This is not true, in this context. 75% happen within the first two weeks. No excess nutrition is required in that time. Folic acid is important, but someone having multiple miscarriages, under the care of a doctor, will obviously be taking the recommended supplements.
This sounds like the sort of giddy overfocusing we do when we project a certain lifestyle (usually one we already live, ourself) as a cure-all onto everything else including people we know nothing about.
I remember being jacked at 20 years old, eating spinach and egg whites at the university cafeteria, looking somberly around at everyone—who I'm sure didn't do 100 air-squats each day—while they devoured fried chicken strips. I felt bad for them. How many ailments could we fix if everyone did 20 push-ups when they woke up in the morning and then snorted a cup of oatmeal? Real cocksure of myself, I'd shrug and think what a shame.
What I'm trying to say is, did OP's wife try doing pull-ups while eating paleo?
There are some diets that can affect hormones/cycles, but it’s eating special foods, not laying off the ice cream.