Discover How Menstruation Affects Girls' Physical Growth: Key Findings From Recent Study

Imagine this: a 13-year-old girl has her first period, and according to most pediatricians and textbooks, she should grow about 6–8 centimeters taller before reaching her final height. But what if that same girl shoots up 13 centimeters, or barely grows at all? This is precisely what a recent study from the University of Gothenburg has revealed—girls' growth spurts after their first period are anything but predictable. In fact, the variety is striking.

Published in Frontiers in Pediatrics, the study dismantles the once-assumed uniformity in post-menarche height growth, suggesting that half of all girls grow either more or less than the anticipated 6–8 centimeters. One participant grew an impressive 31.1 centimeters, while another barely saw an increase of 0.2 centimeters. The range of growth is far wider than many had imagined, challenging long-held assumptions in both medical education and parental expectations alike.

The study included 793 women from southwest Sweden who were tracked from birth through adulthood. The data—which incorporated everything from childhood BMI to parental height—showed that the average girl had her first period at around 13 years old. The timing of this milestone was found to be key to her subsequent growth. Those who experienced menarche before the age of 12 grew substantially more, with a median post-period height increase of nearly 13 centimeters. Conversely, girls who had their first period after the age of 14 grew only about 3 centimeters on average.

So what does this all mean? According to Dr. Jenni Gårdstedt Berghog, one of the lead authors, the research flips the common narrative on its head. "The variation is much greater than previously shown. Those who get their period early grow significantly more than we thought, and those who are late do not grow that much more."

But it's not just the timing of menstruation that influences this growth. The study highlights the role of childhood BMI in shaping these patterns. A low childhood BMI, often tied to later onset of menstruation, tends to result in taller adults. On the other hand, girls with a higher childhood BMI, who are often early bloomers, are more likely to reach shorter final heights. These findings, measured on a group level, still allow for significant individual variation, leaving room for more personalized growth predictions in the future.

Dr. Anton Holmgren, the principal investigator, underscores the broader importance of these findings. "This study shows that there is a huge variation. Increasing knowledge in this area is good even if it is not linked to any disease. How you grow, when puberty occurs—it's something that everyone has a relationship with," he explains. And while the medical world tends to focus on growth in terms of disorders and abnormalities, this study highlights the normal—but extraordinary—diversity in human development.

In essence, when it comes to how girls grow after their first period, the story is far more nuanced than we once believed. Maybe it's time we tossed out the 6–8 centimeter rule and embraced the fact that, much like the rest of life, growth doesn't follow a straight line.