

The truth is, there are a wide range of reasons why your period might be MIA after sex. And it doesn’t necessarily mean you’re pregnant.

Here’s what you need to know about missing a period and what to do about it.

Can having sex delay your period?

So, can having sex actually delay your period? No — having sex doesn’t delay your period or impact your cycle. There’s no scientific evidence that having sex can cause your period to be delayed or disappear.

But there are a range of different reasons why your period might be late.

Here are some common causes of a late or missed period:

  • Being pregnant
  • Changes in your menstrual cycle
  • Stress
  • Birth control
  • The start of menopause (perimenopause)
  • A medical condition
  • Polycystic ovary syndrome (PCOS)
  • Sudden weight loss
  • Heavy exercise
  • Breastfeeding

Let’s break down some common reasons why your period might be delayed or missing.

If you’re worried about a late or missing period, it’s always best to consult a healthcare professional. They’ll be able to give you personalized advice based on your unique symptoms and medical history.

Can having sex before your period delay it?

No, having sex before your period can’t delay your period, unless sex results in pregnancy. While some women report their period is delayed after having sex, there’s no physiologic basis for this.

6 reasons why your period might be delayed

A late period doesn’t always mean pregnancy — there are plenty of other factors that can throw off your cycle. From stress to shifting hormones, here are six common reasons your period might be delayed.

1. You’re pregnant

Okay, we had to start with this one. If you’ve had sex without using contraception, you might be pregnant. One of the earliest signs you’re pregnant is that you won’t have your period because pregnancy stops your periods until after you’ve given birth.

If you’re worried you might be pregnant, you can take a pregnancy test to check. A pregnancy test is most reliable if you take it on the first day of your missed period, but if you’re not sure when your period is, you can take a pregnancy test 21 days after having unprotected sex.

2. Your menstrual cycle has shifted

If your period is delayed after sex, it might be the result of natural shifts in your menstrual cycle. After all, our bodies don't exactly follow a precise calendar! Regular menstruation occurs every 21-35 days and normally lasts between 2-7 days. But 14-25% of women experience irregular menstrual cycles which could be why your period is delayed.

Irregular menstrual cycles are characterised by longer or shorter cycles, periods that are heavier or lighter than normal, and other irregularities like bleeding or spotting between periods or after sex.

If you’re experiencing irregular periods or periods that are often delayed, talk to a healthcare professional to discuss your symptoms.

3. Your body is under extreme stress

Severe stress can cause changes to your menstrual cycle, including delayed or missing periods. If your body is under a lot of stress, you might develop an irregular menstrual cycle and have a missed period.

As Dr. Caledonia Buckheit, OB/GYN, explains, “I like to tell patients, ‘if your body thinks you’re running from a bear, it won’t send the signals to ovulate and potentially get pregnant — and this will lead to menstrual cycle abnormalities!’”

A 2020 review on the menstrual cycles of young athletes found that young women who previously had regular menstrual cycles experienced changes in their menstrual cycle as a result of one or more factors, including:

  • Excessive exercise
  • Low weight
  • High stress

A 2024 study of 100 healthy, young students also found that women who reported menstrual irregularity reported significantly higher perceived stress than the women who had regular cycles.

If you’ve noticed changes to your menstrual cycle, including missing or delayed periods, it may be the result of high psychological stress or putting excessive stress on the body due to weight loss or extreme exercise.

4. You’re on birth control

Birth control can impact your menstrual cycle, including delayed or missing periods, or lighter bleeding during your period. If your period is delayed after sex and you’re on birth control, it’s less likely that you’re pregnant and more likely to be the result of hormonal contraception.

You might notice changes to your period when you start birth control, including:

  • Missed periods
  • Lighter periods
  • Spotting or bleeding between periods

If you’re worried about a delayed or missing period and you’re on birth control, talk to your healthcare provider. They’ll be able to assess your individual symptoms and advise on what path is right for you.

5. You’re starting menopause

If your period is delayed or missing, it might be a sign of perimenopause. During perimenopause, it’s common for ovulation to become less predictable, leading to irregular periods.

Perimenopause can start at different ages, but generally it begins 5-10 years before menopause. The average age for perimenopause is between 43-45 years old. Many women report experiencing perimenopause-related symptoms between the ages of 30-45 years old.

If you’re concerned about any perimenopause-related symptoms, talk to your healthcare provider.

6. You have an underlying medical condition

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If your period is delayed and you’re having irregular periods, it could be a sign of an underlying medical condition or disease.

Irregular menstrual cycles are associated with a range of medical conditions, including:

  • Type 2 diabetes
  • Metabolic syndrome
  • Coronary heart disease
  • Rheumatoid arthritis

If you’re experiencing irregular periods, consult a healthcare professional to rule out any medical conditions or diseases that might be causing irregular and missed periods.

Can having sex for the first time delay your period?

The short answer is no — simply having sex for the first time won’t make your period late. Your cycle is driven by hormones like estrogen and progesterone, and those don’t suddenly shift just because you’ve had sex.

The only way sex could change your period’s timing is if it led to pregnancy. If you had unprotected sex (or your contraception failed), a missed period can be one of the earliest signs of pregnancy. In that case, it’s a good idea to take a test if your period is late.

It’s also worth remembering that stress, anxiety, or even the anticipation around your first time can affect your cycle indirectly. Stress hormones like cortisol can interfere with ovulation, which may cause your period to arrive later than usual — but that’s not about the sex itself, it’s about what your body is experiencing in the moment.

Can having a lot of sex delay your period?

Nope. Having frequent sex — whether that’s daily, weekly, or somewhere in between — won’t change the timing of your period. Your menstrual cycle is controlled by your hormones and ovulation, not the number of times you have sex.

That said, sex can sometimes feel like it’s affecting your cycle because of the symptoms that follow. For example, vaginal soreness, light spotting, or changes in discharge after frequent sex can be mistaken for early period signs. But these aren’t actually delays — just temporary changes linked to friction, hormonal shifts during your cycle, or even minor cervical irritation.

If your period is late and you’ve been having a lot of sex, pregnancy is still the only sex-related reason. Otherwise, your cycle is likely responding to the usual suspects — stress, illness, travel, or hormonal fluctuations.

Can having sex delay your period even on birth control?

Having sex can’t delay your period, but birth control can sometimes cause irregular or missing periods. You may find that your periods become less frequent, lighter, or stop completely if you’re using birth control.

If you’re concerned about any changes to your period while you’re on birth control, speak to your healthcare provider to discuss your symptoms.

Sex doesn’t put your period on pause

A late or missing period can cause instant panic, especially if you’ve recently had sex. But if your period is MIA, there are several reasons why your period might be delayed and why you might be experiencing irregular cycles or changes to your period. If you’re concerned about a late or missing period, talk to a healthcare professional to discuss your individual symptoms and figure out what’s going on.

Whatever’s happening, there’s a path you can take to understand your symptoms and make sure you have the right treatment plan or lifestyle changes you need.