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New Delhi: Girls getting their first period early grow significantly taller than the previously thought amount of 6-8 centimetres, according to a study that followed nearly 800 women in Sweden from birth to adulthood, through puberty.
Researchers found that the onset of menstruation at or before 12 years of age typically grew taller by almost 13 centimetres, whereas girls attaining puberty at or just over age 14 typically grew taller by three centimetres in height.
The researchers from the University of Gothenburg, Sweden, said that while there is a widespread belief that girls grow 6-8 centimetres after their first period, among the study participants, only one in two grew to this extent.
"With this study, we show that there is a huge variation and that those who enter puberty early and get their first period early grow significantly more than previously thought, and that those who are late in getting their first period do not grow that much more," lead author Anton Holmgren, a pediatric researcher at the University of Gothenburg, said.
Data for analysis, published in the journal Frontiers in Pediatrics, was collected through participant surveys, interviews and a national registry. The heights of the participants' parents were also included.
"Our study shows that girls with early menarche (before 12 years of age) have a (typical) height gain of 12.8 centimetres post-menarche, whereas girls with menarche above 14.2 years of age have a (typical) height gain of just 3.1 centimetres after menarche," the authors wrote.
The researchers also found that the average age of girls when they had their first period was 13 years, and the girls typically grew taller by seven centimetres, which they said is considered normal. Overall, the growth in the participants' height ranged between 0.2 centimetres and 31 centimetres.
"This variation in growth after menstruation and to final height is much greater than previous studies have shown. The variations depend very much on when they get their period. There is a huge difference between those who get their period early and those who get it later," lead author Jenni Gardstedt Berghog, a doctorate student at Halland Hospital, Halmstad, Sweden, said.
The researchers also found that age at menarche was inversely related to childhood body mass index (BMI) -- a high BMI in childhood could indicate an early onset of menstruation, while a low BMI could indicate a late onset, they said.
Early onset of periods has been related to being overweight or obese in adulthood and risk of heart disease. One of the indicators of obesity is a high BMI.