How to know the fertile period: signs, calculations and identification methods Credit: Disclosure For women trying to get pregnant, understanding their menstrual cycle is the first step. The fertile period corresponds to the days on which pregnancy is possible, and it is shorter than many people imagine: on average, it lasts between five and six days per cycle, with the day of ovulation being the day with the greatest chance of conception. Knowing how to identify this window depends on observation, calculation and, in some cases, resources that help confirm what the body is signaling. What is the fertile period Ovulation occurs when a mature egg is released from the ovary. This egg survives for 12 to 24 hours. Sperm, in turn, can survive in the female reproductive system for up to five days under favorable conditions. Therefore, the days leading up to ovulation are also considered fertile. In practice, the fertile period covers the day of ovulation and the five days before it. The most productive day, statistically, is the day before ovulation and the day it occurs. How to calculate the fertile period by the menstrual cycle The best known calculation is based on the regularity of the cycle. In a 28-day cycle, ovulation usually occurs around the 14th day, counting from the first day of menstruation. The fertile period, in this case, would range from the 10th to the 16th day approximately. For longer or shorter cycles, the reasoning adjusts: 14 days are subtracted from the total cycle to estimate the day of ovulation. In a 30-day cycle, for example, ovulation would tend to occur around the 16th day. The problem with this method is that it starts from an assumption of regularity that is not always confirmed. Factors such as stress, weight changes, illness or hormonal changes can shift ovulation from one cycle to another. Irregular cycles: what changes Irregular cycles make calculation by date unreliable. In these cases, monitoring physical signs and using ovulation tests are best suited to identify the fertile period. Some conditions that cause irregularity include: polycystic ovary syndrome hypothyroidism or hyperthyroidism significant weight changes recent use of hormonal contraceptives prolonged stress When cycles are very variable, medical evaluation helps understand if there is an underlying cause that needs attention. Supplementation before pregnancy Women who are planning to become pregnant may benefit from folic acid supplementation before conception. Starting use at least three months before pregnancy is associated with a reduced risk of neural tube defects in the baby, according to recommendations from the Ministry of Health and international organizations such as the WHO. Some dietary supplements can help restore ovulation, as well as acting on the female immune system and metabolism. Sopi, for women, as it contains folic acid, can help increase the fertilization rate. Supplements such as Ofolato, with folic acid, are indicated in this pre-conception period. For women looking for a more complete formulation with vitamins and minerals aimed at this phase, Ogestan Pré is one of the options available in pharmacies. Supplementation does not replace medical advice, but can be started alongside a pre-conception consultation. "Women who want to get pregnant and have not been successful, should seek medical assistance, so that the professional can understand the case. Supplements can help, but they do not replace medical analysis", explains Eliane Messias, pharmacist responsible for Rede Drogal. Body signals that indicate the fertile period The organism produces some observable changes during the fertile period. Among the most documented are: change in cervical mucus, which becomes more clear, stretchy, and similar to egg white slight increase in basal body temperature after ovulation feeling of heaviness or slight discomfort in the pelvic area increased libido in some cases more sensitive breasts These changes are not perceived in the same way by all women. Some easily identify changes in mucus; others do not notice any variation. Basal temperature: how to use Basal temperature is the resting body temperature, measured upon waking up, before any activity. After ovulation, progesterone causes this temperature to rise by at least 0.4°C, and it remains high until the start of the next menstruation. The basal temperature method does not predict ovulation: it confirms that it has already occurred. Therefore, it is more useful for those who want to understand the cycle pattern over time than for those who need to identify the fertile moment in real time. Daily recording for two or three cycles often reveals a pattern that, over time, helps you anticipate the days with the greatest chance. Cervical mucus: what to watch out for Monitoring cervical mucus, also called the Billings method, is one of the most studied resources to identify the fertile period. During the days leading up to ovulation, estrogen levels rise and stimulate the production of more fluid mucus, with an elastic and translucent appearance. This mucus has a direct physiological function: it facilitates sperm mobility and creates an environment favorable to fertilization. After ovulation, with the increase in progesterone, the mucus becomes thicker, opaque and less abundant, or disappears. Ovulation tests: how they work Ovulation tests detect the spike in luteinizing hormone, LH, in the urine. This peak occurs between 24 and 48 hours before ovulation and represents the most reliable sign that it is about to happen. Use is similar to that of a pregnancy test: the strip or device is exposed to urine and the result is read within minutes. The ideal is to perform the test at the same time every day, preferably between 10am and 8pm, avoiding urinating for at least two hours beforehand. For women with irregular cycles, the tests offer a more reliable reference than calculating by date, as they respond directly to what is happening in the body at that moment. When to seek medical advice Seeing a gynecologist is recommended when: cycles are very irregular or absent trying to get pregnant lasts more than 12 months without results, or more than 6 months for women over 35 years old there is a history of miscarriages there are signs of hormonal changes, such as excess hair, persistent acne or unexplained weight changes These cases may indicate conditions that interfere with ovulation and for which treatment is available. Identifying the fertile period is possible with observation and method The fertile period can be mapped with a combination of calculation, observation of physical signs and specific tests. No single method is infallible, but combining two or more features increases identification accuracy. For those who are at the beginning of this journey, recording the cycle for a few months helps to recognize patterns and make more informed decisions, whether to try for pregnancy or to better understand your own body. What are the first symptoms of pregnancy at the beginning? Eliane Messias Rodrigues, responsible pharmacist for Drogal. CRF/SP 43,895