DALLAS, Nov. 4 -- More women with heart disease are surviving to adulthood and contemplating pregnancy, but precautions may be needed to prevent complications in both the mother and child, according to a study in today's Circulation, a journal of the American Heart Association.
Pregnancy and childbirth make the cardiovascular system work harder, which can cause serious problems for women with a history of heart disease.
"While most women with a history of heart problems can go through pregnancy without difficulties," says Samuel C. Siu, M.D., a cardiologist at the Toronto Hospital, "some patients will run into problems."
The study found five "risk factors" that place women at higher risk for complications: prior cardiac event (prior heart attack, stroke, or heart failure), prior heart rhythm abnormalities, a low rating on the New York Heart Association (NYHA) functional class or cyanosis (low oxygen levels in the blood). (NYHA is a four-point classification system used to measure physical impairment). Other factors were obstructions to blood flow in the left side of the heart and heart muscle weakness.
Having one predictor puts the mother at a 30 percent risk of pregnancy complications, the researchers report. Two predictors increase the risk to 66 percent.
"This is the first study to try to put together various predictors and create a scoring system which may be helpful to doctors trying to advise these patients," Siu says. "We are now in the process of evaluating this scoring system in a large study involving 14 medical centers across Canada."
The predictor scale could prove useful in pre-pregnancy counseling as well as in the care of pregnant women with heart disease, the researchers write. "Those at greatest risk can be appropriately managed at facilities that treat high-risk patients, while those at low risk may receive their care in the community setting."
Many of the studies currently used to advise patients were published in the 1980s.
Since then many changes have been made in the treatment of heart disease and pregnancy. For instance, congenital heart defects are now more common than problems caused by rheumatic fever, say the researchers.
In the study of 221 women and 276 pregnancies at three Toronto hospitals between 1986 and 1994, there were 24 miscarriages and 252 pregnancies that resulted in births.
Overall, maternal complications -- such as heart failure, arrhythmia (irregular heartbeat) or stroke -- occurred in 45 (18 percent) of the pregnancies. Complications were reported in 42 of the newborns. Two babies died. Respiratory distress syndrome affected 16 babies, 2 infants had intra-cranial hemorrhage (bleeding), 35 babies were premature, and 14 had low birth weight for their gestational age.
The data collected included each woman's rank on the NYHA scale at her first prenatal visit, as well as presence of high blood pressure, history of heart failure, stroke or other heart and blood vessel problems, heart medications, cyanosis, prior cardiac surgery, and other factors.
The majority of the women were in NYHA class II or I at their first visit, the mildest levels of impairment. A higher risk of miscarriage corresponded to poorer NYHA functional class and greater cyanosis. For instance, the miscarriage rate was 17 percent for women in NYHA class III -- which means they were limited in their physical activity -- compared to 2 percent for women in class II or I.
Co-authors include: Mathew Sermer, M.D.; David A. Harrison, M.D.; Elizabeth Grigoriadis, M.D.; Grace Liu, M.D.; Sheryll Sorensen, R.N.; Jeffrey F. Smallhorn, M.B., B.S.; Dan Farine, M.D.; Kofi S. Amankwah, M.D.; John C. Spears, M.D.; and Jack M. Colman, M.D.