Miscarriages maybe but I believe stillbirths are legally required to be recorded. As unpleasant and upsetting as it is, it would be an interesting data point in it's own regard to observe.
Unfortunately, I have lot of personal experience here. The reporting on still births varies greatly. Some states require it past week 16, others stipulate a birth weight, and others set more arbitrary criteria. You would have to account for a lot of external factors.