In the course of a menstrual cycle, a woman is more likely to get pregnant on some days while less so on others.
The days when women are most likely to get pregnant are known as the “fertile window”. The fertile window is estimated to last around 6 days and occurs somewhere in the middle of the menstrual cycle.
However, research shows that this is highly inaccurate and that women’s “fertile window” is changeable, unpredictable, and different for every woman. But the real question is can the fertility window fall on the days when you have your period?
In this article, we explain what research has to say on this.
About the Fertile Window
During the average menstrual cycle (28 days), there are approximately 6 days when sex is likely to result in pregnancy.
These days are estimated to be five days before ovulation and the day of ovulation itself. The reason for this is that sperm can survive in the woman’s reproductive tract for up to five days.
On the other hand, the egg can survive from 12 to 24 hours after being released from the ovary so for conception to occur, the sperm must reach the egg in this time frame. As we can see, the fertile window is highly dependent on ovulation time and the survival time of both sperm and egg.
A lot of women trying to conceive as well as those trying to avoid pregnancy want to know where in their cycle is the fertility window.
Studies on Female Fertility
Although the menstrual cycle is different for each woman, most clinical guidelines identify fertile days to be between days 10 and 17 of the menstrual cycle.
However, a study published in the British Medical Journal (BMJ) that examined conception timing in 213 women found that in only 30% of women is the fertile window within these proposed days.
According to their findings, most women reach their fertile window much earlier or later in their menstrual cycle.
Furthermore, they found that ovulation occurred as early as the 8th day and as late as the 60th day of the menstrual cycle which means that relying on the calendar is not a good way to predict ovulation.
Of the 213 women from the BMJ study, only 2% of the women were in their fertile window on the second day of their menstrual cycle while 17% were fertile on the 7th day of their cycle.
Half of the women were at the peak of their fertile window on days 12 and 13. What this means is that the chances of getting pregnant on the first days of your period are as low as 2% and the chances grow with each new day.
The study also found that the length of a women’s cycle could predict if ovulation occurred early or later in the cycle. So if your cycle is shorter than the average of 28 days, chances are your ovulation occurs shortly after your period is over.
Predicting the Fertility Window
Women can predict the time of ovulation through various methods such as using an ovulation predictor kit, monitoring the changes in the vaginal discharge, and recording basal body temperature.
However, most women aren’t that good at predicting their ovulation as seen in one study published in Current Medical Research and Opinion.
In this study, only 12% of women trying to conceive correctly estimated their ovulation day. But women could probably get the hang of it by learning more about their body and carefully monitoring the changes taking place during different stages of the menstrual cycle.
Other Things to Consider
According to one study that was published in the journal Epidemiology, cycles lasting around 30 to 31 days were most likely to result in conception.
On the other hand, shorter and longer cycles were associated with lower fertility and a greater likelihood of spontaneous abortion. The study found that menstrual bleeding of more than 5 days was also associated with greater fertility.
A probable reason for this may be that abnormal menstrual cycles are often a result of endocrine and other disorders that may affect fertility.
Although most women won’t get pregnant if having sex during the first few days of their menstrual cycle, i.e. during their period, there still is a very small chance.
However, this is highly unlikely to happen. Nevertheless, medical experts advise women and couples to not rely on the rhythm method when trying to avoid getting pregnant as 13 out of 100 women practicing the rhythm method get pregnant according to the Mayo Clinic.
On the other hand, couples trying to get pregnant are usually advised to have sex 2 times a week for successful conception as predicting ovulation is a bit tricky.
Read Alos: Can Uterus Really Grow During Menstruation?