Without knowing what this controls for, it doesn’t really tell you much about the cause. Does this take age into account? Does it take into account that women undergoing IVF and other fertility treatments also sometimes get other treatments to prevent miscarriages or might have genetic problems that contributed to their infertility? There are some practices, however, which I can see contributing to this. In particular, ICSI forces a sperm into an egg which could bypass natural protections against birth defects. Does this differentiate ICSI vs. normal IVF?
What bothers me is the whole thing is UNnatural.