Of all the three measure causes of sub fertility three important factors are ...

A. Late Marriage

B. Environmental pollutions and liberal use of  pesticides in the green vegetables whatever we purchase and consumes- food and bad cooking habits leading to formation of AGE (Endocrine disruptors) and thirdly

C. Husband and wife remain separated of income purpose – Intrastate or interstate migration for jobs

Many males are now employed gainfully in different district or different states or union territory of our mother land leaving behind their young wife to take care of elderly parents and possible cattle’s . in such cases it will be very essential if a women can anticipate ferial period well ahead so that husband can come at a short notice. However can be calculated from previous cycles lengths, serial cervical mucus test. LH urinary kit is only applicable where husband is employed with in 200 KM of her residence so that a railway or bus ticket are easily available  Position of calculating day of ovulation in human beings where as in animals only copulation brings out ovulation.

What do we mean by “fertile window .It is time to change: Is our existing idea on timing of ovulation is wrong?? What do we mean by “fertile window and shall we change the definition after being used for long 50-70 years.”?? Is our existing idea on timing of ovulation is inaccurate /wrong?? How is the concept that ovulation occurs from day 10-16 in normally spontaneously Ovulatory women so that timed coitus may be planned when husband is employed outside the home town or one depends on withdrawal method of contraception as method  of   Natural Family planning. The fertile window may last between 1 day and 5 days and the chance of natural pregnancy is signifi­cantly greater the longer it lasts. For example, when the fertile window is only 1 day, the fecund ability ratio is 0.11 compared with 2.4 when it lasts for 5 days. Wilcox et al. estimated that A) 2% of women were in their fertile period by day 4 of their cycle, B) 17% by day 7 and C) 54% by day 12. Most women appear to reach their fertile window early in the cycle, although a proportion does so much later, even past day 35.