Likutei Moharan, Part II 2:10/ליקוטי מוהר"ן·תנינא ב׳:י׳

110. And know! reciting the Psalm of Thanksgiving (Mizmor Le’todah) is a segulah for a woman who has a difficult labor. This is because Mem Lamed, the initial letters of Mizmor Le’todah, signify the seventy screams of a woman about to give birth.

2This psalm has KaSaCh letters. In the Atbash cipher, KaSaCh is CheSeD (kindness). Through kindness/ halakhot, the birth is made easy, as discussed above.

3And there are forty-three words in this psalm. A difficult labor is caused by the presence of an evil spirit which says, “Cut! GaM (neither) mine GaM (nor) yours” (1 Kings 3:26). It does not want [the child] to come out into the air of the world. Counteracting this are the Mem-Gimel words of this psalm, which neutralize the aforementioned GaM. This psalm is thus a segulah for a woman having a difficult labor.