Can I become pregnant on infertile days?

Can I become pregnant on infertile days?

One of the frequent questions asked by many patients in the gynaecology clinic is whether they can become pregnant on infertile days. We have the expert opinion of Doctor Cecilia Quetglas, Instituto Bernabeu Gynaecologist in Palma de Mallorca, who tells us the key to knowing when our fertile days are, and answers the question of whether pregnancy is possible on days considered infertile.

Firstly, we must understand how the woman’s cycle works.

A regular menstrual cycle usually lasts between 28 and 30 days, although shorter cycles of 21 to 24 days and longer cycles of up to 35 days may be normal.  

The first day of the cycle begins with the first day of the period. In this phase, our body begins to produce a series of hormones that make one of the ovules inside the ovary grow and mature. Halfway through the cycle, on day 14 of 28 day cycles, ovulation occurs. The ovule is released toward the Fallopian tube, where it remains for approximately 24 hours. Here, two things may occur:

  • the ovule is fertilised by a sperm cell and pregnancy may occur, or
  • the ovule is not fertilised, the body therefore ejecting it and menstruation (the period) occurring, another menstrual cycle beginning.

In reality, women can only become pregnant during a few days of each cycle, those called “fertile days”.

What are fertile days?

A woman’s fertile days are those which increase the likelihood of becoming pregnant, being the days close to ovulation. Maximum fertility is achieved the day before and the day of ovulation, although sperm cells are capable of surviving in the woman’s body for 72 hours, some even up to 5 days; therefore this fertility window may last up to a week.

In a 28 day cycle, the most fertile days are between the 11th and 16th day of the cycle.

Why can pregnancy also occur on “infertile” days?

There are many internal and external factors which may affect menstrual cycles, “shifting” ovulation, and therefore moving the theoretical fertile days without prior notice.

Women with regular cycles may have cycles of different durations, and cycles may change over the years. Additionally, not all women have regular cycles, therefore it may be difficult to calculate this fertility window.

For this reason, in any case of unprotected sex there is a risk of pregnancy, and it may be necessary to take a pregnancy test in case of a late or missed period.

Can I become pregnant without ovulating?

No. A natural pregnancy only occurs when the ovule is fertilised by a sperm cell. For this to happen, it is necessary for the ovule to be released from the ovary through ovulation.

One of the functions of birth control pills is to prevent ovulation, and thereby prevent pregnancy.

How to calculate infertile days?

Without using contraceptives, some women choose to observe their cycle to track their infertile days. Remember that although pregnancy is less likely on these days, it is never impossible.

In a 28 day cycle, the days of lowest fertility are those furthest from ovulation and closest to the period; that is, between the 22nd day of the cycle until the 8th day of the following cycle.

Today there are online calculators, which based on the cycles of each woman predict the days of highest and lowest fertility, and which may be of great use. You can consult the calculator that we offer you at Instituto Bernabeu.

Dr Cecilia Quetglas, gynecologist at Instituto Bernabeu

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