Thirty-five-year-old Esther Martin of Harrisburg, Pennsylvania, was born with Shone’s anomaly, the constellation of left-heart defects that include aortic and mitral stenosis and coarctation of the aorta. By age 10, she had had four repairs, followed by aortic valve replacement as an adult along with pacemaker implantation for heart block. So when newlywed Martin and her husband wanted to start a family, the decision was anything but casual. “I’ve always wanted to have kids but wasn’t really sure it would be possible,” she says.

Martin’s uncertainty was amplified when a regularly scheduled follow-up only a few months before her wedding—revealed a severely regurgitant mitral valve. That unexpected twist sent the couple to the altar months earlier than planned.

Within a few weeks of her wedding, Martin was at Johns Hopkins undergoing mitral valve replacement by cardiac surgery director Duke Cameron. Mere weeks post-surgery, she was talking baby with pediatric cardiologist Jane Crosson, director of the adult congenital heart disease program at Johns Hopkins.

Martin is among the growing number of women born with cardiac defects who attempt pregnancy and successfully carry to term—a testament to parallel successes in pediatric and adult cardiology, cardiac surgery, diagnostic imaging and maternal-fetal medicine. Even so, pregnancy in such patients is always deemed high risk.

Because congenital heart defects are spectrum disorders and because no two pregnancies are alike, the need for a tailored approach is that much more vital in women with heart defects. “Most can have successful pregnancies provided they have careful preconception counseling and assessment, their condition is well controlled, they are in good overall health and followed carefully,” Crosson says. Pulmonary hypertension, she adds, including cases due to Eisenmenger syndrome, is the only condition that definitively rules out pregnancy because it carries risk of complications—chiefly heart failure and death—as high as 50 percent and up for the mother.

Martin’s case illustrates the complexities. For starters, Martin’s artificial aortic and mitral valves require lifelong anticoagulation, a challenge during pregnancy given the teratogenic potential of some blood thinners and the possibility for placental hemorrhage inherent in all anticoagulation treatment, Crosson says. Even though warfarin offers optimal protection for patients with artificial valves, it can have devastating effects on the fetus, so during her first trimester, Martin received injections with enoxaparin, a type of low-molecular-weight heparin that doesn’t cross the placenta. During the second trimester, she switched back to warfarin and then to regular heparin at week 35.

To ensure that the heart is coping with the substantially higher cardiac output of pregnancy, exercise stress testing is essential, Crosson says, yet Martin’s pacemaker would have rendered such testing less useful. Instead, she had periodic echocardiograms.

Women with congenital heart disease have a small but real risk of giving birth to a baby with a heart defect—about 5 to 7 percent, compared with 1 percent for the general population. In September 2014, Martin gave birth to a healthy boy. She and her husband are already trying for baby number two.