Thin endometrial lining - this is also uncommon. We like to see a lining of at least 8mm in thickness when measured by ultrasound at the time of maximal thickness during the cycle (see above ultrasound picture of an 11.2 mm lining).
- There is some debate about "how thin is too thin", as well as to "how thick is too thick".
- In general, 8-13 mm is good, less than 6 is potentially a problem, and greater than 15 or so might possibly reduce chances for successful pregnancy.
- During IVF treatment, the uterine lining starts at about 3mm thick at the end of the menstrual period. After estrogen levels rise sufficiently, the lining of the uterus then thickens by about 1mm each day during IVF.
Hysteroscopy is a surgical procedure that involves insertion of a narrow telescope-like instrument through the vagina and cervix into the cavity of the uterus (endometrial cavity). The cavity is then distended with fluid (such as salt water) and can be visualized through the scope. This procedure allows us to determine whether there are defects inside the cavity.

A uterine polyp on the "floor" of the uterine cavity - seen with hysteroscopy
Normal uterine configuration vs. uterine septum
Ultrasound, particularly 3D ultrasound, a newer technology, is very useful in characterizing the shape of the uterine cavity

Ultrasound of a normal uterus in the coronal plane
The endometrial cavity has a smooth triangular shape
Cervix is at the bottom of the image
A uterine septum on a coronal plane from 3D ultrasound study
Endometrial lining and uterine cavity = C
Muscle part of uterus = M
Septum "pushing down" into cavity = S
A septum in the uterus is like extra muscle "pushing down" from the top into the cavity.

This ultrasound image is a coronal plane showing a unicornuate uterus
The cavity (at "C") only goes to one fallopian tube (goes up to her right tube)
The other side of the uterus and tube are congenitally absent
Congenital uterine abnormalities of the uterus such as a unicornuate or septate uterus can cause reproductive problems such as miscarriage and preterm labor and birth.

Office hysteroscopy image of a uterine septum looking up from cervix towards top of uterus
Septum dividing the cavity at "S"
The left side of her uterine cavity is at "L", the right side is at "R"
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