I found a close iteration of this segula here
"Segulos for Zera Kayama – Better Than a Segulah" https://www.betterthanasegulah.org/free-services/segulos/segulos-for-zera-kayama/
If a woman is having difficulty with child raising or she doesn’t have children altogether, it is a segulah to say the haftorah of the first day of Rosh Hashanah (“Vayehi ish echad min haRamasayim Tzofim…”) after hadlakas neiros. She should understand the words that she is saying and say it with kavannah, and she should give tzeddakah before lighting the candles. Through this she will be remembered for children who are talmidei chachamim and tzaddikim. (In Yerushalayim this is an established custom in the name of the Arizal.)
Although it doesn't mention having 40 women say it at the same time, it's pretty close.
(The Haftara for the 1st day Rosh Hashanah includes tefilas Chana)