hello Oh, what is your girlfriend from unsolicited period once a year to do? Do you have a girlfriend menarche to now how long? the average child in the after menarche, within six months to one year period is not regular , the blood has been uneven, long time interval is short, this is not true menstrual disorders, since the time of menarche, ovarian development is not mature, controlled ovarian endocrine system is not perfect, which makes the laws of menstruation can not be formed without fixed periodicity, perhaps a year or so, but could not come through, sometimes even come, but also perhaps for the anovulatory menstruation. This increased with age, the body's regulatory mechanisms to improve gradually improved, until the recovery to normal.
check your girlfriend can be a sex hormone, B-ultrasound, about hormones and uterine, ovarian conditions, rule out the possibility of disease, then that is what I have said physiological, is normal, do not worry, it will increase with age and return to normal, but also some people to the menstrual cycle is once a year, after the examination is normal, then will be pregnant, please Do not worry!