This depends upon number of sperms which entered inside. If small number of sperms entered inside then pregnancy is not possible. Because only one sperm is needed for fertilization but normal sperm count in an ejaculate should be 40 million per ml and 2-3 ml volume is normal. This high number of sperms is needed for pregnancy because out these millions sperms in an ejaculate thousands reach in fallopian tube. Here these sperms secrete an enzyme which dissolve the shell of the egg. After this one sperm is able to enter in egg causing fertilization. So, you have poor chances of pregnancy if small number of sperms entered inside.