(NewsNation) — Women are getting their periods earlier than ever, and it’s taking longer for them to regulate, a new study published in the JAMA Network Open found.

Researchers analyzed data from 71, 341 American women born between 1950 and 2005 who participated in the Apple Women’s Health Study, finding that younger generations started their first period, otherwise known as menarche, earlier than older generations.

Lead study author Dr. Zifan Wang, a postdoctoral research fellow at Harvard University’s T.H. Chan School of Public Health, told CCN that they also discovered it took longer for menstrual cycles to regulate in younger generations.

The trend of young girls getting their period at younger ages has raised some alarms. Researchers wanted to find out why there has been a shift and what may be causing it.

Possible problems of early periods

Dr. Eve Feinberg, associate professor of obstetrics and gynecology at Northwestern University’s Feinberg School of Medicine in Chicago, told CNN that an early period may cause some problems or could indicate underlying issues, especially in the future.

She used an 8-year-old going through puberty as an example.

An 8-year-old going through puberty might have a disconnect between her mind and body, Feinberg said. Her body may be maturing at a rate that doesn’t necessarily keep up with her mind’s development, she explained.

An issue that this poses is the possibility of imbalanced hormones, especially with irregular menstrual cycles. Feinberg explained that the longer women have irregular periods, the longer the imbalance between estrogen and progesterone hormones.

Feinberg said those two hormones are essential to the growth cycle: Estrogen is needed for growth, and progesterone is needed to stop or slow growth. This is particularly important when it comes to preventing future health issues such as heart disease and cancer.

“You want to make sure that the body is regulated,” Feinberg said. “And when cycles are not regular, it’s generally a sign that something else may be going on.”

Why are kids getting their periods earlier?

Wang said that earlier periods in kids could be associated with obesity during childhood or other environmental factors, including nutrition or microplastics.

“This implies that childhood obesity, which has been increasing in the US, might be contributing to people getting their periods earlier,” Wang said.

Feinberg suggested that if this is the case, it’s always good to have physicians evaluate kids who get their period earlier to make sure they are in good health. She said it also helps to prevent any possible health issues in the future or catch any issues early on.