I think most women were told a variety of information about when they could expect to get their first period. There is the idea that a girl can expect to start menstruating when she becomes the same age that her mother was, when her mother got her first period. Some have said that the amount of body fat a girl has plays a part in when she will start puberty. Researchers have discovered that there is actually a genetic link that affects when a girl will begin puberty, as well as when her first menstruation will occur.
Researchers analyzed 32 genome wide association studies, and then replicated those results in 14,000 women. There are 30 genes that have an effect on the timing of when a woman will get her first period. Four of these genes are linked to body mass index. Three have something to do with metabolism, and another three are involved in hormone regulation. Previous studies of twins reveal that half of the variation in the timing of a first period can be attributed to genetic factors.
What does this mean for genealogists? It means that there really is a connection between when a mother started puberty and menstruation, and when her daughters will. In general, women begin menstruating when they are somewhere between the ages of 11 and 14.
It also means that obesity plays a role in when a girl will begin puberty. American girls are beginning puberty at younger ages, some as young as seven years old. It appears that the body wants to begin puberty as soon as it has stored a certain amount of nutrients. It is unknown if starting puberty early is linked to health risks, but there have been suggestions that it might. There are significant health risks that are connected to obesity. If these genes run in your family, you may want to speak with a doctor to find out what health issues you need to be aware of.