Summarize this article in one sentence.
" One way to diminish the chances of pregnancy without using a condom is to try the withdrawal method. This method consists of the man removing his penis just prior to ejaculation, so that the sperm do not have a chance to travel up the woman's vagina in a way that may lead to pregnancy. The challenge with this method is that some sperm may leak out prematurely (prior to ejaculation and thus prior to withdrawal of the man's penis), which is what makes this method only 78% effective at preventing pregnancy. " Technically, there are only a few days each month when a woman can actually become pregnant. Most women have a 28 day cycle, which starts on the first day of her period. On average, ovulation occurs on day 14, but a woman can be fertile for several days before and after ovulating.  If a woman has sex significantly before or after her most fertile days, her chances of becoming pregnant are much lower. The downside to the calendar method is that not all women have exactly 28 day cycles. There is quite a bit of variability between women, and one woman may even find that her own menstrual cycles are not completely consistent from month to month. It is for this reason that this method is only 76% effective at preventing pregnancy, without the use of a condom. If your cycle is consistently more or less than 28 days, subtract 14 days from the END of your cycle and consider this the start of your most fertile few days. The second half of a woman's menstrual cycle (following ovulation) tends to be much more consistent than the first half of the cycle (prior to ovulation). One way to track your fertility is to use physiological markers such as basal body temperature measurements, and/or observing cervical mucus discharge, to help pinpoint the specific days when the woman's fertility peaks. You can then avoid having sex on those days when the woman's fertility is high.  With the "basal body temperature" method, a woman measures her temperature first thing in the morning and before eating every day. It will rise 0.4-1.0 degrees Fahrenheit following ovulation. Therefore, it is advisable to use a condom, a spermicide, or another non-hormonal form of birth control from the first day following the woman's period to three days after her basal body temperature has risen. With the "cervical mucus" method, the woman observes the characteristics of her cervical mucus discharge. There is typically no mucus discharge immediately following a period, mild and sticky secretions in the days after that, greatly increased mucus secretions that are more wet and clear in the days surrounding ovulation, and no noticeable secretions following the end of her "fertile period" all the way until the beginning of the woman's next menstrual cycle. Therefore, during days when cervical mucus is abundant, clear and wet, it is important to avoid sexual intercourse as this is when a woman's fertility is at its peak. Both the withdrawal method as well as the calendar method are significantly less effective than the medical methods of contraception. It is important not to rely on these techniques if you are truly seeking to avoid a pregnancy. Here's why:  If you are a man and you inadvertently get a woman pregnant, in most places she has 100% choice as to whether or not to proceed with the pregnancy (or whether to get an abortion). This may mean that, by getting a woman pregnant, if she chooses to keep the baby you are now responsible financially to help out, and may take on the responsibilities of co-parenting duties as well. Both men and women are impacted by unintended pregnancies. Having the responsibilities of supporting a baby before you are ready can significantly impact (and potentially get in the way of) other plans you may have, regarding career, relationships, or any other sphere of life. If you are the woman and you inadvertently become pregnant, you may be faced with the challenging decision of whether or not to keep the baby or to proceed with abortion, if this is legal in your area.

Summary:
Try the "withdrawal method. Use the "calendar method. Track your fertility using physiological markers. Understand that natural methods still pose a risk of pregnancy.