As an obstetrician-gynecologist, I care for pregnant women who need services ranging from routine prenatal care to treatment for high-risk pregnancies. Whatever their needs, my patients expect that I will base medical decisions on my training and experience as a physician and that I will place their health and safety above all other considerations.

Congress wants to change this. Three years ago, Congress passed the first-ever federal ban on abortion. Because the ban would harm my patients, I joined one of the three legal challenges to this law, National Abortion Federation v. Gonzales. During the past week, the Supreme Court of the United States heard arguments in two of these cases.

The law in question runs counter to everything I've learned from more than two decades of caring for pregnant women. The ban seeks to substitute the judgment of politicians for that of doctors.

The federal ban prohibits some abortions as early as 13 weeks in pregnancy. It prohibits a range of abortion methods that doctors use because they are among the best and safest for patients. The ban has no exception that would allow doctors to provide the care they believe is most medically appropriate, even when a woman's health is threatened.

This is not a political or abstract discussion for me. The patients I treat include pregnant women with serious medical conditions that threaten their pregnancies, their health, or both. Some choose to end much-wanted pregnancies after learning that they would give birth to babies with severe anomalies. Several times a year, for example, I perform abortions for women who would otherwise give birth to babies sure to die because they lack most of their brain or spinal cord.

The medical issues that lead many of my patients to end their pregnancies are often grave, and the diagnoses a devastating blow to them and their families. I frequently perform abortions for women whose "water" has broken prematurely in the second trimester of pregnancy. This condition can subject pregnant women to significant risk of infection at a time in pregnancy well before they could give birth to a living, healthy baby. The treatment — often necessary to preserve their health and ultimately their life — could violate the federal ban. Many of these patients think of their circumstances as a "miscarriage," unaware that the federal abortion ban prohibits some of the safest techniques to protect their health.

Some of my patients, after finally becoming pregnant, learn that they need an organ transplant or that they are suffering from heart disease so severe that continuing the pregnancy would not only jeopardize their current health but might worsen the underlying heart condition. Others have had brain tumors, ruptured brain aneurysms, strokes and many different types of cancer. These patients terminate their pregnancies to avoid risk to their health and to begin lifesaving therapy for themselves, often in hopes of one day becoming healthy enough to have a baby under safer circumstances.

If the Supreme Court allows the federal abortion ban to go into effect, it will jeopardize my ability to provide the safest health care to women confronting these severely troubled pregnancies. Like all physicians, I adapt my techniques as each procedure progresses to provide the safest possible care for each individual woman. This ban would interfere with my ability to do so, taking medical judgment out of my hands and putting it in the hands of politicians in Washington.

During the three legal challenges to the ban, I joined other physicians from leading teaching hospitals throughout the country who testified that this law prevents us from providing the safest medical care for our patients. The American College of Obstetricians and Gynecologists, representing more than 90 percent of all obstetricians and gynecologists in the United States, opposed the law, stating that "the intervention of legislative bodies into medical decision making is inappropriate, ill-advised, and dangerous."

To date, every court considering this ban has held it unconstitutional for a simple reason: It endangers women's health. Women's health should be protected by doctors, not put at risk by politicians. I hope for the sake of my patients and women throughout the country that the Supreme Court agrees.

Cassing Hammond is an assistant professor in obstetrics and gynecology at the Northwestern University School of Medicine and a plaintiff in National Abortion Federation v. Gonzales, a legal challenge to the federal abortion ban.