| 1 | A girl's first period is called menarche (pronounced: meh-nar-kee). | |
| 2 | "The best sleep we ever get is between age nine and menarchy, " she adds ruefully. | |
| 3 | The women with elder brothers had started their periods almost a year later than others. | |
| 4 | Now scientists have found two genes involved in determining the onset of menstruation. | |
| 5 | It can take up to 2 years from menarche for a girl's body to develop a regular menstrual cycle. |