primary amenorohea(delayed onset of periods)

The simple answer for this will have to be "most likely nothing, but possibly a lot" so i suggest we go through the detailed answer. No short cuts this time!

The main reason for writing this detailed answer is because often a girl such as this may be told simply that it could be a problem with genetics or with hormones. That can scare her un-necessarily. Seeing a doctor is a good idea but being scared by the internet is not!

There could be dozens of reasons why a 16 year old may have not had her first period but thankfully the most common reason is a unexplained delay in menarche. You will be pleased to know that this has no bearing on health or problems in the future, especially fertility. Basically just a matter of chance that your periods have not started "in time".

If you are a student of mathematics or statistics you know that in a "normal distribution curve" or Bell's Curve, around 97% of the subjects will fall within two "standard deviations". The age of 16 is the top end of this range of two standard deviations. It doesn’t mean that somebody who begins her menstrual period six months later, is abnormal. Just less common than expected.

However since menstruation is so closely linked with fertility, it is obviously a cause for concern more for the parents than for the girl herself. I will list the five main groups of causes of primary amenorrhoea(absence of periods) which are most likely..

1. An unexplained delay with no abnormality including no obvious mental stress – this would cover perhaps the vast majority of the cases.

2. Imperforate hymen- this is more relevant in countries like India with very low pre-marital sexual activities. In societies where early initiation of sex is common, this problem will be noticed and sorted by medical intervention much earlier.

3. Physical or Mental problems ranging from mental stress and Anorexia Nervosa, medications for psychosis to serious general infections such as tuberculosis etc.

4. Various gynaecological problems ranging from stenosis of cervix or under-developed uterus, ovaries being absent (agenesis), hormone producing tumors, pituitary problems etc.

5. Serious high achieving high performance athletes especially gymnasts, long distance runners etc. who have very low body fat and very intensive and mentally stressful training regimes.

The point to note in the above list is if you have any of these problems you should not worry, because most can be resolved quite easily.