10.3: Pregnancy
Pregnancy is the term used to describe the period in which a fetus develops inside a womb or uterus. Pregnancy usually lasts about 40 weeks, or just over 9 months, as measured from the last menstrual period. Health care providers refer to three segments of pregnancy, called trimesters.
Pregnancy begins when a males sperm fertilizes a females egg. When fertilization occurs it is called conception. On average, females release one egg each month, which is called ovulation. Thus, for pregnancy to occur, sperm only has a few days each month where it can meet the egg and attempt to fertilize it. It is important to understand a females menstrual cycle to understand the days where pregnancy is most likely to occur.
It is very important to note that many women have irregular cycle lengths, might ovulate more then once in a month, and might ovulate more than one egg at a time, thus the fertility cycle is not an exact science.
The following description of the fertility cycle is for an average cycle of 28 days.
- Day 1: The first day of menstruation, or period. Periods typically last between 2-7 days.
- Days 1-7: Menstruation
- Sperm can remain alive and viable in the females body up to 5 days after sexual intercourse. So, it’s possible to have intercourse up to 5 days before ovulation and get pregnant as a result.
- Days 12-16: The egg is typically released, called Ovulation, around day 14 of the cycle, however it is best to estimate the release between days 12-16.
- Days 12-17: Once an egg is released from the ovaries, its life span is very short. Conception can only occur if the egg is fertilized 12 to 24 hours after the time of actual ovulation.
These biologic realities mean the actual period of viable fertility can last anywhere from 5 to 8 days. In general, you’re most fertile during the following times:
- the 5 days before ovulation
- the day of ovulation
- within 12 to 24 hours after ovulation