Category: Research

The likelihood of spontaneous conception in subsequent cycles is important for a balanced management of infertility. Previous studies on time to pregnancy are mostly retrospective and biased because of exclusion of truly infertile couples. The study aim was to present a non‐parametric estimation of cumulative probabilities of conception (CPC) in natural family planning (NFP) users illustrating an ideal of human fertility potential. METHODS: A total of 346 women was observed who used NFP methods to conceive from their first cycle onwards.

The couples practising NFP make optimal use of their fertility potential by timed intercourse. The CPC were estimated for the total group and for couples who finally conceived by calculating Kaplan‐Meier survival rates. RESULTS: A total of 310 pregnancies occurred among the 346 women; the remaining 36 women (10.4%) did not conceive. Estimated CPC for the total group (n = 340 women) at one, three, six and 12 cycle(s) were 38, 68, 81 and 92% respectively. For those who finally conceived (truly fertile couples, n = 304 women), the respective pregnancy rates were 42, 75, 88 and 98% respectively.

Although the numbers of couples in both groups were similar, the impact of age on time to conception, as judged by the Wilcoxon test, was less in the truly fertile than in the total group. CONCLUSIONS: Most couples conceive within six cycles with timed intercourse. Thereafter, every second couple is probably either subfertile or infertile. CPC decline with age because heterogeneity in fecundity increases. In the subgroup of truly fertile couples, an age‐dependent decline in CPC is statistically less obvious because of high homogeneity, even with advancing age.

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Objectives: To provide specific estimates of the likely occurrence of the six fertile days (the “fertile window”) during the menstrual cycle.

Design: Prospective cohort study.

Participants: 221 healthy women who were planning a pregnancy.

Main outcome measures: The timing of ovulation in 696 menstrual cycles, estimated using urinary metabolites of oestrogen and progesterone.

Results: The fertile window occurred during a broad range of days in the menstrual cycle. On every day between days 6 and 21, women had at minimum a 10% probability of being in their fertile window. Women cannot predict a sporadic late ovulation; 4-6% of women whose cycles had not yet resumed were potentially fertile in the fifth week of their cycle.

Conclusions: In only about 30% of women is the fertile window entirely within the days of the menstrual cycle identified by clinical guidelines—that is, between days 10 and 17. Most women reach their fertile window earlier and others much later. Women should be advised that the timing of their fertile window can be highly unpredictable, even if their cycles are usually regular.

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Two studies have related the timing of sexual intercourse (relative to ovulation) to day-specific fecundability. The first was a study of Catholic couples practising natural family planning in London in the 1950s and 1960s and the second was of North Carolina couples attempting to become pregnant in the early 1980s. The former identified ovulation based on the ovulatory shift in the basal body temperature, while the latter used urinary assays of hormones.

We use a statistical model to correct for error in identifying ovulation and to re-estimate the length of the fertile window and day-specific fecundabilities. We estimate the same 6-day fertile interval in both studies after controlling for error. After adjusting for error both data sets showed the highest estimate of the probability of pregnancy on the day prior to ovulation and both fell close to zero after ovulation. Given that the fertile interval is before ovulation, methods that anticipate ovulation by several days (such as the assessment of cervical mucus) would be particularly useful for couples who want to time their intercourse either to avoid or facilitate conception

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The purposes of this investigation were to evaluate the characteristics of three consecutive menstrual cycles and to determine the frequency of luteal phase deficiency (LPD) and anovulation in a sample of sedentary and moderately exercising, regularly menstruating women.

For three consecutive menstrual cycles, subjects collected daily urine samples for analysis of FSH, estrone conjugates (E1C), pregnanediol-3-glucuronide (PdG), and creatinine (Cr). Sedentary (n = 11) and exercising (n = 24) groups were similar in age (27.0 ± 1.3 yr), weight (60.3 ± 3.1 kg), gynecological age (13.8 ± 1.2 yr), and menstrual cycle length (28.3 ± 0.8 days).

Menstrual cycles were classified by endocrine data as ovulatory, LPD, or anovulatory. No sedentary women (0%) had inconsistent menstrual cycle classifications from cycle to cycle, but 46% of the exercising women were inconsistent. The sample prevalence of LPD in the exercising women was 48%, and the 3-month sample incidence was 79%. In the sedentary women, 90% of all menstrual cycles were ovulatory (SedOvul; n = 28), whereas in the exercising women only 45% were ovulatory (ExOvul; n = 30); 43% were LPD (ExLPD; n = 28), and 12% were anovulatory (ExAnov; n = 8). In ExLPD cycles, the follicular phase was significantly longer (17.9 ± 0.7 days), and the luteal phase was significantly shorter (8.2 ± 0.5 days) compared to ExOvul (14.8 ± 0.9 and 12.9 ± 0.3 days) and SedOvul (15.9 ± 0.6 and 12.9 ± 0.4 days) cycles.

Luteal phase PdG excretion was lower (P < 0.001) in ExLPD (2.9 ± 0.3 μg/mg Cr) and ExAnov (0.8 ± 0.1 μg/mg Cr) cycles compared to SedOvul cycles (5.0 ± 0.4 μg/mg Cr). ExOvul cycles also had less (P < 0.01) PdG excretion during the luteal phase (3.7 ± 0.3 μg/mg Cr) than the SedOvul cycles. E1C excretion during follicular phase days 2–5 was lower (P = 0.05) in ExOvul, ExLPD, and ExAnov cycles compared to SedOvul cycles and remained lower (P < 0.02) in the ExLPD and ExAnov cycles during days 6–12.

The elevation in FSH during the luteal-follicular transition was lower (P < 0.007) in ExLPD (0.7 ± 0.1 ng/mg Cr) cycles compared to SedOvul and ExOvul cycles (1.0 ± 0.1 and 1.1 ± 0.1 ng/mg Cr, respectively). Energy balance and energy availability were lower (P < 0.05) in ExAnov cycles than in other menstrual cycle categories. The blunted elevation in FSH during the luteal-follicular transition in exercising women with LPD may explain their lower follicular estradiol levels. These alterations in FSH may act in concert with disrupted LH pulsatility as a primary and proximate factor in the high frequency of luteal phase and ovulatory disturbances in regularly menstruating, exercising women.

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We carried out a prospective study of 221 healthy women who were attempting pregnancy. During the study, women collected daily urine samples and kept daily records of intercourse.

Ovulation and early pregnancy losses were later identified by immunoassays of urinary human chorionic gonadotrophin and steroid metabolites. We have used these data to examine whether the risk of early pregnancy loss was higher with post-ovulatory ageing of the oocyte. 192 pregnancies were ranked by the probability that the oocyte might have aged before fertilization.

There was a statistically significant increase in the risk of early loss as the likelihood of oocyte ageing increased (P < 0.05). No similar risk was observed for clinical miscarriages. Post-ovulatory ageing of the oocyte prior to fertilization may cause early pregnancy failure in humans as it does in several other mammalian species.

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Eighty women attending for consultation at a tertiary referral fertility unit over a 3-month period were surveyed for their knowledge of fertility awareness and how they used this information to enhance their chances of conception. It was hypothesized that less than 50% of the subjects had an adequate understanding of when the fertile time occurred in their menstrual cycle. A questionnaire was completed anonymously by each subject and these were scored in 3 categories for fertility awareness by 2 independent Natural Family Planning teachers. Scores ranged from 0 for women who had no concept of fertility awareness, to 6 for women who were highly aware. The results showed that 26% (N = 21) of subjects had a score of 4 or greater which was considered as having an adequate understanding. The hypothesis was accepted, giving reason for concern about the effectiveness of consumer education at all levels of fertility investigation.

PIP: Fertility awareness was assessed in a survey of 80 women presenting over a 3-month period to a tertiary referral unit at the National Women’s Hospital in Auckland, New Zealand, for infertility investigation. It was hypothesized that less than 50% of menstruating women with a history of at least 2 years of infertility have an adequate understanding about the fertile time of their menstrual cycle. 60% of women had been trying to conceive for 2-3 years, 23% for 4-5 years, and 17% for more than 6 years. For 58% of clients, this was their first visit to a fertility clinic. 13% had attended a natural family planning (NFP) clinic previously. On the basis of questionnaire responses, participants were graded from 0 to 2 in each of the following 3 categories: 1) level of fertility symptom awareness (cervical mucus and ovulatory pain), 2) level of understanding of what these symptoms mean, and 3) level of use of this information to enhance conception. Only 21 women (26%) had a final score of 4 or greater–a predetermined cut-off considered indicative of adequate fertility awareness. The largest percentage of women (46%) had scores of 0-1. 80% of women with previous NFP instruction had adequate fertility awareness scores. These finding supported the study hypothesis of a generally poor level of fertility awareness among women presenting for treatment of infertility. Greater utilization of NFP clinics by general practitioners and specialists, as well as incorporation of NFP trained nurses into tertiary referral clinics, are recommended.

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Information about fertility awareness helps to fulfil the broader definition of the services many family planning clinics offer.

Although information about natural family planning is requested by a small number of clients seeking family planning advice, many more clients benefit from information about fertility awareness. Fertility awareness is far more than just basic reproductive anatomy and physiology; fertility awareness involves understanding basic information about fertility and reproduction, being able to apply it to oneself, and being able to discuss it with a partner or with a health professional. Fertility awareness is fundamental to understanding and making informed decisions about reproductive health and sexual health.

If clients have a better understanding of fertility awareness, they are in a stronger position to make informed decisions about how they wish to manage their reproductive and sexual health, for example:

(1) Fertility awareness information is used to help couples to plan pregnancies as well as to avoid them. This can be helpful to couples who are having difficulty conceiving, for the timing of intercourse or for the timing of some of the sub-fertility investigations.

(2) The information is also useful when helping couples to understand how each method of family planning works--how the family planning method interrupts normal fertility, how the method will fail if not used correctly, and how fertility returns when the method is discontinued.

(3) Women who are fully breastfeeding value the knowledge about reduced fertility, as do women during the perimenopausal years who value being given clear information about their declining fertility.

(4) When counselling couples about the importance of avoiding sexually transmitted diseases it is important they understand sexually transmitted diseases may damage their fertility.

(5) Couples who choose only to use a barrier method during the time they think the woman is fertile are a group who do not readily identify themselves to family planning providers. These couples often do not have adequate information about fertility awareness. Advances in technology and the understanding of ovulation, ovum and sperm survival have confirmed that the guidelines used to teach fertility awareness and natural family planning effectively identify the fertile phase of the menstrual cycle.

Serial ultrasound studies on the ovaries during the menstrual cycle have confirmed the accuracy of the hormonal assays in pinpointing the likely time of ovulation. Ultrasound studies have also shown that subjective observations of the alterations in cervical mucus and the basal body temperature rise are accurate indicators of the fertile phase.

Research on the chances of conception on each day of the menstrual cycle, using hormonal assays to estimate the time of ovulation, was carried out in 1994 by Weinberg and Wilcox. Their results showed that the timing of sexual intercourse, in relation to ovulation, strongly influences the chance of conception. Conception only occurred during a 6-day interval that ended on the estimated day of ovulation. The chances of conception fell to zero 24 hours after ovulation.

Several different methods of natural family planning are taught; some methods depend on only using one of the indicators of fertility, others are based on two or more indicators. The main indicators of fertility are: observing the cervical mucus, recording the basal body temperature, palpating the cervix and a calculation based on the cycle length. Research studies performed using a combination of the indicators of fertility show that the failure rate using a combination is less than most of the studies which use a single indicator. In each case the method failure is far lower than the user failure.

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BACKGROUND
The timing of sexual intercourse in relation to ovulation strongly influences the chance of conception, although the actual number of fertile days in a woman's menstrual cycle is uncertain. The timing of intercourse may also be associated with the sex of the baby.

METHODS
We recruited 221 healthy women who were planning to become pregnant. At the same time the women stopped using birth-control methods, they began collecting daily urine specimens and keeping daily records of whether they had sexual intercourse. We measured estrogen and progesterone metabolites in urine to estimate the day of ovulation.

RESULTS
In a total of 625 menstrual cycles for which the dates of ovulation could be estimated, 192 pregnancies were initiated, as indicated by increases in the urinary concentration of human chorionic gonadotropin around the expected time of implantation. Two thirds (n = 129) ended in live births. Conception occurred only when intercourse took place during a six-day period that ended on the estimated day of ovulation. The probability of conception ranged from 0.10 when intercourse occurred five days before ovulation to 0.33 when it occurred on the day of ovulation itself. There was no evident relation between the age of sperm and the viability of the conceptus, although only 6 percent of the pregnancies could be firmly attributed to sperm that were three or more days old. Cycles producing male and female babies had similar patterns of intercourse in relation to ovulation.

CONCLUSIONS
Among healthy women trying to conceive, nearly all pregnancies can be attributed to intercourse during a six-day period ending on the day of ovulation. For practical purposes, the timing of sexual intercourse in relation to ovulation has no influence on the sex of the baby.

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World Health Organisation: Task Force on Methods for the Determination of the Fertile Period, Special Programme of Research, Development and Research Training in Human Reproduction. World Health Organisation. Geneva, Switzerland. The intra and inter woman variation in nine physiological or biochemical indices of the fertile period has been studied over 58 menstrual cycles from 13 experienced users of the symptothermal method of family planning by periodic abstinence.

The time and duration of a possible fertile period have been determined by five methods (symptothermal, cervical mucus, basal body temperature plus calendar calculation, defined changes in the concentration of estrone-3-glucuronide and the ratio of estrone-3-glucuronide to pregnanediol-3a-glucuronide as determined by immunochemical tests on daily samples of early morning urine). The values were compared with a period of probable fertility (day of urinary luteotropin (LH) peak -3 to day of LH peak -2). The duration of the possible fertile period for each method (mean= standard deviation) was 13.4 (2.9), 11.9 (2.9), 11.8 (3.3), 9.3 (2.2), and 10.9 (2.3) days, respectively,while the percentage of the probable fertile periods covered entirely by each approach was 98%, 91%, 90%, 83%, and 84%, respectively. The results warrant the initiation of clinical traits to ascertain the practical value of the individual or combined tests for family planning and the management of infertility.Fertil Steril 39:647, 1983.

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