In most cases, the female body experiences a period (menstruation) once a month. The first day of menstruation also marks the beginning of a new cycle, which for most women lasts about 28 days. However, the exact cycle length varies, and shorter cycles of only 25 days or longer cycles of up to 35 days are completely normal (1). Whether or not you are actively trying to conceive, it is worthwhile to take a closer look at the complex processes that take place in the female body during the cycle.

Hormonal changes as preparation for ovulation

The cycle begins when the uterine lining built up during the previous cycle is shed and expelled through menstruation (1). Starting around day 5 of the cycle, a new phase begins: the hormone FSH causes new follicles to mature in the ovaries (2). These follicles help increase estrogen levels. (3) The rise in estrogen regenerates the uterine lining and prepares it for a potential pregnancy. After a few days, one dominant follicle develops, containing a single egg cell. Around days 12 to 14 of the cycle, hormone levels shift: the amount of estrogen—which had been responsible for regenerating the uterine lining—drops, while the hormone LH increases, triggering ovulation (2).

Ovulation marks the beginning of the second half of the cycle

During ovulation, the dominant follicle in one of the ovaries releases the matured egg. The egg leaves the ovary and travels through the fallopian tube toward the uterus. This is the ideal time to conceive: the lifespan of an egg is about 24 hours. Within this timeframe, it must be fertilized by sperm for pregnancy to occur.

Because sperm can survive in the female body for about three—sometimes up to six—days (4), waiting for ovulation, the fertile window includes both the days leading up to ovulation and the 24 hours afterward (5). If fertilization occurs, the egg implants into the uterine lining. If not, the uterine lining is shed at the end of the cycle with menstruation, marking the start of a new cycle (5).

Determining ovulation and fertile days

Ovulation usually occurs in the middle of the cycle. For a regular 28-day cycle, this would be around day 14. However, many factors can influence the cycle and thus the timing of ovulation—such as life stage, stress, medication use, or other external influences (2). Because every woman’s cycle is individual and can vary from cycle to cycle, no universal and reliable timing can be given (6)—it requires an individual understanding of one’s own body.

Body signals that help identify fertile days

Even though there is no universal rule, by observing body signals it is possible to find out individually when ovulation occurs and when the fertile days are. One indicator is the basal body temperature—the body’s resting temperature—which rises slightly after ovulation (7). The most reliable way to measure it is in the morning, right after waking and before getting out of bed.

Cervical mucus, secreted by small glands in the cervix (cervix uteri), is another signal (8). In the days before ovulation, the amount of mucus increases, and it becomes thinner, clearer, and more elastic. When examined, it may stretch like threads between the fingers (9)—a sign that ovulation is imminent. After ovulation, the mucus changes again and becomes thicker (4).

Determining fertile days with the symptothermal method

To know exactly when your fertile days occur and when fertilization is most likely, it is very helpful to get to know your body and the signals it sends.

With the symptothermal method, you regularly evaluate multiple body signals according to set rules to determine your fertile and infertile days.

The Ovy App and the Ovy Bluetooth Thermometer support this evaluation: by carefully documenting your basal temperature together with another marker such as cervical mucus quality, you can quickly determine which phase of the cycle you are in and how high the chance of pregnancy is. This way, you and your partner can time the perfect moment and increase the likelihood of fulfilling your wish to have children and start a family.

You might also be interested in these articles