Fertility depends on many factors including a sufficient amount of sperm being produced and released into the vagina, passage of the sperm up into the fallopian tubes, release of an ovum into the fallopian tubes and the penetration of one or more sperm into the ovum.
For pregnancy to occur, the fertilized ovum will then need to implant into the wall of a female’s uterus. To conceive a child, a woman must ovulate. Ovulation, or ovulating, is the process during a female’s menstrual cycle whereby a mature ovum (egg) is released through the ovarian follicle (wall) and into the fallopian tubes, ready to be fertilized by a male’s sperm. Some women experience pain in the lower abdomen when ovulation occurs. This is called mittelschmerz, which means ‘middle pain’ in German, and occurs when the ovarian wall stretches as an ovum (egg) is released from the ovary.
A woman is likely to be fertile 10 to 14 days after the start of menstruation. Fertility can therefore be defined by this process working correctly, with males producing healthy sperm and female’s ovulation cycle occurring correctly.
In 1 to 2 per cent of all ovulations more than one ovum can be released. This can result in multiple births if both eggs are fertilized by sperm, resulting in non-identical twins as the DNA is different in each fertilized ovum. Identical twins can be conceived when one ovum is fertilized by a single sperm and the ovum separates in the early stages of development. The term fertility can also be used to describe the process of giving life in nature, in both plants and animals too.