Fertile days

Menstrual cycle is very specific and individual, and can range from 24 days to 37 days.
The length of the menstrual cycle may be affected by many things, including illness, stress, travel, fertility medication, and some other factors.

In most cases the duration of the menstrual cycle is 28 days. If the cycle is 28-day, the first day of bleeding should be considered as a first day of the cycle. It is important to remember for calculations.

Every month female ovaries begin to ripen several follicles, which is why days 1–14 are called the follicular phase. Each of the many follicles in the two ovaries is a pocket of tissue filled mostly with estrogens. The number of active follicles changes with each cycle, but typically only one follicle per month in a single ovary becomes dominant over the others and produces a viable egg. As the follicles ripen, estrogen levels rise.

Just before mid-cycle, the hypothalamus and pituitary gland release LH (luteinizing hormone) and FSH (follicle stimulating hormone) spikes to trigger the dominant follicle to ovulate. Estrogen levels continue to rise. Contraception should be used during this period.

Days 14–28 are termed the luteal phase, when estrogen levels begin to fall and progesterone levels rise.

Around day 14 (but it can vary) ovulation occurs: the dominant egg is released from the follicle and is drawn into the fallopian tube on its way to the uterus. This triggers a host of hormonal secretions — including estrogen — that thicken the uterine lining to support a pregnancy.

Important to remember - women are fertile for about 24–48 hours around the time of ovulation (before and after ovulation).

But how long can sperm survive in a woman? The answer is a very difficult one and depends on a large number of variables including the individual longevity of sperm, the internal metabolic capacity of sperm, the environment of the vagina (body temperature, pH levels, relative acidity), the presence of cervical mucus, the quality of cervical mucus, the ability of the sperm to get out of the vagina and into the womb, and the presence of sperm antagonists like immunity securing white-blood cells.

If consider the most ideal conditions (ideal vaginal/uterine environments, fertile eggs, strong sperm health, etc) sperm may be able to survive between six and seven days. That's about a quarter of a typical menstrual cycle - and that means an extended window of fertility before ovulation. In most cases, however, we can assume that there will be realistic factors that may decrease sperm longevity or inhibit sperm movement. First of all, the sperm needs to get out of the vagina and move into the uterus (through the cervix). If the sperm can't make that initial leg of the journey in a few hours, most will end up dead shortly thereafter. Now, if fertile-quality cervical mucus is present and abundant, and if the sperm make it to the cervix and the womb, then sperm life-span can be extended. On average, we can expect sperm to survive just a day or two, and given more optimum conditions or luckier happenstance, a handful of days more. Of course, with each passing day more and more sperm die and the odds of conceiving diminish.

If you a not planning pregnancy, better use safe contraception especially during fertile days.

Rhythm Method

This method is based on an observation that the ovulation in females takes place 2 weeks before menses. Now as we know that the menses cycles in women may not be on precise day every month, the calculation of the safe period is done on the basis of duration of 12 previous cycles. First note down the shortest and the longest cycles during the last 12 cycles.
The first fertile day will be minus 18 days from shortest cycle.
The last fertile day would be minus 11 days from the longest cycle.

This method is based upon observation of Ogino, in 1930 in Japan and Knaus, in 1933 in Austria. One should keep in mind that this method of contraception is some what crude.
Discover more about Calendar Rhythm Method in following page.

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