Can scar tissue from manual vacuum aspiration (MVA) or endometriosis cause thin endometrium in a patient with polycystic ovary syndrome (PCOS), normal body mass index (BMI), and dyslipidemia, who is undergoing fertility treatment with letrozole?

Can Scar Tissue from MVA or Endometriosis Cause Thin Endometrium?

Yes, scar tissue from manual vacuum aspiration (MVA) can cause thin endometrium through intrauterine adhesions (Asherman's syndrome), but endometriosis itself does not directly cause thin endometrium—though its surgical treatment may.

MVA and Intrauterine Adhesions

• Uterine instrumentation including MVA can lead to intrauterine adhesions (Asherman's syndrome), which is a well-established cause of thin endometrium and impaired endometrial receptivity 1
• Hysteroscopic adhesiolysis is the primary treatment for adhesion-related thin endometrium, though it achieves only modest improvements in endometrial thickness and pregnancy rates 1
• If you have a history of MVA, hysteroscopic evaluation should be performed to rule out intrauterine adhesions before proceeding with fertility treatment 1

Endometriosis and Endometrial Thickness

• Endometriosis itself does not cause thin endometrium—the disease involves endometrial-like tissue outside the uterus, not intrauterine scarring 2, 3
• Women with endometriosis are at increased risk of infertility (approximately 50%), but this is through mechanisms other than endometrial thinning, such as chronic inflammation, altered peritoneal environment, and ovarian reserve compromise 4
• Surgical treatment of endometriosis (particularly ovarian surgery for endometriomas) can potentially compromise ovarian reserve and function, but does not typically cause intrauterine scarring or thin endometrium 4

Letrozole and Endometrial Effects in PCOS

Importantly for your fertility treatment context, letrozole actually has favorable effects on endometrial thickness compared to clomiphene citrate:

• Letrozole produces significantly thicker endometrium (mean 6.9 mm) compared to clomiphene citrate (mean 5.9 mm) in PCOS patients 5
• Letrozole demonstrates better endometrial blood flow with lower spiral artery resistance (RI 0.63 vs 0.79) and pulsatility indices (PI 1.19 vs 1.55) compared to clomiphene 5
• Clomiphene citrate is notorious for causing thin endometrium (<0.5 cm) even in ovulatory cycles, whereas letrozole avoids these unfavorable endometrial effects 6
• Women treated with clomiphene have significantly thinner endometrium than those treated with gonadotropins (mean difference -0.33 mm), though endometrial thickness does not strongly predict IUI success 4

Clinical Algorithm for Your Situation

Given your PCOS, normal BMI, and letrozole treatment:

1. First, determine if you have a history of uterine instrumentation (MVA, D&C):

   • If yes → perform hysteroscopic evaluation to rule out Asherman's syndrome 1
   • If adhesions found → hysteroscopic adhesiolysis before continuing fertility treatment 1

2. Assess for endometriosis symptoms (chronic pelvic pain, dysmenorrhea, dyspareunia):

   • If symptomatic → transvaginal ultrasound (82-90% sensitivity for endometriomas) 2
   • Consider laparoscopy for definitive diagnosis if imaging indeterminate 2
   • Note: Endometriosis diagnosis does not explain thin endometrium 2, 3

3. Continue letrozole as your ovulation induction agent rather than switching to clomiphene, as letrozole provides superior endometrial development in PCOS 6, 5

Treatment Options for Thin Endometrium

If thin endometrium persists despite letrozole:

• Hormonal manipulation with estrogen supplementation 1
• Vasoactive measures: aspirin, vitamin E, pentoxifylline, L-arginine, or sildenafil 1
• Intrauterine G-CSF infusion 1
• However, most treatments achieve only minor improvements in endometrial thickness and pregnancy rates 1

Important Caveats

• Your normal BMI is favorable, as obesity can worsen PCOS metabolic features and potentially affect treatment response 4, 3
• Monitor your dyslipidemia closely, as both PCOS and endometriosis (if present) increase cardiovascular risk 3
• The coexistence of PCOS and endometriosis occurs in some women and may require management of both conditions to optimize fertility outcomes 2