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Most of us, even the ones that have been pregnant, probably have a sketchy idea of our fertile days and what exactly happens to us biologically when we do get pregnant. Here is a quick review of the biology of conception and hot to calculate your fertile days

The first thing you are always asked when you’re trying to find out about your fertile days is how long your menstrual cycle is. It’s not a trick question, but there are as many women that know the exact answer, as there are ones that are close to clueless.

Cycles are calculated from the first day of your period to the day before your period starts. Most women have cycles between 21-35 days long. Your period starts with a clear flow of blood, not spotting.

What actually happens

When you ovulate your mature egg burst from the follicle and moves down the fallopian tube. There is now a 24 hour window when the egg can be fertilised by sperm.

A man ejaculates about 500 miljon sperm during intercourse and the sperm swim the 6-7 inches through the uterus and up the fallopian tubes to fertilise the egg. This can take everything from 30 minutes for quick swimmers to a couple of days for lazy ones. Sperm are fairly hardy and can survive in the uterus and fallopian tubes for several days. So having sex around that time is more important than just trying to detect the exact day.

It is also the sperm that will define the sex of the foetus. Eggs only carry the X chromosome, sperm carry either X or Y. Sounds very scientific but it’s simple. A combination of XX makes a girl, XY makes a boy.

When the head of a sperm manages to enter the egg, it looses it’s tail and after a few hours egg and sperm melt into one entity that soon divides into two cells. It keeps dividing it’s cells every 12-15 hrs. The egg stays in the fallopian tubes for about three days and then starts moving towards the uterus.

In the uterus the egg sticks to the lining and settles, it has been about eight days since conception. The lining has become thick and spongy to receive the egg. An unfertilised egg will still attach itself to your uterus lining, but will be expelled with it and thereby start your period. An ectopic pregnancy is when the egg has settled outside the uterus, usually in the fallopian tubes. It is very painful, can cause major tissue damage and needs to be treated as an emergency.

How to check your fertility

Monitoring your cervical mucous

Cervical fluids are continuously changing and using this method you need to recognise when your body is getting ready to ovulate and facilitate the way for sperm.
The fluids to check are in your vagina, either with your finger or some toilet paper.
During ovulation your fluids will look clearer and be more slippery, like egg white. It will be stickier and gluey. You will be able to stretch it between your fingers or two papers. At other times your fluids could be more creamy or pasty. The stretchy and gluey consistency of the ovulation time is important.

Charting your morning temperature

Take your temperature at the same time every morning, starting from the first day after your period, your cycles first day. This method works best for women with regular cycles. This is a system that needs to be chartered over a few menstrual cycles to see a pattern.
When your body starts ovulating your temperature will rise by 0,5-1,6 degrees or more and will only go down when your period starts. Things like alcohol and illness can affect your temperature. The three days before the temperature rise are your fertile days/The next three days are your fertile days. If you’re pregnant your temperature won’t go down when your expected period is due. The thermometer you use should show two decimal spaces, not the usual one.

Ovulation prediction tests

Ovulation tests check for an increase in the level of the lutenizing hormone (LH) in your urine. The high LH levels indicate that your body is ready to ovulate and will release a fertile egg within 24-48 hours. The LH levels rise about 12-36 hours before you ovulate. The surge of the hormones begin in the morning and you are more likely to detect it by testing in the afternoon or evening. There are some ovulation predictions tests that test in saliva or the cervical mucous, usually very pricey.