Chromosome variety
The chromosomes of the sperm cells of the male determine whether the baby is a boy or a girl. The gender of the baby is determined by the chromosomes. They determine our body looks like and how it works. They are also the reason we resemble our parents. Usually, all of us having 23 pair of chromosomes. The 23 pair of chromosomes are different to males and females. The sperm cells are produced by male. The sperm cells could have either an "X" or a "Y" chromosome.
If a sperm with a "Y" chromosome fertilizes the egg, then the chromosome combination for the baby would be "XY" and the baby is a BOY. If a sperm with an "X" chromosome fertilizes the egg, then the chromosome combination for the girl would be "X" and the baby is a GIRL. Therefore, the gender of the baby is determined by the male. The male has two type of chromosomes which are "X" and "Y" but the female has only one type which is "X". Usually, babies are born healthy, but sometimes may be born with a disability.

Why some babies are disabled at birth?

Small Baby
There are so many causes of disabilities and cannot always be explained. We all know lack of oxygen at birth can cause dames to the brain. If the mother smokes or takes drug during pregnancy, it can have serious consequences because the drug reaches the blood circulation of the child via umbilical cord. Sometimes there may be genetic changes which may cause disabilities. For instance, a change in 21st chromosome, causes Down syndrome in the child. It is important to ensure that people with disabilities and are not discriminated against in our society.

How babies are born?

When a man and woman having sex, the erect penis of the male is inserted into the vagina of the female. The sperm cells of the male are ejaculated into the vagina of the female. About 300 million sperm cells are present in the woman's vagina. The sperms swim forward with the help of their tails to fertilize the egg cell within 12 to 24 hours. A single egg cell is enough to fertilize the egg cell.
A new life can start with the fusion of the sperm and the egg, which contains the genetic information of the father and the mother in equal parts. Here the egg divided into several parts in fallopian tube. It finally gets lodged in the mucous membrane of the uterus, a special hallow muscle. This has a good blood supply and provides the egg cell with nutrients. The baby develops in the woman's uterus for about 40 weeks, till it is developed to be born.