Because in an ideal world I would make good money as a sexual health educator. But I live in Texas and George W. is president.

Alright, here are some lovely factoids about vaginas and semen - that's right, vaginas and semen! I am going to be throwing the phrase cervical mucus around, so you should start bracing yourself right now if that phrase makes you shudder. This is partly inspired by a fabulous website I found, mymonthlycycles.com, which helps users track their cycle, and will send you reminder emails when you are fertile, ovulating, or about to start your period (male readers, I apologize for use of the possessive "your").

* A woman usually ovulates 14 days before her next period. This means that if a woman has a 30 day cycle, she would ovulate on day 16.
* The normal vaginal pH is 3.8 to 4.5, the pH of semen is 7.2 to 8.0, and spermatozoa are immotile at a pH below 6. When a woman is fertile, her cervical mucus has a pH between 7.0 and 8.5, which is the optimum pH value for sperm migration and survival (according to the World Health Organization manual for examination of human semen and sperm-cervical mucus interaction 4th edition 2000). Below pH levels of 6.9, sperm die at a rate that increases with lowering pH.
*Sperm can live in the vagina 3-5 days on average under fertile conditions. During non-fertile conditions, sperm die in 2-4 hours.
* An egg lives 12-24 hours, and fertilization usually occurs 12-24 hours after ovulation.
* It takes about 2 hours for sperm to reach egg, but this can be as short as 2 minutes.
* It takes about 3 hours for sperm to fully penetrate egg.
* It takes an egg 3 days to travel down the Fallopian tube to the uterus. Once in the uterus, it takes another 3-4 days until implantation of the fertilized egg.
* An easy way for a woman to estimate her fertility is to use the Billings Method, a one-step reading of a woman's cervical mucus. "It is performed by the woman herself in a moment and without internal examination. Every day, she gently wipes the labia with clean, dry, white toilet paper. She looks at the paper to see if there is any mucus on it. If there is, she is likely to be fertile. If the mucus is wet and slippery, and can be easily stretched, then she is very fertile. If the paper stays dry, she is likely to be infertile that day. On the day of the most wet, slippery, clear mucus she is most fertile of all. This day is called the peak day, and is the very day she ovulates (Billings, 1978). She will also feel wettest on this day. She remains fertile for three days after the peak."