As conservatives wage an ongoing legislative war against abortion, a new study stresses that restrictive laws are detrimental to the health of pregnant people.

Published today (June 11) in Annals of Internal Medicine, the study was conducted by researchers at Advancing New Standards in Reproductive Health (ANSIRH). It is the first study to compare the health of people who were denied an abortion to those who were able to obtain one, and it shows that those who gave birth after being denied an abortion faced greater long-lasting health risks and are more prone to chronic illnesses.

The study focused on 874 people who sought an abortion between the years 2008 and 2010. Of those, 328 had an abortion during the first trimester of pregnancy, 383 in the second trimester and 163 were denied the medical procedure because of gestational age limits in their state and went on to give birth.

Researchers asked each person to self report pain, chronic conditions and overall health at the beginning of the study and semi-annually for the next five years, through December 2015.

According to Time:

At the study’s outset, about 20 percent of women who had a first-trimester abortion described their pre-pregnancy health as fair or poor, compared to 17.5 percent of those who had a second-trimester abortion and about 18 percent of those who were turned away. After the five years of follow-up, about 20 percent of women who had an abortion at either stage of pregnancy reported fair or poor health—but among women who went on to give birth, the share of those reporting fair or poor health had risen to 27 percent.

Additionally, two of the people who gave birth died of maternal-related causes during the course of the study.

One of the study’s authors, Lauren Ralph, an assistant professor of obstetrics, gynecology and reproductive sciences at University of California San Francisco, told Time. “There’s a good deal of research that shows, in the short term, having an abortion is much safer than childbirth, but there isn’t much research over the long-term. Our study demonstrates that having an abortion is not detrimental to women’s health, but being denied access to a wanted one likely is.”

The findings were released as legislators pass restrictive state laws that will result in fewer people being able to have abortions. In the past year, Kentucky, Ohio, Georgia and Mississippi have passed bills prohibiting abortion after six weeks of pregnancy. In Missouri, it is prohibited at eight weeks. Alabama’s newest law, passed last month, criminalizes abortion from the moment of conception.

“The argument that abortion harms women is certainly not supported by our data,” Ralph told Time. She added, “The findings from the study can really highlight some of the consequences if we continue to restrict access to wanted abortion.”