When do women have the highest chances of getting pregnant?

Posted by Dr. Yahya MS on January 17, 2020

Every month, the female reproductive system prepare to host the baby. Awareness of this cyclical process helps women understand their fertility period in the cycle and become pregnant in a shorter time. It also helps those women that are using calender method of family planning understand their “fertility window” and prevent pregnancy.

The highest chance of getting pregnant during menstrual cycle depends on the time you release an egg during the menstrual cycle. This is variable even among women who started menstruating on the same day. It is important for the woman to predict the next date of egg release in the course of her menstrual cycles.

The day you start your period is the first day of your menstrual cycle. The length of your cycle is the number of days from beginning of one menstrual cycle to the next, and egg release occurs 14 days from your next menstrual cycle. The most fertile period is within 5 days before release of egg to the day after.

Menstruation and ovulation in 28day cycle.

How to calculate the approximate date of egg release?

If a woman has a cycle length of 28 days, for example. To calculate the likely date, she will release an egg 14 days is subtracted from her cycle length (28-14=14). This woman will likely release an egg on day 14 from the first day of her menstrual cycle. Lets take another example, a woman with 35 days cycle will likely release an egg on day 21 of her menstrual cycle (35-14=21). 

How long does the egg and sperm survive?

After you released an egg, it moves into the fallopian tube. An egg can survive in the fallopian tube for about 24 hours waiting for a sperm to fertilize it. A man’s sperm can survive inside a woman’s body for about 3 days (some sperms may live up to 5 days) in the tube waiting for an egg.

You can become pregnant if you have sex from 5 days before egg release until first day after release of egg. Your chance of pregnancy is highest when live sperms are present in the fallopian tube when you release an egg.

Days with highest chance of you getting pregnant

Consider the above example of the first woman that is releasing an egg on day 14. The days she has highest chance of becoming pregnant is from day 9, 10,11, 12, 13, 14, and 15 (i.e. 5 days before release of egg, the day of egg release day 14, and a day after the egg release, day 15). As a result, the fertile window is about six days in every cycle.

Studies have shown that probability of pregnancy from unprotected intercourse during this period is:
● 4 percent five days before release of egg
● 25 to 28 percent two days preceding egg release
● 8 to 10 percent during the 24 hours after egg release
● 0 percent for the rest of the cycle.

After the egg met with the sperm and fertilization occurs. The fertilized egg takes about 5 days to enter the womb and implant if the conditions are optimum. 

After implantation beneath the lining of the womb, it takes about 6 to 8 days for blood pregnancy test to be positive. Which is about a week before missing your period. For urine pregnancy test it may take a week after the blood test is positive. At that time we may not see the pregnancy on scan.

If you are trying to become pregnant, have sexual intercourse on your fertile days, every day or every other day. If you are trying to prevent pregnancy, you need to avoid sexual intercourse within five between the day of an egg release and a day after.

Are there other ways to know when you are releasing an egg?

Apart from determining release of egg using the cycle length, as the examples above. Other methods can be used to determine when you are releasing an egg. example of these methods includes:

1. Using secretions from the womb

Abundant, clear, wet, stretchy cervical secretions occur before, during release of egg. the day of ovulation is predicted by observing changes in vaginal discharge.

The sequence of change is: menses; then secretions follows for three to four days; it changes to scant, cloudy, sticky secretions for three to five days; followed by abundant, clear, wet, stretchy secretions for the three to four days before, during, and after ovulation; and then, no secretions for 11 to 14 days, by that time the menses has resume. 

A streched cervical mucus just prior to ovulation.

The duration of these phases, just as in using the cycle length, varies by duration of the cycle and in individual women.

2. Using basal body temperature measurement

The temperature rise begins about 24 to 48 hours after egg release and persists for at least 10 days. The disadvantage of using the method of temperature elevation is that it identifies ovulation after it has already occurred. Thus signifies the end, rather than the onset, of the fertile period.

3. Use of ovulation predictor kit

These kits are available in pharmacies without prescription. Are urine based tests that you can use at home. They do not test ovulation directly, but they test the surge of the hormone (luteinizing hormone). This hormone pushes the egg to the final stage of maturation before you release the egg.

The rise in the hormone level occurs about 36 hours before the  egg release into the fallopian tube. Women begin testing their urine one or two days before the expected surge, so that the increase over baseline levels can be observed.

Ovulation predictor kit

The kit instructions must be adhered to, as different kits are standardized to different times of the day.

4. Pelvic ultrasound scan

Ultrasound scan can be used to track the growth of the egg. The follicles reach about 20 to 25mm in diameter before it rupture to release the egg. You can have sexual intercourse a day before the egg is released. The method is not commonly used for timing of sexual intercourse, given that it’s expensive.

Ultrasound showing a follicle before ovulation

Conclusion

Identifying the time with highest chance of a woman getting pregnant, requires the knowledge of  her menstrual cycle, particularly the date of ovulation. This day changes as the menstrual cycle length changes. 

This post is for educational purpose only. It is not meant to replace professional medical advice. Please visit your doctor for proper evaluation and management.
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