A pregnant women may refuse a blood transfusion if it conflicts with her religious beliefs, provided the decision does not endanger the life of the child she is carrying, according to the Maryland Court of Special Appeals.

The state's second highest court last week upheld a Baltimore Circuit Court ruling that prevented doctors at Mercy Hospital from giving a transfusion to a woman whose baby was to be delivered by cesarean section.

Ernestine Jackson, a Jehovah's Witness, refused a transfusion in February 1984 because of her religion, despite doctors' warnings that she could die without additional blood.

The hospital's doctors took the case to Circuit Judge Martin Greenfeld, asking that a guardian be appointed for the woman with the power to consent to a transfusion because the risk to her life was unacceptable.

But Greenfeld denied the request after a hearing at Jackson's bedside at which doctors confirmed there would be no danger to the infant. Greenfeld ruled that Jackson had the right to refuse treatment if her decision was made "knowingly and voluntarily" and would not endanger the "delivery, survival or support of the fetus."

The operation was successful without a transfusion and the mother and baby survived, but Mercy asked the appeals court to review the case so doctors would know what to do if a similar situation occurred.