The idea that you need a pillow after sleeping with a girl has no scientific basis, the sex of the fetus is related to the chromosomes and can not be manipulated by a pillow. The human sex is determined by the chromosomes, and can not be changed by any man-made way, in the sperm and egg combined to form a fertilized egg has been decided on the sex of the fetus, and whether or not you need to put a pillow after intercourse has nothing to do with, and there is no such thing as wanting to give birth to a girl need to put a pillow on the end of the same bed, no scientific basis. Human chromosomes total 23 pairs, including 22 pairs of autosomes and 1 pair of sex chromosomes, from the physiological point of view, men have XY chromosomes, women have XX chromosomes, sex chromosomes are the chromosomes that determine the sex of human beings. The sex chromosomes are the chromosomes that determine the sex of human beings. Scientific preparation for pregnancy, the birth of a boy or girl is a natural decision, do not need to be overly obsessed.