The Kotzker Rav gives a wonderful explanation regarding the start of our sedra. Why does a woman becomes tamei’ah (spiritually impure) after she has given birth? He quotes the gemarra that giving birth is one of the 3 ‘keys’ which stay exclusively in the hands of HaShem and were not given to an emissiary. As a result, when a woman is on the birthing stool giving birth, she has a special kedusha accompanying her. But when the baby comes out and the birth process has ended, the ‘giving birth’ kedusah goes away. And the tumah (impurity) is there as a result of the void of the extra kedusha. This, the Kotzer Rav says, is also why there is impurity (tumah) from a dead person – because
when the neshama takes leave, it leaves behind a void of kedusha and so tumah is present.