Методы определения фаз менструального цикла и планирования семьи.

Methods to determine menstrual phases
Systems of fertility awareness may be referred to as fertility awareness–based methods; the term Fertility Awareness Method (FAM) refers specifically to the system taught by Toni Weschler. The term natural family planning is sometimes used to refer to any use of fertility awareness methods, the lactational amenorrhea method and periodic abstinence during fertile times. A method of fertility awareness may be used by natural family planning users to identify these fertile times. Women who are breastfeeding a child and wish to avoid pregnancy may be able to practice the lactational amenorrhea method. The lactational amenorrhea method is distinct from fertility awareness, but because it also does not involve contraceptives, it is often presented alongside fertility awareness as a method of "natural" birth control. Within the Catholic Church and some Protestant denominations, the term natural family planning is often used to refer to Fertility Awareness pointing out it is the only method of family planning approved by the Church.

It is not known exactly when it was first discovered that women have predictable periods of fertility and infertility. It is already clearly stated in the Talmud tractate Niddah, that a woman only becomes pregnant in specific periods in the month, which seemingly refers to ovulation. St. Augustine wrote about periodic abstinence to avoid pregnancy in the year 388 (the Manichaeans attempted to use this method to remain childfree, and Augustine condemned their use of periodic abstinence). One book states that periodic abstinence was recommended "by a few secular thinkers since the mid nineteenth century," but the dominant force in the twentieth century popularization of fertility awareness based methods was the Roman Catholic Church. In 1905 Theodoor Hendrik van de Velde, a Dutch gynecologist showed that women only ovulate once per menstrual cycle. In the 1920s, Kyusaku Ogino, a Japanese gynecologist, and Hermann Knaus, from Austria, independently discovered that ovulation occurs about fourteen days before the next menstrual period. Ogino used his discovery to develop a formula for use in aiding infertile women to time intercourse to achieve pregnancy. In 1930, John Smulders, a Roman Catholic physician from the Netherlands, used this discovery to create a method for avoiding pregnancy. Smulders published his work with the Dutch Roman Catholic medical association, and this was the first formalized system for periodic abstinence: the rhythm method. This temperature method was found to be more effective at helping women avoid pregnancy than were calendar based methods. Over the next few decades, both systems became widely used among Catholic women. Two speeches delivered by Pope Pius XII in 1951 gave the highest form of recognition to the Catholic Church's approval—for couples who needed to avoid pregnancy—of these systems. In the early 1950s, John Billings discovered the relationship between cervical mucus and fertility while working for the Melbourne Catholic Family Welfare Bureau. Billings and several other physicians, including his wife, Dr. Evelyn Billings, studied this sign for a number of years, and by the late 1960s had performed clinical trials and begun to set up teaching centers around the world.

While Dr. Billings initially taught both the temperature and mucus signs, they encountered problems in teaching the temperature sign to largely illiterate populations in developing countries. In the 1970s they modified the method to rely on only mucus. and the Pope Paul VI Institute (1985), teaching a new mucus only system called the Creighton Model. Up until the 1980s, information about fertility awareness was only available from Catholic sources. The first secular teaching organization was the Fertility Awareness Center in New York, founded in 1981. Toni Weschler started teaching in 1982 and published the bestselling book Taking Charge of Your Fertility in 1995. Justisse was founded in 1987 in Edmonton, Canada. These secular organizations all teach symptothermal methods. Although the Catholic organizations are significantly larger than the secular fertility awareness movement, independent secular teachers have become increasingly common since the 1990s.

Development of fertility awareness methods is ongoing. In the late 1990s, the Institute for Reproductive Health at Georgetown University introduced two new methods. The Two Day Method, a mucus only system, and CycleBeads and iCycleBeads (the digital version), based on the Standard Days Method, are designed to be both effective and simple to teach, learn, and use. In 2019, Urrutia et al. released a study as well as interactive graph over viewing all studied fertility awareness based methods. Femtech companies such as Dot and Natural Cycles have also produced new studies and apps to help women avoid pregnancy. Natural Cycles is the first app of its kind to receive FDA approval.

Most menstrual cycles have several days at the beginning that are infertile (pre ovulatory infertility), a period of fertility, and then several days just before the next menstruation that are infertile (post ovulatory infertility). The first day of red bleeding is considered day one of the menstrual cycle. Different systems of fertility awareness calculate the fertile period in slightly different ways, using primary fertility signs, cycle history, or both.

The three primary signs of fertility are basal body temperature (BBT), cervical mucus, and cervical position. A woman practicing symptoms based fertility awareness may choose to observe one sign, two signs, or all three. Many women experience secondary fertility signs that correlate with certain phases of the menstrual cycle, such as abdominal pain and heaviness, back pain, breast tenderness, and mittelschmerz (ovulation pains).

This usually refers to a temperature reading collected when a person first wakes up in the morning (or after their longest sleep period of the day). The true BBT can only be obtained by continuous temperature monitoring through internally worn temperature sensors. In women, ovulation will trigger a rise in BBT between 0.2º and 0.5 °C. (0.5 and 1.°F) that lasts approximately until the next menstruation. This temperature shift may be used to determine the onset of post ovulatory infertility. (See ref. 30)

The appearance of cervical mucus and vulvar sensation are generally described together as two ways of observing the same sign. Cervical mucus is produced by the cervix, which connects the uterus to the vaginal canal. Fertile cervical mucus promotes sperm life by decreasing the acidity of the vagina, and also it helps guide sperm through the cervix and into the uterus. The production of fertile cervical mucus is caused by estrogen, the same hormone that prepares a woman's body for ovulation. By observing her cervical mucus and paying attention to the sensation as it passes the vulva, a woman can detect when her body is gearing up for ovulation, and also when ovulation has passed. When ovulation occurs, estrogen production drops slightly and progesterone starts to rise. The rise in progesterone causes a distinct change in the quantity and quality of mucus observed at the vulva.

The cervix changes position in response to the same hormones that cause cervical mucus to be produced and to dry up. When a woman is in an infertile phase of her cycle, the cervix will be low in the vaginal canal; it will feel firm to the touch (like the tip of a person's nose); and the os—the opening in the cervix—will be relatively small, or "closed". As a woman becomes more fertile, the cervix will rise higher in the vaginal canal, it will become softer to the touch (more like a person's lips), and the os will become more open. After ovulation has occurred, the cervix will revert to its infertile position.

Calendar based systems determine both pre ovulatory and post ovulatory infertility based on cycle history. When used to avoid pregnancy, these systems have higher perfect use failure rates than symptoms based systems but are still comparable with barrier methods, such as diaphragms and cervical caps. Mucus and temperature based methods used to determine post ovulatory infertility, when used to avoid conception, result in very low perfect use pregnancy rates. However, mucus and temperature systems have certain limitations in determining pre ovulatory infertility. A temperature record alone provides no guide to fertility or infertility before ovulation occurs. Determination of pre ovulatory infertility may be done by observing the absence of fertile cervical mucus; however, this results in a higher failure rate than that seen in the period of post ovulatory infertility. Relying only on mucus observation also means that unprotected sexual intercourse is not allowed during menstruation, since any mucus would be obscured. The use of certain calendar rules to determine the length of the pre ovulatory infertile phase allows unprotected intercourse during the first few days of the menstrual cycle while maintaining a very low risk of pregnancy. With mucus only methods, there is a possibility of incorrectly identifying mid cycle or anovulatory bleeding as menstruation. Keeping a basal body temperature chart enables accurate identification of menstruation, when pre ovulatory calendar rules may be reliably applied. In temperature only systems, a calendar rule may be relied on alone to determine pre ovulatory infertility. In symptothermal systems, the calendar rule is cross checked by mucus records: observation of fertile cervical mucus overrides any calendar determined infertility. Or, a calendar rule may require calculation, for example holding that the length of the pre ovulatory infertile phase is equal to the length of a woman's shortest cycle minus 21 days. Rather than being tied to cycle length, a calendar rule may be determined from the cycle day on which a woman observes a thermal shift. One system has the length of the pre ovulatory infertile phase equal to a woman's earliest historical day of temperature rise minus seven days.

Ovulation predictor kits can detect imminent ovulation from the concentration of luteinizing hormone (LH) in a woman's urine. A positive ovulation predictor kit result is usually followed by ovulation within 12–36 hours. Saliva microscopes, when correctly used, can detect ferning structures in the saliva that precede ovulation. Ferning is usually detected beginning three days before ovulation, and continuing until ovulation has occurred. During this window, ferning structures occur in cervical mucus as well as saliva. Computerized fertility monitors, such as Lady Comp, are available under various brand names. These monitors may use BBT only systems, they may analyze urine test strips, they may use symptothermal observations, they may monitor the electrical resistance of saliva and vaginal fluids, or a combination of any of these factors. A symptohormonal method of fertility awareness method developed at Marquette University uses the ClearBlue Easy fertility monitor to determine the fertile window. The monitor measures estrogen and LH to determine the peak day. This method is also applicable during postpartum, breastfeeding, and perimenopause, and requires less abstinence than other fertility awareness method methods. Some couples prefer this method because the monitor reading is objective and is not affected by sleep quality as basal body temperature can be.

There are no drug related side effects to ferility awareness. For women with very irregular cycles—such as those common during breastfeeding, perimenopause, or with hormonal diseases such as PCOS—abstinence or the use of barriers may be required for months at a time. Typical use effectiveness is lower than most other methods. Fertility awareness does not protect against sexually transmitted disease.

Regular menstrual cycles are sometimes taken as evidence that a woman is ovulating normally, and irregular cycles as evidence she is not. However, many women with irregular cycles do ovulate normally, and some with regular cycles are actually anovulatory or have a luteal phase defect. Records of basal body temperatures, especially, but also of cervical mucus and position, can be used to accurately determine if a woman is ovulating, and if the length of the post ovulatory (luteal) phase of her menstrual cycle is sufficient to sustain a pregnancy. Fertile cervical mucus is important in creating an environment that allows sperm to pass through the cervix and into the fallopian tubes where they wait for ovulation. Fertility charts can help diagnose hostile cervical mucus, a common cause of infertility. If this condition is diagnosed, some sources suggest taking guaifenesin in the few days before ovulation to thin out the mucus.

Pregnancy tests are not accurate until 1–2 weeks after ovulation. Knowing an estimated date of ovulation can prevent a woman from getting false negative results due to testing too early. Also, 18 consecutive days of elevated temperatures means a woman is almost certainly pregnant. Estimated ovulation dates from fertility charts are a more accurate method of estimating gestational age than the traditional pregnancy wheel or last menstrual period (LMP) method of tracking menstrual periods. Because of high rates of very early miscarriage (25% of pregnancies are lost within the first six weeks since the woman's last menstrual period), the methods used to detect pregnancy may lead to bias in conception rates. Less sensitive methods will detect lower conception rates, because they miss the conceptions that resulted in early pregnancy loss.