Giving birth

This is a weird question but im starting to really stress myself out as i think about labour.... i am a size 0 extremely petite and my vaginal opening is TINY. how is this baby going to squeeze out of there???? I just can't imagine anything bigger than an apple pushing out of there let alone a baby! am i being stupid and naive? this is my first baby so I'm not sure what my body is capable of doing... also am going to have a home birth with a midwife does anyone went through the same situation??