The Many Phases of Fertility

It is possible to be perfectly fertile and not be able to get pregnant for years, especially if you haven’t learned how important it is to time conception. Because of this couples have been falsely labeled infertile.

Consider this. Couples who have no apparent problems with fertility still have only a 25 percent chance of getting pregnant after one month of unprotected intercourse (1). After one year of trying, they have an 85 percent chance of succeeding (2). We say that if a couple still isn’t pregnant after one, perhaps two, years of trying, they are infertile. It may be that they are one of the 15 percent who are fertile, but not lucky enough to conceive right away.

Dr. Polly Marchbanks, a researcher at the Centers for Disease Control in Atlanta, has poked some holes in how we define infertility. She has pointed to several studies that showed couples, when given a little time, can still get pregnant without medical help. One group of 1800 couples were considered infertile because they still weren’t pregnant after one year of unprotected intercourse. Eighty-four percent of them, however, did eventually conceive, although it took up to 10 years in some cases (3).

Still, statistics are not carved in stone. How long it takes for a couple to conceive depends on how often they have intercourse, their age and health, and whether they time conception. Some experts suggest that a couple needs to have sex three to six times per week
to maximize conception. Older couples, say infertility researchers, aren’t as sexually active as younger people so have a naturally harder time conceiving. Men and women over 40 also experience infertility for more untraceable reasons than younger couples.

Waiting for Baby

As many couples delay marriage and pregnancy, they are left with fewer years to conceive. In many cases these years are also less fertile. While women have been blamed for the higher infertility rates, both sexes are affected to some degree. Living in our world is not easy. We are faced with an increasing load of stress, pollutants, refined and processed foods, and sedentary jobs.

All of these factors plus the accumulative effect of disease and an aging body compromise health and fertility. It’s important to remember that reproductive organs don’t live in a vacuum. They must operate and cooperate with other parts of the body. If the reproductive system or some other part of the body isn’t working right, then fertility suffers. In recognizing the wear and tear our bodies go through with age, some fertility experts suggest that couples over 30 seek help if they still aren’t pregnant after six months without birth control.

Even though men are as susceptible to stress and unhealthy eating as females, women have been assigned the task of watching the biological clock. Unlike sperm, which are constantly being replenished, a female is born with all the eggs she will use in her lifetime. It is thus assumed that these eggs must lose some of their vitality with time.

Recent research has confirmed that a woman’s eggs are responsible for her decreasing fertility (4). Scientists at the University of California in Los Angeles went as far as to transplant fertilized eggs from young donors into menopausal women. The end
result was that nine out of the 14 older recipients became pregnant (5).

We’ve always assumed that because a woman’s eggs are as old as she is, they must lose their fertility with age. But is there more to this picture that we can’t see? Although a woman carries the same egg supply with her for life, these ova do not mature until the month they are released or discarded. Does this make a difference? Is it the egg that matures anew each month that dampens fertility or the body that supports reproduction?

As a woman ages, unrecognized miscarriages become more frequent. It is very difficult to study this reproductive loss. However, some researchers have used a peculiar phenomenon called the “vanishing twin” to investigate this fairly common event. One-fifth (some researchers have claimed up to 78 percent) of all women who have conceived twins end up delivering only one baby. Where does that second baby go? One explanation is the mother miscarries one of the twins and doesn’t know it, thus the term “vanishing twin” (6). Unrecognized miscarriages of single fetuses are probably just as common.

There are other reproductive changes that adversely affect a woman’s fertility the older she gets. Estrogen, needed to promote menstruation and maintain pregnancy, begins to decrease as early as 35 years old of age. Older women have less fertile cervical mucus, required to support sperm waiting for or traveling to an egg (7). Less fertile mucus means a woman is less fertile.

Fertility Signs

While a man is fertile every day of the month, a woman can conceive about one-third or less of the time. The average egg, once it escapes from the ovary, only lives for 12 to 24 hours. Sperm can survive for up to five days when they are protected by fertile mucus. But if they enter the vagina during a woman’s infertile time, they are dead within four hours and as soon as half an hour.

Fertility awareness, a system that records daily changes in a woman’s basal body temperature, cervical mucus, and the position and quality of the cervix, is one way to increase your chance of getting pregnant. Tribal women have been aware of the cyclical nature of fertility and have used it to avoid or achieve pregnancy for centuries. However, it has only been in the last 150 years or so that science has taken an interest in these fertility signs and made them accessible to modern day women.

Not all of the research done on fertility has been helpful. The rhythm method, a mathematical equation developed in the 1930s to calculate fertility, mistakenly assumed that all women have regular cycles all of the time. Menstrual cycles not only vary from woman to woman, but each woman may have cycles of different lengths from month to month–and be perfectly normal. The erroneous logic of the rhythm method has not only resulted in many pregnancies (when used as birth control), but has smeared the reputation of worthwhile fertility awareness methods.

There are several effective fertility awareness systems that will steer you toward the most ideal time to conceive. Three main fertility signs are used in part or totally by these fertility methods. Basal body temperature or BBT, probably the most familiar fertility sign, is the lowest body temperature taken during the day. It identifies ovulation and even pregnancy. When progesterone increases, after ovulation, a woman’s temperature rises. Her temperature remains elevated until menstruation and then drops. If she’s pregnant, her BBT will remain high for at least 17 days.

Using only BBT to track fertility has its drawbacks. Illness, interrupted sleep, an erratic schedule, or drinking alcohol or eating late at night can give skewed results. It’s also important to take your temperature immediately before rising. If this isn’t done,
your BBT reading can’t be used for that day. Sometimes BBT doesn’t rise during a woman’s menstrual cycle. Other times, her temperature may increase after ovulation. Obviously in these cases, BBT is no help to couples trying to conceive.

If you decide to use BBT as part of your fertility awareness program, supplement its use with other fertility signs. Use it to confirm ovulation, but don’t rely on temperature to gauge your most fertile phase.

A woman’s cervical mucus, mandatory for fertilization, is the most important fertility sign. When mucus is absent, or pasty, crumbly or has a dry infertile quality, then sperm are unable to survive long enough to reach and fertilize the egg. The naturally acidic nature of the vagina kills sperm (and protects the vagina from infections.) The disorganized consistency of infertile mucus also blocks sperm from traveling toward the waiting egg.

When cervical mucus is wet, slippery, creamy and stretchy it is fertile and will nourish and protect sperm for up to five days. In fact, the slippery quality of fertile mucus provides channels that guide sperm toward the uterus and into the fallopian tubes. If you have intercourse before ovulating, sperm hideout in small indented crypts inside the cervix. These sperm are protected by fertile mucus until ovulation occurs. Even the sweet smell of fertile mucus tells a woman that a special sugar food called glucose is mixed in with her mucus so that her partner’s sperm will be well fed until fertilization.

How the cervix sits inside the vagina also plays a role in fertility. During infertile times, the cervix positions itself high in the vagina, its opening is narrow and the cervix feels hard and unreceptive. As the fertile phase approaches, the cervix lowers itself into the vaginal canal, softens and opens its os inviting sperm to enter.

Fertility awareness obviously helps older women trying to get pregnant. This system is also useful during other times when women are less fertile. If you stop using the pill to become pregnant, you are moving from a state of infertility to fertility. Because the pill alters your hormonal balance and affects cervical mucus, your body can take months or years before it’s completely fertile again. Fertility signs allow you to monitor this process.

Modern Living

While modern life has furnished most of us with enough food to eat, a warm, secure home to live in and a job that we work at year round, these advantages can interfere with reproduction. Living in the city where light from street lamps or store fronts infiltrates your bedroom while you sleep is one problem.

There is evidence that if a woman’s bedroom is penetrated by light during her nightly sleep, her menstrual cycle and perhaps fertility may be disrupted. Anne, who had been trying to get pregnant for almost a decade, put up heavy curtains in her bedroom after she learned about this connection. Although she was making many other lifestyle changes at the same time, she finally became pregnant after years of frustration.

Fertility also varies with the seasons. Breeders know that animals procreate during certain times of the year. Unlike animals, people are sexually active and able to conceive anytime. However, there is evidence that both the human sperm (8) and egg (9) are more receptive to fertilization during particular times of the year. Sperm count, density and volume increase between February and May. In women, the quality of her egg or uterine lining is highest from October to March, peaking in November.

Certainly there are situations where timing conception is not enough to correct an infertility problem. However, learning the ins and outs of your reproductive rhythm can eliminate the need for conception roulette. No longer will you feel the need to have sex every day of the month to produce a baby.


  1. Menning, Barbara Eck. Infertility: A guide for the childless couple. Englewood Cliffs: Prentice-Hall, Inc., 1977.

  2. Trussell J, Hatcher RA, Cates W, Stewart FH, Kost K. A guide to interpreting contraceptive efficacy studies. Obstetrics & Gynecology 1990;76(3):558-567.

  3. Anon. Defining infertility. People’s Medical Journal, May 1987.

  4. Navot D. et al. Poor oocyte quality rather than implantation failure as a cause of age-related decline in female fertility. The Lancet 1991;337:1375-77.

  5. Sauer MV, Paulson RJ, Lobo RA. Pregnancy after age 50: application of oocyte donation to women after natural menopause. The Lancet 1993;341(8841):321-23.

  6. Landy HJ, Weiner S, Corson SL, Batzer FR, Bolognese RJ. The “vanishing twin”: Ultrasonographic assessment of fetal disappearance in the first trimester. American Journal of Obstetrics and Gynecology 1986;155(1):14-19.

  7. Odeblad E et al. The mucus symptom’s length and subphases during the fertile age. International Review of Natural Family Planning 1986;X(4):303-313.

  8. Tjoa WS, Smolensky MH, Hsi BP, Steinbetzer F, Smith KD. Circannual rhythm in human sperm count revealed by serially independent
    sampling. Fertility & Sterility 1982;38(4):454-9.

  9. Paraskevaides EC, Pennington GW, Naik S. Seasonal distribution in conceptions achieved by artificial insemination by donor. British Medical Journal 1988;297:1309-10.

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Written by Lauri M. Aesoph ND

Explore Wellness in 2021