In girls, breast development can begin any time between the ages of 8 and 13. (Later development may be considered “delayed” but is not necessarily abnormal.) As the breasts grow, pubic hair will begin to appear, and your daughter will grow very rapidly.
Keep in mind that a girl's breasts may develop at different rates, and there's nothing wrong with one breast being larger than the other during this time.
Early breast development can be a source of embarrassment, and if your daughter is among the first in her class to develop breasts, she may be very self-conscious about it. She may favor big shirts, and bras that flatten rather than “point” her breasts during these early days. She will probably be uncomfortable until some of her friends begin to develop, too.
Bra shopping is another milestone. It's actually become much easier, given today's wide fashion selection. While there's a limited selection of bras for the new wearer, your options increase with cup size.
Young girls who are developing often like the look of sports bras; otherwise, pick up one white or skin-colored bra for her to wear under white or light-colored shirts, and then let her select whatever other color and style she likes. Designers are making bras in every style, from zebra-stripe to polka-dot. They've certainly made growing up more fun! Let her enjoy it.
If your daughter chooses to use tampons, tell her about toxic shock syndrome, a relatively rare but extremely serious illness that can result from tampon use. To avoid TSS, doctors recommend changing tampons regularly, wearing a pad instead of a tampon at night, and using the lowest-absorbency tampon appropriate. (In other words, stuffing in a “super” and figuring she won't have to change her tampon all day is not a good idea.) Symptoms of TSS include a high fever, feeling faint, vomiting, diarrhea, chills, headaches, sore throat, rash, and a vaginal discharge. These are also symptoms of many other illnesses, but if your daughter does come down with a high fever or what seems to be a bad virus while using tampons, have her remove the tampon and check in with the doctor.
Approximately two years after the first sign of breast development, your daughter's first menstrual period will occur. (Your pediatrician will be able to give you a slightly more accurate timetable based on the progress of your daughter's development.) Prior to menstruation, glands within the female genital system often secrete a fluid ranging from clear to white in color and from watery to thick in consistency. This is quite normal and can persist for several years.
Early menstrual periods are almost always painless, because cramps don't usually occur until ovulation takes place (which can be 6–20 months after the onset of menarche). Irregular periods are normal and they will become more regular over time.
It's All in the Attitude
How you present menstruation to your daughter may have a big effect on her attitude. Just as some cultures celebrate boys becoming men, you might consider treating menstruation in the same positive light—as a celebration of the wonderful woman she is to become.
Mothers should avoid referring to menstruation as “the curse” or complaining about PMS or terrible cramps. Negative references will convince your daughter that she's entered a bleak phase of her life. (It's hard to persuade a 13-year-old that the “miracle of giving birth” makes it all worthwhile.) A positive attitude about the manageability of mood swings and menstruation will take her far.
Also check with your doctor. Tampons are very liberating, and many physicians will say that as soon as your daughter is willing to try, there's no problem with using them. (Learning to use tampons is an art; give her a box and show her the general directions on the instruction leaflet, then let her experiment. She'll get the hang of it after a few tries.)