Since these days, the Old testament Laws are more important than ever, why do you think giving birth to girls is more unclean than boys?
New International Version (NIV)
Purification After Childbirth
12 The Lord said to Moses, 2 “Say to the Israelites: ‘A woman who becomes pregnant and gives birth to a son will be ceremonially unclean for seven days, just as she is unclean during her monthly period. 3 On the eighth day the boy is to be circumcised. 4 Then the woman must wait thirty-three days to be purified from her bleeding. She must not touch anything sacred or go to the sanctuary until the days of her purification are over. 5 If she gives birth to a daughter, for two weeks the woman will be unclean, as during her period. Then she must wait sixty-six days to be purified from her bleeding.