My daughter just turned 17 and she has irregular periods - some are 4 months apart - she had one in june and july - but none since then. should i be alarmed? and what should i do? she is not sexually active.

See below: I would not be alarmed. However, she should see a gynecologist. She may benefit from ocps.

Consult an OB/Gyn: Although this is not the expected pattern for a woman's menstrual pattern it dose happen with some frequency. The ob/gyn can often give you some answers about how ocp's can create predictable cycles & the impact of this pattern on your daughters fertility later on. Sometimes they can obtain needed data from an abdominal ultrasound & avoid the discomfort of a pelvic exam . Good luck.