Chronic stress during pregnancy reduces babies' iron, study finds

Chronic stress during pregnancy is bad for fetal development and pregnancy outcomes, many studies have shown.

New research from the University of Washington and the Technical University of Munich reveals how prenatal stress can decrease how much iron the baby gets. And iron is crucial for brain development and cognition.

The researchers started by giving 2,000 pregnant people a questionnaire asking them how stressed they were.

“We wanted to identify the participants based on how they feel, not based on what a biomarker says,” said Dr. Martin Frasch, a researcher at the University of Washington and one of the study authors. “Stress is highly subjective.”

Stress is a common problem during pregnancy, Dr. Frasch added: About a quarter of the participants who completed the questionnaire were very stressed.

After sorting the study participants based on their self-identified stress levels, the researchers gave them an EKG and looked at how much cortisol was in the participant’s hair; the hair closest to the scalp gave them information about the last three months.

The researchers also checked the iron in the participants' blood, and in the cord blood. The stressed individuals were not lower in iron than the control group — but the cord blood showed that, somehow, stress was reducing how much iron the babies got. The effect was greater for male fetuses than females.

To find out how the reduced iron might have affected the babies’ cognitive development, the researchers are following up with the babies when they’re two and five years old. Past research has found that anemia during the first trimester is associated with autism, ADHD, and intellectual disabilities. But it’s unclear what effect the reduction these researchers found in how much iron was available to the fetus later in the pregnancy might have.

Frasch said, for him, the takeaway of this research is that there are "opportunities to detect stress noninvasively in pregnancy [e.g., using a questionnaire or an EKG] early enough to introduce interventions."

He said it's often hard to address the root causes of chronic stress, like food or housing insecurity or financial problems, except through policy. But he and his colleagues are looking at whether managing stress with interventions like yoga or meditation might help reduce the impact of stress on fetal development.