Answer: First, the adult party could be subject to serious criminal penalties. There are many possible charges, depending on the facts of the case. But the adult could be facing anywhere from nine months in jail up to 60 years in prison, depending on the situation. Since the fact of the pregnancy provides very solid evidence that sexual intercourse took place, and since consent is not likely a defense to a charge involving a minor, these cases can be very difficult to defend from a legal standpoint.
However, it is also true that in cases where the relationship is a voluntary one and the two individuals are fairly close in age, prosecutors are able to exercise some discretion. Not every case of pregnancy results in criminal charges being filed or in a criminal conviction.
In addition to the possible criminal penalties the adult may be facing, the minor could be required to participate in court-supervised services and the father of the child will likely be ordered to provide support for the child.