The preferred manner of delivering the baby in a gravido-cardiac case is vaginal delivery assisted by forceps under epidural anesthesia. The main rationale for this is:

A. To allow a gradual shifting of the blood into the maternal circulation
B. To prevent perineal laceration with the expulsion of the fetal head
C. To allow atraumatic delivery of the baby
D. To make the delivery effort-free, so the mother does not need to push with contractions

For gravido-cardiac patients, vaginal delivery assisted by forceps under epidural anesthesia is preferred to allow a gradual shift of blood into maternal circulation, minimizing the effort required from the mother, which is crucial for her condition.

Explanation:

The preferred method of delivering a baby for a gravido-cardiac patient, a pregnant woman with heart disease, is via vaginal delivery assisted by forceps under epidural anesthesia. The primary rationale for this approach is to allow a gradual shifting of the blood into the maternal circulation. This method is chosen over others, like Caesarean section, which is major abdominal surgery that can lead to post-surgical complications and might not be the safest option for women with cardiac issues. Vaginal birth, especially with the assistance of forceps and under epidural anesthesia, helps in making the delivery effort-free for the mother, thus she does not need to exert herself by pushing with contractions, which can be particularly beneficial for a gravido-cardiac patient.