It is one week since your period started, so with a 28 day cycle it is about a week before ovulation occurs. An egg (or ovum) in one of the woman's ovaries starts to ripen and mature (2 eggs if she is preparing to have twins!) During this week her body starts to prepare for possible conception and pregnancy. Oestrogen hormones increase (as does her libido) and her uterus and cervix start to produce a special fertile mucus, which fills the opening of her cervix and lines her uterus and fallopian tubes. This fertile mucuc acts as a continuous stream, transporting the man's sperm up into her fallopian tubes, in readiness for when the egg is released. The mucus is capable of protecting the man's sperm and helping it to survive in the woman's body for up to 3 to 5 days.
Image 65-21 shows the woman's reproductive system illustrating her uterus, cervix, fallopian tubes and ovaries.
The timing of sexual intercourse to coincide with the exact time of ovulation can be difficult. However, studies of human fertility show that conception is more likely to occur if a couple have sex 1 to 3 days prior to ovulation. This allows the sperm to already be 'lying in wait' in the woman's fallopian tubes. Therefore a woman's most fertile time each month is thought to be about 1 to 3 days (but up to 5 days) before she ovulates. You can read more in class A.
Image 65-04 shows a microscopic image of a single sperm.
Go to Week 2