Whether the first sex will be pregnant or not, mainly depends on the sex is in which stage of the menstrual period, if in the menstrual period just clean time, there is still a period of time from the ovulation, so will not be pregnant; if it is in the menstrual period before, such as 3 days or 2 days of coitus, also may not be pregnant, this time the egg has already died. However, if you have intercourse within the ovulation period, you may get pregnant, because if you have intercourse within the ovulation period, the sperm and the egg can easily combine to form a fertilized egg, and the fertilized egg is pregnant when it gets into the uterine cavity and then deposits.