Give scientific reasons : When birth time is near, two chemical signals associated and produces real parturition pain / labour pain.

Some cells of embryo start producing oxytocin. That excites to release prostaglandian of placenta. These both hormones induces consistent and powerful contraction of uterus. At this stage, signals of oxytocin are released from posterior pituitary gland.

Combined effects of increased level of oxytocin and prostaglandin promote labour pain. Due to strong contraction more oxytocin is released. As a result powerful contraction occurs. That penetrates foetus deep from abdomen. This takes out foetus from uterus immediately after that child is delivered.