Ishaq bin Bakr bin Madr إسحاق بن بكر بن مضر · The Book of Menstruation and Istihadah

"That is not menstruation, rather it is a kick in the womb, so let her work out the length of the menses that she used to have, and stop praying (for that period of time), then after that let her perform Ghusl for every for every prayer."