For the loving parents doesn't matter whether the boy or the girl was born at them. And still sometimes there is desire to give birth to the child of the defined sex, for example, the son already is, there is a wish to get also the daughter.
The sex of the person is defined by the combination of special chromosomes – sexual which have two types: X and Y. The women's set of chromosomes – XX, men's – XY. Sex cells contain the haploid (half) set of chromosomes, possessing only one sexual chromosomal. In the ovum there can be only the X-chromosome, there are no others in the female body, and in the spermatozoon of either X, or Y. Thus, the sex of the child is defined by what sexual chromosome is born by that only spermatozoon which will connect to the ovum at fertilization. To conceive the girl, X-chromosome is necessary.
There are special diets promoting conception of the child of the defined sex, but their influence on the embryo on the early term when the woman doesn't know yet that she is pregnant is insufficiently studied. To use such diets risky.
In effect, process reminds the lottery, to affect the course of which very difficult. Someone will call it "God's will", someone – "the game of the blind case". And still there are certain regularities.
Spermatozoa with different sexual chromosomes differ from each other a little. Y-spermatozoa are more sensitive to the alkaline environment of the vagina. It is neutralized by the secret, allocated at the orgasm. Therefore, if the woman of the orgasm didn't test, Y-spermatozoa will have much less chances to meet the ovum: they will die, thereby "having provided chance" to H-spermatozoa. Introspection will help to avoid the orgasm. If the woman notices that most often she tests the orgasm in the morning, so it is necessary to have sex in the evening. It is necessary to explain to the husband what actions from his party lead to the orgasm and to ask it to abstain from such actions.
It is necessary to understand that all attempts to affect the sex of the child only increase the probability of conception of the girl, but don't guarantee result for 100%.
Death of "undesirable" men's cages with Y chromosome in the alkaline environment of the vagina will be especially probable, than longer there will be the way to the neck of uterus. To increase distance, sex in the pose which isn't assuming deep penetration of the penis into the vagina is necessary. It distinguishes, for example, that pose which it is accepted to call "missionary". H-spermatozoa are less mobile, than those which bear the Y-chromosome, but they live slightly longer. To use this distinction, the woman has to study very well the menstrual cycle and precisely the nobility when at it there comes the ovulation. It is possible to calculate this term by such formula: to subtract from the usual duration of the cycle 17 and to count the received number of days of the first day of the last periods. For example, the cycle usually lasts 25 days, the last monthly began on March 1, therefore, the ovulation has to begin on March 9. It is possible to use special tests for the ovulation within several months. They remind tests for pregnancy, but react to other hormones, and it is necessary to apply them not right after the dream, and between 10:00 and 20.00. Having established by means of calculations and tests in how many days after the beginning monthly at the woman there comes the ovulation, it is possible to start business. To have sex it is necessary to begin right after end monthly, and three days prior to the ovulation it is necessary either to abstain, or to use condoms. For three days the most part of Y-spermatozoa will die, and H-spermatozoa will survive, and conception of the girl will be provided.