(Bloomberg Opinion) -- The U.S. has a weirdly high maternal death rate. It’s a symptom of a sick health care system.

The number of women dying of complications of pregnancy and childbirth is going down in all developed countries except the United States. New statistics released last week show that the U.S. maternal death rate has continued to climb, and is now four to six times higher than in many European countries.

This problem is tied up with the country’s rising rates of heart disease and the way cardiovascular deaths are creeping into younger age groups. People tend to associate heart disease with older men, but almost as many women die of heart disease. In fact, it’s the number one killer of women, and can also affect women of childbearing age.

The new CDC numbers measure deaths during pregnancy and up to 42 days after delivery. They give a figure of 17.4 per 100,000 births, or 658 women per year, with a big racial discrepancy. The rate is 14.7 per 100,000 for white women and 37.1 for African American women.

Those numbers don’t reveal the whole picture, says Nandita Scott, cardiologist at Massachusetts General Hospital and Assistant Professor of Medicine at Harvard Medical School.

Pregnancy puts an enormous stress on a woman’s cardiovascular system, imposing changes that last well beyond the 42 days. When you look at maternal deaths up to a year after delivery, those numbers look even worse. For African American women, the CDC shows a death rate of 42.4 women per 100,000 births.

The effects of pregnancy on the human body are amazing, she said in a talk she gave the day before the CDC released its new figures. Heart rate goes up, dilutional anemia occurs, blood volume increases and cardiac output increases by 30-50%. To prepare the pelvic area to deliver the baby, hormonal changes occur that can also weaken the blood vessels, and that can put some women at risk for a tearing of the arteries.

Since she didn’t have the latest CDC numbers at the time she gave her talk, she used a combination of older numbers and data from the Global Burden of Disease Study, published in 2016 in the journal The Lancet. All the numbers showed a consistent problem: Pregnancy imposes a massive physical strain that can be fatal for women with pre-existing health conditions. And increasing numbers of U.S. women are entering their pregnancy less healthy.

To be sure, the statistics show that many maternal deaths in the U.S. can be attributed to issues unrelated to heart disease, such as hemorrhage or infection, or the result of mental illness. But 30% to 40% of the maternal deaths in the U.S. are associated with cardiovascular problems, such as cardiomyopathy (an enlarged heart), blood pressure abnormalities known as pre-eclampsia and eclampsia, and embolism (artery-clogging blood clots.)

Tennis star Serena Williams suffers from a clotting disorder and nearly died from an embolism after giving birth to her daughter in 2017. According to her account of the ordeal in the New York Times, she knew she was prone to blood clots, but had trouble convincing the hospital staff to treat her for them when she started realizing there was a problem.

Scott said it’s not standard for cardiologists to get training to deal with pregnant women. But as one of the few women in her field — the only one in her fellowship class — she started looking into the problem. “I don’t think cardiologists knew we needed to be part of the solution,” she says.

Why has the problem gotten worse in the United States but not in Europe? Scott says it’s a combination of factors. U.S. women are more likely to have untreated cardiovascular problems and less likely to get proper healthcare during and after pregnancy. The quality of U.S. healthcare is variable from one region to another. And in the U.S., women have been getting more caesarian sections, which put them at risk of more complications than vaginal births.

Access to birth control is another problem that affects many women in the United States. Cardiologists sometimes advise women with high risk heart problems not to get pregnant, but may not follow up on how patients can safely achieve this. There are different contraceptive recommendations depending on the severity of your cardiovascular condition.

And there’s been too little awareness. States vary in their reporting diligence, and many hadn’t been regularly indicating pregnancy on death certificates. The new CDC numbers come after an eleven-year gap because public health officials hadn’t been able to successfully track the problem. Scott said this lack of surveillance is disturbing considering how badly the U.S. is doing compared to its peer group.

The good news is that California has started an effort to improve maternal health care and started to lower maternal mortality. And other countries demonstrate that the maternal mortality rate in the U.S. isn’t a biological inevitability, but something but something that can be extremely rare when women get good health care in pregnancy and beyond.

To contact the author of this story: Faye Flam at fflam1@bloomberg.net

To contact the editor responsible for this story: Sarah Green Carmichael at sgreencarmic@bloomberg.net

This column does not necessarily reflect the opinion of Bloomberg LP and its owners.

Faye Flam is a Bloomberg Opinion columnist. She has written for the Economist, the New York Times, the Washington Post, Psychology Today, Science and other publications. She has a degree in geophysics from the California Institute of Technology.

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