Pregnancy is a time when something wondrous happens to a woman: a new life develops within her. A woman is granted the honor of offering “hospitality” to a holy soul that will join the people of Israel. This soul leaves her during childbirth, and the woman's body loses the additional holiness it possessed during the nine months of pregnancy.
A woman expecting a child is granted special protection from Above so that the new life within her may develop safely[1].
Childbirth gives a woman the status of niddah, due to the flow of blood from the uterus during childbirth, and, in addition, the status of “ritual impurity following childbirth,” brought on by the very event of childbirth (the laws of “ritual impurity following childbirth” are identical to the laws of niddah)[2]. Among other reasons, “ritual impurity following childbirth” is explained by the fact that the woman's body loses an additional holy soul[3].
For most women, menstruation stops during pregnancy, and they remain ritually pure until childbirth. Some women, however, have bloody discharge, especially during the first three months of pregnancy, in which case they have the status of niddah.
A woman becomes a niddah with every birth or miscarriage. A woman in labor is considered a niddah from the moment strong contractions leading to childbirth begin, or from the moment of a bloody discharge if it occurs before the contractions.
There are a number of complex laws concerning childbirth on Shabbat and holidays. A couple expecting a child should consult a rabbi for an explanation of them, preferably as early as the beginning of the ninth month of pregnancy. In any case, a woman who feels on Shabbat that it is time to give birth should get to the hospital as quickly as possible. If the hospital is far away, she may travel by car or call an ambulance.
Bleeding after childbirth or miscarriage usually continues for several weeks. When it stops, the woman follows the usual purification process: a “hefsek taharah,” counting “seven clean days,” and immersion.
Most breastfeeding women do not menstruate. In such cases, once postpartum bleeding has stopped and the woman has immersed in a mikveh, she remains ritually pure for as long as menstruation is absent. A nursing mother who menstruates despite breastfeeding acquires the status of niddah.
[1] Midrash Rabbah on the Torah portion Tazria in the book of Leviticus, the third book of the Pentateuch. Midrash Rabbah is a commentary.
[2] Leviticus, 12: 2, 5.
[3] The author of “Shem MiShmuel” cites this explanation in the name of his grandfather, the Kotzker Rebbe, and his father, the author of “Avnei Nezer.”