使用“体外排精”避孕法。 使用日历法。 利用生理指标追踪排卵日期。 了解用自然方法避孕仍有怀孕的可能。

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" 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...