Endometrial Lining

Do you know how thick the endometrial lining should be around cycle day 10?  I just had an ultra sound done (I'm on Femara, and plan to do IUI this cycle) and my lining was 4 mm.  Last IUI cycle, my lining was 6.5, and I'm wondering what I can do to increase the thickness of my lining?  I never realized it was a problem, but now that I'm being monitored so closely, it seems to be.

Thanks.

[John Kim, M.D.]

The important question is how thick is the endometrial lining at the time of mature follicular development when you get the HCG trigger to ovulate. So if your follicle is around 18mm on cycle day 10 and the doctor wants to trigger, even the the lining is 4mm, I would suggest waiting to help thicken the lining. 6.5mm is at the lower limits of normal.  Femara should not really thin out the lining like Clomid, so I am wondering what is happening to you.
If your lining is an issue, I suggest moving on the injectable form of ovulation induction with human menopaual gonadotropin (HMG) or FSH because these should not thin out your lining.
Also IVF may also be an option.
Some doctor use estrogen patches to help thicken the lining around cycle day 10 but I usually feel that if you are requiring estrogen during a Femara cycle, it is time to consider moving on the injections or IVF.