Symptothermal Contraception

Definition/Introduction

Symptothermal contraception or fertility awareness-based methods (FABMs) of family planning are birth control methods in which women collect information to inform themselves of their fertile window, the days of the cycle with the highest fecundity.[1] These methods depend on observations of signs and symptoms that correlate with different hormone levels as indicators for an approximate timeframe when ovulation is likely to occur. Typical data may include 1 or more of the following: menstrual dates, basal body temperature (BBT), cervical mucus or position, and urinary hormone metabolites.[1] Due to the data collection that the patient requires, symptothermal contraception is commonly referred to as a "fertility-awareness" contraceptive method.[2] FABMs of family planning incorporate barrier methods, such as condoms, spermicidal gel, diaphragms, and withdrawal use during the fertile window. The use of these barriers distinguishes FABMs of family planning from natural family planning, which allows only abstinence during the fertile days.[3]

Most women experience an increase in their BBT of 0.5°F (0.3°C) shortly after ovulation. This increase in temperature is due to an increase in the release of both progesterone and estrogen by the corpus luteum during the luteal phase of the menstrual cycle. This increase in temperature persists until 1 to 2 days prior to menstruation.[3][4] The most fertile days of the cycle are the 2 to 3 days before this increase in temperature, during which ovulation most likely occurs.[5] A thermal nadir, the lowest BBT of the cycle, typically occurs the day before ovulation. Once BBT has persistently increased, ovulation has occurred, and the fertile window is over.[3] BBT is defined as the lowest natural body temperature recorded after a period of rest in the absence of pathology. The individual measures their BBT with a thermometer every morning upon awakening. The temperature must be recorded at approximately the same time each day.[6] The fertile windows can also be predicted based on algorithmic calculations from previous cycles.[3] The woman may prevent conception by avoiding sexual intercourse or using a barrier method during this time period.[7] Women are recommended to abstain from sexual intercourse 2 to 3 days prior to the expected increase in their body temperature and up to 3 days after its initial increase. The male partner's role in the FABMs of contraception cannot be overlooked since abstinence and condom or other barrier use are necessary for these methods to be effective.[3]

The person may also evaluate their cervical mucus or fluid (secretions) and its texture, consistency, and color daily. Adding a sign of estrogenic activity, like cervical mucus or urinary estrogen metabolites, increases the accuracy of identifying the fertile window compared to BBT measurements alone.[8] Cervical mucus either promotes or prohibits the passage of sperm during various times of the menstrual cycle.[3] At the beginning of the menstrual cycle, cervical mucus is tacky or viscid in nature. During the fertile period of the menstrual cycle, the cervical mucus is clear, abundant, and stretchy. This consistency of cervical mucus is present only during the fertile window.[3] It can be stretched between 2 fingers to a length of at least 6 cm due to an increase in estrogen at the end of the follicular phase.[9] This mucus consistency is meant to facilitate sperm mobilization for the process of fertilization. The aforementioned changes in cervical mucus can be detected approximately 4 to 7 days before ovulation.[4]

To reliably predict the upcoming menstrual cycles, it has been suggested that data collection should be done for approximately 6 to 12 cycles.[9] Using all of this information, the woman may then chart her menstrual cycle and determine which days they are in the luteal phase, the follicular phase, and which day ovulation is most likely to occur. The woman may then be able to determine their "fertile window," which is the period of days around ovulation when conception is most likely to occur.[10] The ovum remains able to be fertilized for 12 to 24 hours after ovulation. Sperm can live for up to 5 days after deposition in the female genital tract. These 2 considerations result in a fertile window of approximately 6 days. The highest chance of achieving pregnancy occurs in the 2 days before ovulation. Since a person does not usually ovulate on the same day with every cycle, the fertile window is considered to be longer than the actual 6 days with the FABMs of contraception.[3]

Tracking menstrual cycle length is another component that may be used in FABMs of contraception. Ovulation occurs 9 to 16 days prior to the end of a menstrual cycle. For example, in a person who has menstrual cycles that range from 26 to 32 days in length, the fertile window is likely to be days 8 through 19.[3] By tracking urinary hormones, specifically luteinizing hormone, and possibly estradiol, progesterone, and pregnanediol glucuronide, the completion of the fertile window may be appreciated. However, these urinary tests may not help predict the beginning of the fertile window.[3]

Many fertility-tracking apps have become popular for use in tracking cycles for people using symptothermal contraception. These apps help to identify the fertile window in order to avoid pregnancy. However, several reviews have found that these apps have not successfully predicted the fertile window and little evidence-based research supports their use. Many of these fertility-tracking apps have not been shown to be successful in pregnancy prevention. Additionally, when a comparison was made between apps, there was a large variation in the fertile window start day and fertile window end day for a specific patient's data. Furthermore, many apps failed to identify all days that likely fall within the physiologically fertile window. A study of 40 apps and technologies found that only 4 could effectively predict fertility windows. Therefore, patients may experience unintended pregnancies because they are unknowingly relying on technology that is not evidence-based.[8]

Issues of Concern