I’ve seen a lot of good questions come across the blog, and I will get to them in the near future.
What makes one woman’s lining thicker than another’s? Probably the only thing we know that makes a difference is uterine surgery. Now don’t everyone panic if you have had uterine surgery. Only very small percentage of women will have a problem, and if you need it, uterine surgery can be a good thing.
The surgery/thickness issue is related to scar tissue. Scarring in the uterus can make the lining thinner. Now there are 2 aspects of this. One is a local thinning. In this case, ultrasound can show a normal lining in part of the uterus, but a thin or absent lining in another area; where the scar is. Sometimes however, even when the scar is in one area, surrounding normal areas may look thin, and these thin areas thicken up after the scar is cut away. In this case it may be that the local scar keeps the 2 sides of the uterus tightly close to each other, and when the scar is cut, the front and back sides are not as close to each other and the lining can grow more thickly.
This last sentence requires a little basic explanation. You see, most people think of the uterus as a globe, round and hollow in the middle. While this is kind of true, the uterus is more like a peanut butter sandwich. The muscle is like the bread, and I call these the sides, or sometimes I say “front and back”, and the lining is like the peanut butter. So imagine areas where there is no peanut butter, the sides are touching in the middle. ( I must say I really hate food analogies, but I can’t think of a better way to say this.) So at hysteroscopy, we cut the scar, and the lining re-grows from the good areas. Of course, during pregnancy the uterus rounds out and becomes the globe.
The second aspect of thin lining and scar tissue is a little different. Here, even though the scar may be in one local area of the uterus, the entire lining gets affected. Last time we spoke about how the lining regenerates from the few glands beneath. Well for some reason, sometimes all of the cells that are supposed to make the new glands don’t work well. As an example, I once had a patient who came to see me because her uterus had been perforated during a hysteroscopy. Now usually such a perforation is localized. It’s a hole in just one spot in the uterus that usually heals well. In her case, yes the hole healed closed, but the lining throughout the entire uterus would not grow thick.
What this may be telling us is that when the uterus becomes damaged in one place, something is released to the surrounding areas of the uterus that permanently affects the ability of the lining to grow well. It may be a result of the injury, or maybe the injury allows for a small infection to start and cause damage. We really do not know how this all works, we just know that in some women, this is the story.
Should you have a hysteroscopy if your lining is really thin? Maybe. You should start with a hysterogram or sonohysterogram. I usually prefer the hysyerogram, but in some patients the sonohysterogram is ok. Some people need both. If these tests show scaring, then yes surgery may be indicated. If the cavities look completely normal, a hysteroscopy may not help because “looking in” without having anything to fix will not do anything to help.
I had one woman with a perfectly normal lining, got pregnant with IVF, and after a vaginal delivery, had a very very thin lining. Who knows, maybe a small infection, uterine tear or neither. A first trimester abortion, or d and c for miscarriage may cause this, but the odds are really low.
And there are some women who have never had surgery or a baby, who just have a thin lining.
Next tine I will discuss if a thin lining matters and ways we try to get the lining thicker.