Study Reveals Long-Lasting Biological Changes in Women’s Bodies After Pregnancy

Biologists have created one of the most detailed physiological profiles of pregnancy and its aftereffects by analyzing around 44 million test results from over 300,000 births.

Published in Science Advances on March 26, the study, which used the anonymized results of blood, urine and other tests taken before, during and more than a year after pregnancy, reveals the scale of the toll that pregnancy and childbirth take on the body — from the myriad changes made to support a fetus to the effects of its abrupt departure from the body during birth.

The researchers used anonymized medical data from Israel’s largest healthcare provider, covering the years 2003 to 2020. They focused on women aged 20–35 who had no chronic illnesses or medications, analyzing results from 76 standard physiological tests. These included measurements of blood health, cholesterol, kidney and liver function, metabolism, inflammation, and immune response — collected from up to 4.5 months before conception to 18.5 months after childbirth.

The study found that pregnancy initiates complex, dynamic changes across almost every major system in the body. Jennifer Hall, a reproductive health researcher at University College London, said the findings challenge the societal expectation that women should quickly “bounce back” after childbirth. “This is biological proof that you don’t,” she added.

Recovery Period from Childbirth

The researcher examined the 76 physiological markers in hundreds of thousands of pregnancies, looking at how long it took for each marker to settle following delivery. The study looked at blood clotting, the muscoskeletal system, the endocrine system, the immune system, kidney function, liver function and red blood cell health.

According to the results, 47% of test results stabilize within 1 month of delivery. However, 12% took 4–10 weeks to return to pre-pregnancy levels, and 41% took more than 10 weeks.

Several markers, particularly those related to liver function and cholesterol, took approximately six months to stabilize, while others — like an indicator of bone and liver health — took a year. Remarkably, a few markers, such as those linked to inflammation and blood health, remained altered even after 80 weeks, when the study concluded.

The team classified the physiological changes into four distinct patterns. Some markers increased during pregnancy and dropped afterward; others decreased and then rebounded. In certain cases, the markers over- or undershot pre-pregnancy levels immediately after childbirth before gradually stabilizing. Researchers suggest this may reflect the body’s attempts to overcompensate during recovery.

Pre-Conception Changes

Beyond childbirth, the study also revealed changes that began even before conception. For instance, there were increases in folic acid and reductions in inflammation markers, which the researchers attributed to lifestyle changes such as improved nutrition and supplement intake by women trying to conceive.

One of the study’s most significant findings relates to pregnancy complications. The researchers compared test results from healthy pregnancies with those from women who developed conditions such as gestational diabetes and pre-eclampsia, serious conditions typically diagnosed during pregnancy. They discovered subtle physiological differences in certain markers even before conception. This opens the possibility of identifying women at risk of these conditions before they conceive, potentially allowing for preventive interventions.

Lead researcher Uri Alon, a systems biologist at the Weizmann Institute of Science in Israel, said he was astonished by how each test displayed detailed, week-by-week changes. “It took my breath away to see how elaborate these profiles are,” he remarked.

Plan to Follow Similar Approach to Study Menopause

The research not only provides a biological timeline of recovery but also underscores the long-lasting toll pregnancy takes on the body. Alon’s team now plans to apply a similar data-driven approach to study menopause. He believes this wealth of anonymized biomedical information could unlock many more insights into women’s health. “It’s like paradise,” he said.

This groundbreaking research reshapes the understanding of postpartum recovery and could lead to better healthcare strategies, recognizing that pregnancy’s impact lasts much longer than previously assumed.

Source: This article is based on a report originally published by Nature.