Fertility awareness (FA) refers to a set of practices used to determine the fertile and infertile phases of a woman's
menstrual cycleThe menstrual cycle is a cycle of physiological changes that occurs in fertile females. Overt menstruation occurs primarily in humans and close evolutionary relatives such as chimpanzees...
. Fertility awareness methods may be used to
avoid pregnancyBirth control is a regimen of one or more actions, devices, sexual practices, or medications followed in order to deliberately prevent or reduce the likelihood of pregnancy or childbirth...
, to achieve pregnancy, or as a way to monitor gynecological health.
Methods of identifying infertile days have been used for over a thousand years, but scientific knowledge gained during the past century has greatly increased the accuracy of these systems. From 1930 to 1980, all research and promotion of fertility awareness was done by those associated with the
Roman Catholic ChurchThe Catholic Church, also known as the Roman Catholic Church, is the world's largest Christian church. With more than a billion members, over half of all Christians and more than one-sixth of the world's population, the Catholic Church is a communion of the Western, or Latin Rite Church, and...
. Fertility awareness organizations continue to be predominately Catholic, but some secular organizations now exist.
Systems of fertility awareness rely on observation of changes in one or more of the primary fertility signs (
basal body temperatureBasal body temperature is the lowest temperature attained by the body during rest . It is generally measured immediately after awakening and before any physical activity has been undertaken, although the temperature measured at that time is somewhat higher than the true basal body temperature...
, cervical mucus, and cervical position), records of menstrual cycle length, or both. Other signs may also be observed: these include breast tenderness and
mittelschmerzMittelschmerz is a medical term for "ovulation pain" or "midcycle pain". About 20% of women experience mittelschmerz, some every cycle, some intermittently.-Symptoms and diagnosis:...
(ovulation pains), urine analysis strips known as ovulation predictor kits (OPKs), and microscopic examination of saliva or cervical fluid. Also available are computerized fertility monitors.
Terminology
Symptoms-based methods involve tracking one or more of the three primary fertility signs -
basal body temperatureBasal body temperature is the lowest temperature attained by the body during rest . It is generally measured immediately after awakening and before any physical activity has been undertaken, although the temperature measured at that time is somewhat higher than the true basal body temperature...
, cervical mucus, and cervical position. Systems relying exclusively on cervical mucus include the
Billings Ovulation MethodThe Billings ovulation method is a method which women use to monitor their fertility, by identifying when they are fertile and when they are infertile during each menstrual cycle. Users pay attention to the sensation at their vulva, and the appearance of any vaginal discharge...
, the
Creighton ModelThe Creighton Model FertilityCare System is a form of natural family planning which involves identifying the fertile period during a woman's menstrual cycle. The Creighton Model was developed by Thomas Hilgers, the founder and director of the Pope Paul VI Institute...
, and the Two-Day Method. Symptothermal methods combine observations of basal body temperature (BBT), cervical mucus, and sometimes cervical position. Calendar-based methods rely only on a history of cycle lengths. While the
World Health OrganizationThe World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health...
classifies both symptoms-based and calendar-based methods as "fertility awareness", some teachers of symptoms-based methods do
not consider calendar-based methods to be fertility awareness.
Systems of fertility awareness may be referred to as fertility awareness-based methods (FAB methods); the term Fertility Awareness Method (FAM) refers specifically to the system taught by
Toni WeschlerToni Weschler is the author of the bestselling book on women's health and fertility, Taking Charge of Your Fertility: The Definitive Guide to Natural Birth Control, Pregnancy Achievement, and Reproductive Health as well as the new "Cycle Savvy: The Smart Teen's Guide to the Mysteries of Her Body...
. The term
natural family planningNatural family planning is a term referring to the family planning methods approved by the Roman Catholic Church. In accordance with the requirements for sexual behavior in keeping with the dignity of the human person, as maintained by this church, NFP excludes the use of other methods of birth...
" (NFP) is sometimes used to refer to any use of FA methods. However, NFP specifically refers to practices that are approved by the
Roman Catholic ChurchThe Catholic Church, also known as the Roman Catholic Church, is the world's largest Christian church. With more than a billion members, over half of all Christians and more than one-sixth of the world's population, the Catholic Church is a communion of the Western, or Latin Rite Church, and...
:
breastfeeding infertilityThe lactational amenorrhea method is a method of avoiding pregnancies which is based on the natural postpartum infertility that occurs when a woman is amenorrheic and fully breastfeeding...
, and periodic
abstinenceAbstinence is a voluntary restraint from indulging a desire or appetite for certain bodily activities that are widely experienced as giving pleasure. Most frequently, the term refers to abstention from sexual intercourse, alcohol or food. The practice can arise from religious prohibitions or...
during fertile times. A method of FA may be used by NFP 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 methodThe lactational amenorrhea method is a method of avoiding pregnancies which is based on the natural postpartum infertility that occurs when a woman is amenorrheic and fully breastfeeding...
(LAM). LAM is distinct from fertility awareness, but because it also does not involve devices or chemicals, it is often presented alongside FA as a method of natural birth control.
Development of calendar-based methods
It is not known exactly when it was first discovered that women have predictable periods of fertility and infertility.
St. AugustineAugustine of Hippo , Bishop of Hippo Regius, also known as St. Augustine or St. Austin, was an Algerian Berber philosopher and theologian....
wrote about periodic abstinence to avoid pregnancy in the year 388 (the Manichaeans attempted to use this method to remain
childfreeChildfree is a term used to describe individuals who neither have children nor desire to have children. An alternative term is childless by choice....
, 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 ChurchThe Catholic Church, also known as the Roman Catholic Church, is the world's largest Christian church. With more than a billion members, over half of all Christians and more than one-sixth of the world's population, the Catholic Church is a communion of the Western, or Latin Rite Church, and...
.
In 1905
Theodoor Hendrik van de VeldeTheodoor Hendrik van de Velde was a Dutch physician and gynæcologist who served as Director at the Gynæcological Institute in Haarlem. His 1926 book Het volkomen huwelijk made him an instant international celebrity. The book advocated knowledge and sensuality in erotic life...
, a Dutch gynecologist, showed that women only ovulate once per menstrual cycle. In the 1920s,
Kyusaku Oginowas a Japanese doctor specializing in obstetrics and gynecology.His natural father's family name was Nakamura, but Kyusaku was adopted by the Ogino family in 1901....
, 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, 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.
Introduction of temperature and cervical mucus signs
In the 1930s, Rev. Wilhelm Hillebrand, a Catholic priest in Germany, developed a system for avoiding pregnancy based on basal body temperature. This temperature method was found to be more effective at helping women avoid pregnancy than calendar-based methods. Over the next few decades, both systems became widely used among Catholic women. Two speeches delivered by
Pope Pius XIIPope Pius XII , born Eugenio Maria Giuseppe Giovanni Pacelli , reigned as the 260th Pope, head of the Catholic Church and sovereign of Vatican City, from 2 March 1939 until his death in 1958....
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,
Dr. John BillingsDr. John Billings, KCSG AM was an Australian doctor who pioneered the natural method of family planning known variously as the Billings Ovulation Method, the Ovulation Method, or the Billings Method....
discovered the relationship between cervical mucus and fertility while working for the Melbourne Catholic Family Welfare Bureau. Dr. Billings and several other physicians 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.
First symptoms-based teaching organizations
While the 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. The international organization founded by Dr. Billings is now known as the World Organization Ovulation Method Billings (WOOMB).
The first organization to teach a symptothermal method was founded in 1971. John and Sheila Kippley, lay Catholics, joined with Dr. Konald Prem in teaching an observational method that relied on all three signs: temperature, mucus, and also cervical position. Their organization is now called Couple to Couple League International. The next decade saw the founding of other now-large Catholic organizations — Family of the Americas (1977), teaching the Billings method, 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 WeschlerToni Weschler is the author of the bestselling book on women's health and fertility, Taking Charge of Your Fertility: The Definitive Guide to Natural Birth Control, Pregnancy Achievement, and Reproductive Health as well as the new "Cycle Savvy: The Smart Teen's Guide to the Mysteries of Her Body...
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 throughout the 1990s and 2000s.
Ongoing development
Development of fertility awareness methods is ongoing. In the late 1990s, the Institute for Reproductive Health at
Georgetown UniversityGeorgetown University is a Jesuit private university located in Georgetown, Washington, D.C. Father John Carroll founded the school in 1789, though its roots extend back to 1634. While the school struggled financially in its early years, Georgetown expanded into a branched university after the...
introduced two new methods. The Two-Day Method, a mucus-only system, and CycleBeads, a variant of the Rhythm Method, are designed to be both effective and very simple to teach, learn, and use.
Fertility signs
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.
Primary signs
The three primary fertility signs 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.
Basal body temperatureBasal body temperature is the lowest temperature attained by the body during rest . It is generally measured immediately after awakening and before any physical activity has been undertaken, although the temperature measured at that time is somewhat higher than the true basal body temperature...
is a person’s temperature taken when they first wake up in the morning (or after their longest sleep period of the day). In women,
ovulationOvulation is the process in the females menstrual cycle by which a mature ovarian follicle ruptures and discharges an ovum that participates in reproduction...
will trigger a rise in BBT between 0.3 and 0.9 °C (0.5 and 1.6 °F) that lasts approximately until the next menstruation. This temperature shift may be used to determine the onset of post-ovulatory infertility.
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 separates the uterus from the vaginal canal. Fertile cervical mucus promotes sperm life by decreasing the acidity of the vagina, and also helps guide sperm through the cervix and into the uterus.
The production of fertile cervical mucus is caused by the same hormone (estrogen) 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
cervixThe cervix is the lower, narrow portion of the uterus where it joins with the top end of the vagina. It is cylindrical or conical in shape and protrudes through the upper anterior vaginal wall. Approximately half its length is visible with appropriate medical equipment; the remainder lies above...
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.
Cycle history
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 to barrier methods such as
diaphragmsThe diaphragm is a cervical barrier type of birth control. It is a soft latex or silicone dome with a spring molded into the rim. The spring creates a seal against the walls of the vagina.-Use:...
and
cervical capThe cervical cap is form of barrier contraception. A cervical cap fits over the cervix and blocks sperm from entering the uterus through the external orifice of the uterus, called the os...
s.
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
menstruationMenstruation is the shedding of the uterine lining . It occurs on a regular basis in reproductive-age females of certain mammal species. Overt menstruation is found primarily in humans and close evolutionary relatives such as chimpanzees...
, since any mucus would be obscured.
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 BBT 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.
Calendar rules may set a standard number of days, specifying that (depending on a woman's past cycle lengths) the first three to six days of each menstrual cycle are considered infertile. 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 twenty-one 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.
Secondary signs
Many women experience secondary fertility signs that correlate with certain phases of the menstrual cycle. Examples include
abdominal painAbdominal pain can be one of the symptoms associated with transient disorders or serious disease. Making a definitive diagnosis of the cause of abdominal pain can be difficult, because many diseases can result in this symptom. Abdominal pain is a common problem...
and heaviness,
back painBack pain is pain felt in the back that usually originates from the muscles, nerves, bones, joints or other structures in the spine....
, breast tenderness and
mittelschmerzMittelschmerz is a medical term for "ovulation pain" or "midcycle pain". About 20% of women experience mittelschmerz, some every cycle, some intermittently.-Symptoms and diagnosis:...
(ovulation pains).
Other techniques
Ovulation predictor kits (OPKs) can detect imminent ovulation from the concentration of lutenizing hormone (LH) in a woman’s urine. A positive OPK 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.
Fertility monitorA fertility monitor is a computerized device used for fertility awareness. Some brands are marketed only to assist in pregnancy achievement, while other brands are advertised for both pregnancy achievement and as birth control...
s are available under various brand names. These monitors may use BBT-only systems, they may analyze urine test strips, or they may monitor the electrical resistance of saliva and vaginal fluids.
Benefits and drawbacks
Fertility awareness has a number of unique characteristics:
- FA can be used to monitor reproductive health. Changes in the cycle can alert the user to emerging gynecological problems. FA can also be used to aid in diagnosing known gynecological problems such as infertility.
- FA is versatile: it may be used to avoid pregnancy or to aid in conception.
- FA can be used by all women throughout their reproductive life, regardless of whether a woman is approaching menopause, is breastfeeding, or experiencing irregular cycles for other reasons.
- Use of FA can give insight to the workings of women's bodies, and may allow women to take greater control of their own fertility.
- Some symptoms-based forms of fertility awareness require observation or touching of cervical mucus, an activity with which some women are not comfortable. Some practitioners prefer to use the term "cervical fluid" to refer to cervical mucus, in an attempt to make the subject more palatable to these women.
- Some drugs, such as decongestants, can change cervical mucus. In women taking these drugs, the mucus sign may not accurately indicate fertility.
- Some symptoms-based methods require tracking of basal body temperatures. Because irregular sleep can interfere with the accuracy of basal body temperatures, shift workers and those with very young children, for example, might not be able to use those methods.
As birth control
By restricting unprotected sexual intercourse to the infertile portion of the menstrual cycle, a woman and her partner can prevent pregnancy. During the fertile portion of the menstrual cycle, the couple may use
barrier contraceptionBarrier contraception methods prevent pregnancy by physically preventing sperm from entering the uterus.-History:The earliest recorded barrier methods are those of stem pessaries, found in Egypt. The diaphragm and reusable condoms became common after the invention of rubber vulcanization in the...
or abstain from sexual intercourse.
Advantages
- There are no drug-related side effects to FA. There are no side effects at all, besides those that may occur from inserting fingers into the vagina for cervical observation (as some FA methods recommend).
- FA is free or very low-cost. Users may buy a chart, calendar, basal thermometer, or software, or employ a coach. The direct costs are low when compared to other methods.
- FA can be used with barrier contraception
Barrier contraception methods prevent pregnancy by physically preventing sperm from entering the uterus.-History:The earliest recorded barrier methods are those of stem pessaries, found in Egypt. The diaphragm and reusable condoms became common after the invention of rubber vulcanization in the...
so that intercourse may continue through the fertile period. Unlike barrier use without FA, practicing FA can allow couples to use barrier contraception only when necessary.
Disadvantages
- Use of a barrier method is required on fertile days, otherwise the couple must abstain. To reduce pregnancy risk to below 1% per year, there are an average of 13 days where abstinence or barriers must be used during each cycle. For women with very irregular cycles — such as those common during breastfeeding, perimenopause, or with hormonal diseases such as PCOS
Polycystic ovary syndrome is an endocrine disorder that affects approximately 5% of all women.It occurs amongst all races and nationalities, is the most common hormonal disorder among women of reproductive age, and is a leading cause of infertility.The principal features are obesity, anovulation ,...
- abstinence or the use of barriers may be required for months at a time. Many couples may not have the motivation or discipline to abstain or use barriers for long periods of time.
- Fertility awareness does not protect against sexually transmitted disease
A sexually transmitted disease , also known as sexually transmitted infection or venereal disease , is an illness that has a significant probability of transmission between humans or animals by means of sexual contact, including vaginal intercourse, oral sex, and anal sex...
.
Effectiveness
The effectiveness of fertility awareness, as of most forms of
contraceptionBirth control is a regimen of one or more actions, devices, sexual practices, or medications followed in order to deliberately prevent or reduce the likelihood of pregnancy or childbirth...
, can be assessed two ways.
Perfect use or
method effectiveness rates only include people who follow all observational rules, correctly identify the fertile phase, and refrain from unprotected intercourse on days identified as fertile.
Actual use, or
typical use effectiveness rates are of all women relying on fertility awareness to avoid pregnancy, including those who fail to meet the "perfect use" criteria. Rates are generally presented for the first year of use. Most commonly the
Pearl IndexThe Pearl Index, also called the Pearl rate, is the most common technique used in clinical trials for reporting the effectiveness of a birth control method.-Calculation and usage:...
is used to calculate effectiveness rates, but some studies use
decrement tableDecrement tables, also called life table methods, are used to calculate the probability of certain events.-Birth control:Life table methods are often used to study birth control effectiveness...
s.
The failure rate of fertility awareness varies widely depending on the system used to identify fertile days, the instructional method, and the population being studied. Some studies have found actual failure rates of 25% per year or higher. At least one study has found a failure rate of less than 1% per year with continuous intensive coaching and monthly review, and several studies have found actual failure rates of 2-3% per year.
When used correctly and consistently with ongoing coaching, some studies have shown some forms of FA to be 99% effective, the same as oral contraceptives.
From
Contraceptive Technology:
- Post-ovulation methods (i.e. abstaining from intercourse from menstruation until after ovulation) have a method failure rate of 1% per year.
- The symptothermo method has a method failure rate of 2% per year.
- The cervical mucus-only methods have a method failure rate of 3% per year.
- Calendar rhythm has a method failure rate of 9% per year.
- The Standard Days Method has a method failure rate of 5% per year.
Reasons for lower typical-use effectiveness
Several factors account for typical use effectiveness being lower than perfect use effectiveness:
- mistakes on the part of those providing instructions on how to use the method (instructor providing incorrect or incomplete information on the rule system)
- mistakes on the part of the user (misunderstanding of rules, mistakes in charting)
- conscious user non-compliance with instructions (having unprotected intercourse on a day identified as fertile)
The most common reason for the lower actual effectiveness is not mistakes on the part of instructors or users, but conscious user non-compliance, i.e., the couple knowing that the woman is likely to be fertile at the time, but engaging in sexual intercourse nonetheless. This is similar to failures of barrier methods, which are primarily caused by non-use of the method.
Intercourse timing
A study by Barrett and Marshall has shown that random acts of intercourse achieve a 24% pregnancy rate per cycle. That study also found that timed intercourse based on information from a BBT-only method of FA increased pregnancy rates to 31%-68%.
Studies of cervical-mucus methods of fertility awareness have found pregnancy rates of 67%-81% in the first cycle if intercourse occurred on the Peak Day of the mucus sign.
Because of high rates of very early
miscarriageMiscarriage or spontaneous abortion is the spontaneous end of a pregnancy at a stage where the embryo or fetus is incapable of surviving, generally defined in humans at prior to 20 weeks of gestation...
(25% of pregnancies are lost within the first six weeks since the woman's last menstrual period, or
LMPGestational age is the age of an embryo or fetus . In humans, a common method of calculating gestational age starts counting either from the first day of the woman's last menstrual period or from 14 days before conception . Counting from the first day of the LMP involves the assumption that...
), 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. A Chinese study of couples practicing random intercourse to achieve pregnancy used very sensitive pregnancy tests to detect pregnancy. It found a 40% conception rate per cycle over the 12-month study period.
Problem diagnosis
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 annovulatory 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
guaifenesinGuaifenesin or guaiphenesin , also glyceryl guaiacolate, is an expectorant drug sold over the counter and usually taken by mouth to assist the bringing up of phlegm from the airways in acute respiratory tract infections.-History:Similar medicines derived from the guaiac tree were in use as a...
in the few days before ovulation to thin out the mucus.
Pregnancy testing and gestational age
Pregnancy testA pregnancy test attempts to determine whether or not a woman is pregnant. Records of attempts at pregnancy testing have been found as far back as the ancient Greek and ancient Egyptian cultures. Modern pregnancy tests look for chemical markers associated with pregnancy. These markers are found...
s 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 ageGestational age is the age of an embryo or fetus . In humans, a common method of calculating gestational age starts counting either from the first day of the woman's last menstrual period or from 14 days before conception . Counting from the first day of the LMP involves the assumption that...
than the traditional pregnancy wheel or last menstrual period (LMP) method of tracking menstrual periods.