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PHILADELPHIA (CBS) — Two studies have been released on pregnancy, one linking pregnancy to heart attacks and the other is about an increased risk for Alzheimer’s disease.

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Research was published Wednesday by the American Academy of Neurology that covered 3,500 women in Korea and Greece.

It found that women who had given birth to five or more children were 70 percent more likely to develop Alzheimer’s disease, when compared to women who had fewer children.

Researchers say this could be related to increased estrogen levels that come with pregnancies.

If the findings are confirmed in other populations, doctors say hormone-based preventive therapy could be used to fight or prevent Alzheimer’s.

The other study on pregnancy says the number of American women having heart attacks during pregnancy or after delivery is rising.

Erika Perez welcomed her third child Joshua seven years ago. Right after his birth, she didn’t feel well.

Her EKG was normal, but 10 days later, she had pain in her chest, arm, and back and was dizzy. She had a massive heart attack.

“I never thought that being 37 and having my third baby, I was going to be having a heart attack,” said Perez.

A new study says the risk of having a heart attack during pregnancy and right after delivery is on the rise.

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Researchers examined 55 million hospitalizations and found a 25 percent increase from 2002 to 2014.

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“The risk of heart attack during pregnancy may be increasing because women are waiting longer to have children,” said Nathaniel Smilowitz, assistant professor of medicine at NYU Langone Health. “Diabetes and obesity have gone up during that same time period.”

Heart attack risk was highest for pregnant women over the age of 40. Doctors say it’s critical to know your risk factors, such as high blood pressure, cholesterol and diabetes, and don’t ignore the warning signs like chest pain.

“Although the risk of heart attack in women is low during pregnancy, it’s not zero and the complications of heart attacks during pregnancy can be serious,” said Smilowitz. “Pregnancy is a stress on the body and it can unmask heart disease in that setting.”

Perez, now 45, is encouraging other women to speak up if they feel something isn’t right.

“Know your body and know your symptoms,” said Perez.

Now, she is walking more and eating better to pass healthy habits onto her children.

The study published by the Mayo Clinic found 50 percent of women in the study who had heart attacks during or after pregnancy were under the age of 35.

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Another finding stated the highest number of heart attacks happened during the recovery period after birth.