What statistics does Hilary Erickson share about the effectiveness of exercise in preventing birth trauma?

I'm sorry for any confusion, but in the information provided, I didn't share any specific statistics about the effectiveness of exercise in preventing birth trauma. My focus was more on understanding the birth process, effective communication with healthcare providers, and setting realistic expectations to minimize the risk of birth trauma. However, exercise can certainly be a part of a healthy pregnancy and preparation for birth. It's always best to consult with your healthcare provider about the right type and amount of exercise for you during pregnancy. Is there anything else you'd like to know about preparing for birth?