AMH - Understanding the results - Dr Mary Birdsall
20 February 2018
To help with the questions around AMH - Dr Mary Birdsall has written a blog on the AMH and results.
About the AMH Test
AMH stands for anti mÜllerian hormone and is produced by the medium sized immature eggs in the ovaries. It is a powerful test because it gives an indication of likely menopausal age, likely reproductive time frame and likely response to drugs in an IVF cycle (how many eggs you are likely to get). AMH also can be used to confirm polycystic ovary syndrome and gives a guide to egg quality. However what AMH cannot tell you is whether you are going to have a baby.
There are some shortcomings of the AMH test which are becoming more apparent. Firstly, some places charge for the test. For instance, in the North Island of New Zealand it may cost between $80 to $100 and in the South Island free!
Many GPs won’t know how to interpret the result because it is a new test so hence this blog. AMH levels are also lower when ovaries are suppressed like when you are on the pill, pregnant or breast feeding.
I often see young women who have had their AMH checked whilst on the pill and their result is low and they are super anxious. I ask them to stop the pill for 2 to 3 months and in many instances, their AMH levels are much more reassuring.
The units that AMH is reported in is also different country to country. In NZ results are reported in picomoles per litre. Other places it is nanograms per mil. To convert nanograms per ml to picomoles per mil you multiply the result by 7.14.
The assay for AMH which is the way the lab performs the test is also a bit variable. What this means is a woman may have a blood test to check her AMH and gets a certain result and then if she repeats that test 1 week later the result is likely to be a bit different so as much as we would like this to be an exact science it is not.
So let’s get down to some real examples
- Say a 35 year old woman has an AMH level of 20 pmol/l which sits on the thick black 50th centile line. This means she has an average number of eggs left in her ovaries. What does average look like? Average means she is likely to have her menopause at the average age (51 to 52) and is likely to be able to have babies until she is around 41 (IVF may push this up a wee bit) and she is likely to get an average number of eggs in an IVF cycle.
Normal AMH levels are the easy ones to interpret but the ones outside the normal range are trickier.
- Take another example, 35 year old woman with an AMH level of 10pmol/l. She is now in our orange zone, which is probably a reduced ovarian reserve. Her level sits on the 25th centile and she is likely to have menopause around 49 as opposed to 51 and will also have a slightly shortened time frame to complete her family more like age 39 to 40. She is also probably going to produce fewer eggs if she did an IVF cycle and we would give her a higher dose of ovarian stimulation drugs.
- For my next example, what about a woman with a very high AMH level, maybe aged 35 but with an AMH level of 60 pmol/l. This woman is likely to have polycystic ovaries, you cannot predict her menopausal age , although menopause will not be early, and she will respond super well to ovarian stimulation drugs so would be given a lower dose of ovarian stimulation drugs.
- Lastly, I wanted to talk about very low AMH levels. The lowest result is less than 1.1pmol/l. Say the 35 year old woman had an AMH of less than 1.1pmol/l what does this mean for her? Firstly, I would want to know whether she is having regular periods (good) and also would want to check her FSH level which is another measure of ovarian reserve. This is done on day 2 or 3 of the period and an oestradiol level is checked simultaneously. Having a lowered AMH means that menopause will be early, but it is impossible to predict exactly when, time is limited to have babies, and that she will produce few eggs in an IVF cycle (sometimes none) and has a lowered chance of having a baby but it is not zero and there is still the possibility of having a baby naturally, provided everything else is OK. The risk of miscarriage may also be increased. We have looked at more than 500 women doing IVF at Fertility Associates with an AMH level of less than 1.1 pmol/l and have a take home baby rate of 13%.