If you're searching for “when can you not get pregnant,” you're likely either trying to avoid pregnancy or understand when the chance is lowest. The most important thing to know is that pregnancy can typically only occur within a specific "fertile window" around ovulation, but cycles can vary from person to person and from month to month. Therefore, it's rarely possible to say there are completely "safe days" without using contraception. Below is a practical guide to times when pregnancy is usually less likely, and when it is practically impossible.

The term “safe period” is often used to describe days when the probability of pregnancy is low. In practice, it depends on when you ovulate and how regular your cycle is.

As a birth control method, "safe periods" are generally considered unsafe compared to, for example, hormonal contraception or barrier methods. Read more about safe periods at Sundhed.dk (Patient Handbook): https://www.sundhed.dk.

The chance is typically lowest outside the fertile window. For many, the highest probability is in the days leading up to and around ovulation, while the probability often decreases after ovulation, when it is longer until the next menstruation.

• Days well after ovulation (luteal phase) are often associated with lower probability.
• Days early in the cycle can also be lower risk for some, but not for all, especially if the cycle is short or ovulation occurs early.

If you want to time or avoid pregnancy based on your cycle, it can be more accurate to combine methods like ovulation tests (LH tests) and cycle data rather than just the calendar.

For many, the probability is low during menstruation itself, but it is not necessarily zero. This is mainly because sperm can survive for several days, and some women have early ovulation or short cycles.

• With a short cycle, where ovulation can occur relatively early.
• If the bleeding is not menstruation, but, for example, spotting closer to ovulation.
• If you are unsure about cycle length or have irregular bleeding.

If the purpose is to avoid pregnancy, menstruation is therefore not a method of "safety" in itself.

There are situations where pregnancy is practically impossible, but this typically requires a medical assessment or a clear biological reason.

If you suspect reduced fertility, it may be relevant to talk to your doctor about an evaluation. As a general guideline, it is often recommended to seek an assessment if pregnancy is not achieved after approximately one year of regular unprotected intercourse (often sooner for older individuals or those with known risk factors).

If you want more control over "when you can't get pregnant," it's about becoming better at identifying ovulation and cycle variations.

• Cycle app as a logbook (use it as a support, not as a definitive answer).
• LH tests to indicate impending ovulation.
• Body signs such as changes in cervical mucus.
• Basal body temperature (BBT) to see a pattern after ovulation.

No home method is perfect, and if you want reliable contraception, it's a good idea to choose a proven form of contraception and seek advice if needed.

Sources (selection): Sundhed.dk (Patienthåndbogen) on safe periods and contraception, as well as general fertility information from Danish health portals such as Med24.dk and Libero.dk (information on ovulation and fertility).