How does Nature decide “Girl or Boy”?

Quite often parents with a number of kids will timidly ask, „why are all four boys(girls) how nice would it be if we had had also a girl (boy)!” 
did they do something ‘wrong’?

First there are some facts, eventually these were teached in our schools Biology-class, but we just forgot about:

1.   the egg contains the genes of the mother and it always has an X-chromosome.

2.   the spermium contains the genes of the father, but there are two types of it: those who also carry an X-chromosome, and those who have an Y-chromosome instead.

3.   “X” sperms are responsible for a girl, as “Y” sperms fertilize a boy.

4.   the egg can be fertilized over a period of approximately 24 hours after ovulation.

5.   Y-sperms are moving fast but only survive few hours. X-sperms are much slower, can’t win a race, but have some longevity (few days).

In general,  nature tends to care for balances, and thus, if very frequent intercourse happens to the woman (oha! too many men!! /too few women!!) it gives precedence to babygirl pregnancy. It is, many X-sperms already wait near the ovaries for the next ovulation.

Else, if intercourse is quite rare (oha! too few men!!/ too many women!!), then those quick Y-sperms will win the race and “it becomes a babyboy”.

The clue is, to „know“ as exact as possible, when ovulation will happen. One of the means is the temperature measurement method, documented over several months

A supplementary note be dedicated to the fact, that sometimes, when ovulation is near anyway, it just happens as being triggered by the female orgasm. This of course (and only after a week of abstinence!) greatly enhances the fertilization of a boy.

The SYMPTO-THERMAL METHOD is NOT Calendar Rhythm! It was developed by leading obstetrician/ gynecologists and further refined. With this method, a woman observes two or three fertility signs which occur naturally within her monthly cycle. As the signs are observed and recorded, her fertile and infertile times are determined.

The two most commonly used signs of fertility that you need to observe are a woman's normal cervical mucus secretions and her waking temperature. A third and optional sign is the physical change that occurs in her cervix.

It takes just five minutes each morning for a woman to take her waking temperature. Then during the day she takes a moment now and then to become aware of her cervical mucus. Once the information is recorded, she has a complete and cross-checking picture of her fertility - IT'S SIMPLICITY in  ITSELF!!!

An increase of temperature by ~0,5°C will occur at ovulation. It decreases again with next menstruation.
The cervical mucus is quite thick most of the period but gets more fluid in those days of fertility around ovulation

- for more detail see:


A final and
essential remark:

This method is as well suitable to avoid pregnancy, if desired so. Essential in this realm is to know: There is no »safe« time in between mensis and ovulation.
Only after the ovulation, when temperature had been elevated for three days, conception is sufficiently improbable!