Can you predict the baby's sex using the lunar calendar?

Pouvez-vous prédire le sexe du bébé à l'aide du calendrier lunaire ?

You're pregnant and can't wait to find out the sex of your baby? There's no need to wait for the 3rd-month ultrasound to find out whether you'll have a baby boy or a baby girl, as there are many ancestral methods for predicting your baby's sex... Among them: the lunar calendar. But is it a reliable method? We explain!

Predicting the sex of your unborn child using the lunar calendar

In the days when the lunar calendar made its appearance 700 years ago, there were no medical methods available for predicting the sex of babies. One of the techniques used at the time was theobservation of the stars, in particular the moon.

This calendar is based on two factors that would predict the sex of the baby at the moment of ovulation. These two factors are :

  • The phases of the moon, i.e. waxing or waning;
  • and the mother's age at conception.

The moon calendar is thus represented in the form of a table with two axes: one for the 12 months of the year and the other for the woman's age. To find out the baby's sex, you'd have to cross-reference the coordinates of the two axes in the table. Warning: this method cannot predict the birth of twins of opposite sexes.

Another reason why the lunar calendar is used to determine a baby's sex is that there is still a belief that the menstrual cycle is controlled by the moon's movements or cycle. In fact, the average menstrual cycle lasts 28 days, roughly the same as the lunar cycle. Menstruation therefore corresponds to the new moon. It's also believed that women's ability to conceive a child is higher on full moons and the days preceding them.

Boy or girl, is the lunar calendar 100% reliable?

Some women still use this method today to determine the month in which they wish to become pregnant, depending on whether they prefer to have a boy or a girl.

However, no scientific study has validated this method of predicting a baby's sex. In fact, the probability of the predictions being true is one in two, so it's pretty easy to believe them.

According to science, it's not possible to predict a baby's sex, since it depends on the chromosome contained in the sperm. Two XX chromosomes make a girl, and X and Y chromosomes make a boy. However, there's nothing to stop you from testing for yourself and seeing if the prediction you've made is right!

How to have a male baby according to the Moon?

According to beliefs and the lunar calendar, it's during the waning moon phase that you can have a boy. Conception must occur between the full moon and the new moon, i.e. when the first or last quarter of the moon is visible.

The other phases of the waning moon are the waning gibbous moon, the last crescent, the last quarter and the new moon.

How to have a female baby according to the Moon?

Conversely, if you wish to have a girl, it's advisable to conceive during the ascending moon phase. The ascending moon phase is made up of several periods:

  • The first crescent moon ;
  • First quarter (when the moon is in a semicircle);
  • The waxing gibbous moon;
  • Full moon.

The FAQ of the lunar calendar and the baby's sex

How can I tell if it's a boy?

There are several other ways to determine the sex of your baby. If the mother's belly is rather pointed and high, we'd tend to say it's a boy. If the pregnant woman doesn't feel nauseous, this again would indicate that it's a boy. If your cravings during pregnancy are rather salty, then it could be a boy.

How do I know if it's a girl?

As with determining if it's a boy, there are other methods for determining if it's a girl. Some say that if the pregnant woman's belly is rounded and low, it's a girl. If you're prone to nausea and sweet cravings, you could be pregnant with a girl!

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The information contained in the articles on is general information only. Although reviewed by health professionals, this information is not error-free, does not constitute health advice or consultation, and is not intended to provide a diagnosis or suggest a course of treatment. Under no circumstances may this information be used as a substitute for medical advice or consultation with a healthcare professional. If you have any questions, please consult your doctor.