الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
For the last 40 years, the first line of treatment for anovulation in infertile women has been clomiphene citrate (CC).The choice of CC was appropriate because the drug was highly effective in inducing ovulation in selected patients with the advantages of being orally administered, relatively safe, and inexpensive .
In spite of the high ovulation rate associated with the use of CC (57–91%), the pregnancy rate is much lower (around 20–40%) , Moreover, there may be a higher than expected incidence of miscarriage in conception cycles following CC treatment.
Such discrepancy is believed to be due to the peripheral antiestrogenic effect of CC, particularly at the level of the cervical mucus and endometrium.
In addition to a discrepancy between ovulation and pregnancy rates with CC treatment, 20 to 25% of anovulatory women are resistant to CC and fail to ovulate at doses up to 200 mg daily.
Letrozole is a simple oral alternative to CC with no adverse effect on the endometrium and endocervix avoiding the risk of multiple pregnancy and ovarian hyperstimulation syndrome.
In our study ,we tried to compare the effect of cc and letrozole on the endometrium in PCOS patients using endometrial thickness and spiral artery Doppler as parameters for comparison.
Our study revealed that:
• Enometrial thickness was better under letrozole therapy.
• Spiral artery Doppler shows lower impedance with a lower RI and PI under letrozole therapy.
Many studies revealed that spiral artery Doppler is a good measure of endometrial receptivity with more pregnancy rate towards lower spiral artery impedance while others show no association between impedance of spiral artery and concep¬tion.
In our study Spiral artery RI and PI were apparently lower in the pregnant group, and the difference is statistically significant. However our study could not provide a cut off value of PI in spiral artery as a useful prediction of better endometrial receptivity in terms of subendometrial blood flow.
Spiral artery Doppler is not sufficient alone as a measure of endometrial receptivity. Using three dimensional power Doppler and incorporating uterine, ovarian and subendometrial blood flow may predict better endometrial receptivity for conception.