Fertility refers to the ability to give life. The “fertility rate” refers to the number of children born for each person, couple, or population.
For humans, fertility depends on a number of factors – sexual behavior, culture, nutrition, timing, emotions, and more. Animal fertility is similarly complex, often with amazing mechanisms that are only now being understood.
Fertility is a term also used to describe farmlands. In this use, it describes the ability to grow large crops of fine fruits, vegetables, or seeds.
In Western cultures, the fertility rate measures the number of children per woman. It was seen to be a reliable indicator of population growth; however, that no longer applies to Asia. In China, India, and Myanmar, selective abortion and other factors have caused a decline in the number of women when compared to men. Therefore, the traditional definition of fertility rate is no longer an accurate measure for these areas.
For women, hormonal cycles determine when they may become pregnant. This cycle is 28 days long. Men also experience hormone cycles that determine when they are most fertile. While they create and ejaculate sperm at any time, occasionally the quality of sperm dips. Scientists believe this relates to their hormonal cycle.
In each 28 day menstrual cycle, women are fertile for around seven days. Once ovulation occurs (on day 14 of the fertility calendar), the woman is most likely to become pregnant. However, the egg breaks down within two days. Conception can occur in the five days before to two days after ovulation.
For women, fertility peaks in the early 20s. By age 30, fertility decreases. With the number of women who are postponing pregnancy to pursue careers, infertility has become a problem. As she ages, the risk of miscarriage likewise increases. Birth defects become more common. For many women, using fertility drugs has become a viable alternative.
Unlike women, male fertility does not decline with age. Erectile dysfunction increases with age, and the availability of drugs to combat this problem has met with great success. Even men in their 90s have fathered children. However, sperm count decreases with age, making pregnancy slightly more challenging.