If your wife is pregnant, it might be a self-correcting problem, as the
estrogen produced by the pregnancy should thicken the
lining. There are various foods said to help the lining, and also acupuncture is said to be able to increase the blood flow to the uterus (but find an acupuncturist who specializes in fertility issues if you go that route). The foods are: turkey, eggs, whole milk, walnuts, Brazil nuts, pineapple core. No caffeine.