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Secondary Sexual Characteristics and Menses in Young Girls Seen in Office Practice

Original article authored by: Marcia E. Herman-Giddens; Eric J. Slora; Richard C. Wasserman; Carlos J. Bourdony; Manju V. Bhapkar; Gary G. Koch; and Cynthia M. Hasemeier

This summary includes the following sections:

Background

Over the past several decades, researchers, teachers, and parents have observed that girls seem to be entering puberty earlier than in the past. Is this really the case? Until this study was conducted, very little substantive research had been done to try to answer this question. In fact, the standard research study on this topic was published in 1970, and its scales (the Tanner stages) are still used today.1 The authors note that until their own study, "no large-scale studies on sexual maturation have been published on racially diverse groups of girls from the United States younger than 12 years of age."

Study Purpose

The researchers who conducted this study wanted to update existing knowledge of puberty's onset among girls aged three to 12 — a much younger cohort than most previous studies. Moreover, they explored differences by race by comparing these characteristics among White and African-American girls.

Why is it important to track the onset of puberty and the changes associated with it? The authors point to several reasons:

  • If pediatricians are seeing younger and younger girls with early breast development, pubic hair growth, and menstruation, they need to be prepared to detect and discuss these changes with their patients.

  • The timing of sexual education in schools may have to be adjusted over time to incorporate these findings.

  • Early hormonal changes — and changes that vary according to race and ethnicity — may have implications for other types of surveillance, such as tracking environmental causes or links to breast cancer or other conditions later in life.

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Methods

The American Academy of Pediatrics (AAP) sponsors a network of pediatricians who participate in various research studies. Patients of this group, known as the Pediatric Research in Office Settings (PROS) Network, formed the study sample. Pediatricians who participated in the study received special training in how to detect and rate changes in breast development and hair growth. In order to participate in the study, they also had to pass a test on their ability to consistently note and record these changes.

Ultimately, 225 clinicians — representing 65 different practices — collected data for the study. The sample included girls between the ages of three and 12 who received physical exams from the participating PROS pediatricians. Some girls received the exams for routine reasons — such as well-child visits — while others received exams because of a specific concern, such as stomach cramps.

Data collection sheets were completed for 18,549 girls, but 976 (5.3%) of these were deleted from the study sample because of missing data or because they were outside the age range. Another 2.8% of the girls in the sample were dropped because their races constituted such a small part of the total that no conclusions could be drawn about them. The remaining 17,077 girls were 90.4% White and 9.6% African-American, with girls of Hispanic ethnicity represented in both groups.

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Findings

Analyzing the data collected by participating clinicians, the researchers found that girls in general begin puberty earlier than standard pediatric textbooks suggest — and earlier than previous studies have found. The authors report that textbooks and other types of guidance suggest that about 1% of girls younger than eight have one or more of the characteristics they measured, but their study found much higher percentages for both African-American and White girls. (For example, they found that at age seven, 27.2% of African-American girls and 6.7% of White girls already showed evidence of breast and/or public hair development.)

On average, the researchers found that African-American girls begin puberty when they are between the ages of eight and nine; White girls begin puberty, on average, by the time they are 10. For each specific characteristic that was measured — breast development, pubic hair growth, and axillary hair growth — African-American girls developed earlier and faster than their White counterparts. The researchers are not sure why this is the case. The pattern persisted even when they controlled for height and weight.

The researchers discussed several possible limitations for their methods, including the possibility that patients seen in clinical settings are not representative of the general population of girls, or that younger girls might be more likely to be brought to a clinic by their parents precisely because of a concern about early development. However, they did not find these possible sources of bias to be persuasive enough to explain their findings. For example, there is no evidence that girls seen in these clinics differ from the general population, nor that parents bring them to the clinics for these reasons.

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Implications

This study documents that early puberty is, in the authors' words, "a real phenomenon." This means that tools to measure early puberty should be developed and used, and should specifically take into account racial differences. This study represents a new baseline against which future changes can be measured, but in the meantime, pediatricians and other professionals who work with young girls need to explore and respond to the clinical, educational, and social implications.


1Marshall, W.A. & Tanner, JM. (1969). Variations in the pattern of pubertal changes in girls. Archives of Disease in Childhood. 44, 291-303.

Herman-Giddens, M.E., Slora, E.J., Wasserman, R.C., Bourdony, C.J., Bhapkar, M.V., Koch, G.G., & Hasemeier, C.M. (April 1997). Secondary Sexual Characteristics and Menses in Young Girls Seen in Office Practice: A study from the Pediatric Research in Office Settings Network. Pediatrics. Vol. 99, 4, 505-512.

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