Understanding a Pregnancy Ovulation Calendar
Written by: Perry Nichols
Many women use a pregnancy ovulation calendar when trying to conceive, or as a way to keep track of their menstrual cycles. However, because ovulation isn't always highly predictable, using this method as a means of birth control isn't usually recommended. Also, women whose cycles are less than 27 days apart, longer than 35 days apart, or who are often irregular should not rely on a pregnancy ovulation calendar as a way of increasing their chances of conceiving.
Determining Fertile Days
A pregnancy ovulation calendar, also referred to as a pregnancy calendar, is meant to provide an approximate window when conception may occur with most using a typical 28 day cycle as a guideline.
The most fertile day during a woman's cycle is usually 14 days before the start of her next expected period. For women with cycles that are 28 to 32 days in length, ovulation normally will take place between the 11th and 21st days.
A shorter cycle lasting 27 to 28 days will generally see ovulation occurring closer to the 11th day, while with longer cycles, ovulation will likely happen toward the end of that fertile window.
Other ways of predicting when the most fertile days are in conjunction with the pregnancy ovulation calendar are noting changes in vaginal mucous, using an ovulation predictor kit that measures hormonal changes in urine, and keeping track of basal body temperature.
Using the Calendar
To make your own pregnancy ovulation calendar, start with a blank, monthly calendar, and then note the first day of your menstrual period. It's best to take an average over a several month period, at least four to six months, to best determine the most fertile times.
Count out the average number of days during the shortest cycle and subtract 18. Use the remaining number to then start counting ahead on the first day of the next period, the day you arrive at will indicate the first day you're most likely to be fertile.
Next, subtract 11 from the number of days of the longest menstrual cycle, again use the difference to count ahead starting with the first day of the next period to calculate the approximate last fertile day of your cycle.
Understanding the Ovulation Cycle
Days 1 - 4
The first day of a cycle is when menstrual bleeding begins. The uterus now sheds unneeded tissue and blood from the previous months, preparing itself for the next month's potential fertilization of an egg. Both estrogen and progesterone levels are both at very low levels during this time.
Days 5 - 8
Days 5 through 8 are when the menstrual period ends and the endometrial lining within the uterus starts to increase due to rising estrogen levels. Basal body temperature remains low as one of the ovaries prepares an egg to be released within a sac known as a follicle.
Days 9 - 12
During days 9 through 12, the lining of the uterus thickens with extra tissue and blood in order to nourish any potential fertilized eggs. Estrogen levels continue to rise as the body prepares to release an egg. Since sperm are able to live within the body for as long as five days, having sexual intercourse during these days allows the sperm to already be present within the fallopian tubes just before ovulation occurs. The female egg, by contrast, only survives for 24 hours after release.
Days 13 - 16
During this time, estrogen production increases before dramatically leveling off, which in turn triggers a surge of luteinizing hormone (LH) from the pituitary gland. LH causes the sac containing the mature egg to burst, sending the egg into the fallopian tube to await fertilization. Ovulation has now occurred.
