We all remember going through puberty, though some of us might like to forget. Now imagine starting that formative transition — developing breasts or pubic hair — at 6 years old, just as you’re starting first grade.
Now new research has found a likely cause: The heavier the mom-to-be, the more likely her daughter will bloom early, according to a Kaiser hospital study in Northern California.
Early puberty is a becoming a reality for many American girls, and it puts them at higher risk for depression and diseases such as breast cancer. A generation ago, only 5 percent of girls started puberty before age 8. Today, 27 percent of girls have already begun to develop breasts by then, and almost 20 percent have pubic hair.
Kaiser researcher and study lead author Ai Kubo said that most studies have looked at early bloomers themselves, monitoring their health, lifestyles and environments for possible triggers. Scientists know childhood obesity is associated with earlier puberty, but it doesn’t tell the whole story, Kubo said.
“There has been a trend toward earlier onset of puberty observed over the last few decades, and the reasons haven’t been sorted out,” she said.
To find answers, Kubo went back to the womb. Research has already shown that a mother’s health during pregnancy dramatically influences her baby’s development in those first nine months and long into the future, and a smaller previous study by Kubo suggested there was a connection between a mother’s weight during pregnancy and when her daughter starts puberty. Could it be the key?
The findings, published Monday in the American Journal of Epidemiology, looked back at the health records for over 15,000 mother-daughter pairs in Northern California. She and her coauthors noted each mom’s body mass index (BMI) and blood sugar in early pregnancy, then lined up the data with when her daughter started puberty. For girls, puberty begins with the first signs of breast development and the appearance of pubic hair.
The researchers found that daughters of obese and overweight mothers — with BMIs of 25 or more — were more likely to bloom early. Daughters of obese mothers or mothers with high blood sugar were more likely to show early breast development. High maternal BMI similarly shifted the timing of pubic hair growth among white, Hispanic and Asian girls.
Doctors need to note these differences between demographics, Kubo said. Though the onset of puberty has shifted for all American girls, some are affected earlier than others. For example, prior research has found that African American girls start breast development about a year earlier than white girls, on average, with 18 percent budding at just 6 years old. Researchers have looked at a number of possible causes, including socioeconomic stressors and higher rates of obesity, and hope to find the answer.
“Health disparities are just getting wider and wider — minority populations have worse outcomes, earlier puberty and more childhood obesity,” said Kubo. With different obesity rates, environmental conditions and socioeconomic pressures, early bloomers are subject to different triggers and doctors need to know what those are to plan interventions, she said.
Louise Greenspan, a pediatric endocrinologist and coauthor of the study, said despite the trend of earlier physical maturity, it is important to understand that “getting your period early does not mean you’re going to get breast cancer.”
“These are modifiable risks — people can take control and make changes.” Greenspan said. She sees many girls with early puberty and advises them to make healthy lifestyle choices. She and psychologist Julianna Deardorff published a guidebook called “The New Puberty” in 2014, which covers the potential triggers of early puberty and how to avoid its risks.
Simple lifestyle changes can also make a huge difference for moms, Greenspan said.
The new research shows that moms with high blood sugar were more likely to birth early bloomers. However, moms diagnosed with gestational diabetes were not, even though their blood sugar levels were highest of all. Kaiser Permanente has a program that teaches diabetic mothers-to-be to manage their blood sugar and weight, Greenspan said, and this intervention may have been what made the difference in theirs and their daughters health.
Rachael Cornejo knows the confusion and embarrassment of being an early bloomer. Now 19, she said she started puberty around the age of 9. Even with a pediatrician for a mother, the transition was challenging.
“Puberty is a time when you feel scared, you feel alone,” she said. “You feel like your friends aren’t listening to you, your parents don’t understand what you’re going through. Even the task of asking a male P.E. teacher to let you out of class because you’re on your period is terrifying.”
She participated in a different Kaiser Permanente study of early bloomers from age 7 to 15. As an adult, Cornejo now advocates for better and earlier education about women’s health, and said waiting to talk about puberty “in fourth and fifth grade doesn’t cut it for a lot of girls.”
“I was an early bloomer, and my mother was really supportive the entire time — but I had friends who that was not the case for,” she said. Girls who grow up without a doctor in the house often rely on parents who avoid the subject, health educators who are out of touch, or peers who can’t sympathize with them yet, she said.
“When you’re a girl, your principal educator about everything to do with being a woman is your mom,” said Cornejo. “I would advise all moms to take that seriously, and make sure their kids have them as a source of information no matter how hard those conversations are.”
Study: Mothers’ weight linked to daughters’ early puberty