Wendy said: Technically no, it's not a big deal (though I'm a little surprised there is no bleeding with a Nuva ring, cause usually the every 4th week removal causes that....)
If there is no bleeding with either oral contraceptives, a hormone IUD or the Nuva ring, it just means that the estrogen component balanced with the progestin component is so low that there isn't much endometrial tissue developed at all. Plus, especially with the hormone iud's, there is no "withdrawal" of the progestin to trigger the message to slough off the endometrial lining (ie start bleeding).
Most important is when/ if these women want to conceive: they need to have at least a few periods on their own prior to trying to conceive, just to be sure the endometrial lining is back to normal. So, IUD out/ stop oc's or nuvaring and use condoms til there have been at least 2 cycles. Otherwise, this abnormally-thin uterine lining might be problematic for the placement of and development of a healthy placenta.