High doses of Regestrone
given 45th day onwards of conception,is known to cause masculanization in female fetus ,if In male fetus there is no effect.
Your wife has taken a very short course of registerone in December, With probable ovulation on10th of November, So,most likely tshe has consumed pills before 45th day of conception,
Still get pelvic sonography
done to confirm fetal age ,on the days of pill consumption. If it is confirmed to be less than 45 days she can continue with the pregnancy