Fertility and Ovulation

When trying to get pregnant, timing is of the essence, because women are only fertile for a brief period every cycle, with peak fertility occurring right before ovulation. A woman’s egg lives for only six to twenty-four hours after ovulation. Using frozen sperm makes timing insemination crucial; while fresh sperm can live for five days (or more) within a woman’s body, thawed frozen sperm may only live for twenty-four hours at most.

In order to determine when ovulation is most likely to take place, you’ll need to become familiar with your own menstrual cycle—every woman’s cycle has individual variations. If possible, try to chart your cycles for at least three months before beginning insemination in order to get a sense of the normal range of your fertile days. By charting and observing the following basic tips, you should be able to identify the forty-eight-hour period during which insemination will be most likely to result in conception.  

  • The first day of your period is the first day of your cycle.
  • The last day of your cycle is the day before the first day of your next period.
  • The number of days that that pass between day one and day one is the length of your cycle.  Menstrual cycles can range between 24 and 35 days in length.
    • If your cycle starts on January 1 and your next cycle starts on January 29 then the length of your cycle is 28 days.
    • The length of you period is not the same thing as the length of your cycle
  • Ovulation occurs mid-way through the cycle, 12 to 16 days before the first day of the next cycle (not necessarily 12-16 after the 1st day of you cycle).
  • Fertile cervical mucus is one of the most useful outward fertility signs. Fertile cervical mucus is clear and slippery, resembling egg white in appearance and consistency. Women can have a range of one to four days of fertile mucus. Fertile mucus can decrease with age, and a lack of abundant mucus is one of the primary reasons for doing intrauterine inseminations (IUI), rather than vaginal inseminations.
  • If you are inseminating vaginally, you must have fertile mucus present, as the mucus provides a nutrient-rich medium within which sperm travels up into your uterus.
  • Some women also find it helpful to chart their Basal Body Temperature (BBT), the body’s base line temperature at rest, which—in many women—is lower before ovulation and higher after ovulation. BBT charting is usually only effective if you are getting the same amount of sleep every night and taking your temperature at the same time every morning, so many women find it difficult to get consistent, useful information this way. PLEASE NOTE: BBT is a good way to confirm ovulation and not necessarily the best way to predict ovulation. When inseminating with frozen sperm you need to be able to predict your ovulation.
     
  • Ovulation Predictor Kits (OPKs) are valuable tools for timing insemination; these over-the-counter kits are simple urine tests that measure the presence of Luteinizing Hormone (LH) in your blood. LH is the catalyst for ovulation, and an OPK detects the surge of LH. The LH surge indicates ovulation will occur at some point within the next twelve to forty-eight hours. The window is large because it is different for every woman. Some women ovulate the same day as the LH surge and some women ovulate two days after the surge. The OPK helps YOU determine where your ovulation cycle falls. We encourage you to test at least twice a day during your most fertile period (eg: 7am and 7pm) and to inseminate no more than twenty-four hours after getting your first positive response on your OPK.
     
  • Because you can’t predict exactly when ovulation is taking place, it’s a good idea to inseminate two days in a row, twelve-hours or twenty-four hours apart. This way you increase your chance of having live sperm waiting in the fallopian tube as the egg begins traveling down the tube after ovulation. When you get a positive response from your OPK, inseminate once that evening and then again twelve to twenty four hours later. If you’re doing only one insemination or an IUI, take your other signs (such as fertile mucus) into consideration in deciding whether to inseminate the night of your positive OPK result or the following day.
  • Once you have ovulated, it is too late to inseminate. You can determine that you have ovulated because your BBT will most likely go up and your fertile mucus will disappear and your cervic/os will close.
  • Doctors do not learn fertility awareness in medical school, and most general information about insemination is based on the characteristics of fresh sperm, not frozen sperm. If you work with a doctor, make sure that he or she is well versed in fertility and knows that frozen sperm will not live as long as fresh sperm.

For more information on how to chart your fertility, we highly recommend Toni Weschler's Taking Charge of Your Fertility, published by HarperCollins.