several causes of infertility such have male factors ( 20%-25% ) , anovulation ( 15%-20% ) , tubal defects ( 15%-40% ) , endometriosis ( 5%-10% ) , and unknown etiology ( 20%-30% ) are documented . the advantages are low cost , easy administration , and high ovulation rate of 60%-80% . however , the disadvantage is low pregnancy rate of about 50% . letrozole , is a potent , highly specific nonsteroidal aromatase inhibitor with ovulation induction potential and high pregnancy rate of 80% , whichis due to its less antiestrogenic effect on endometrium . previous studies have compared the efficacy of clomiphene citrate and letrozole among western population ; however , the data of comparing the efficacy of these two drugs among indian population are lacking ; hence , the present study was designed . the study was conducted in the infertility clinic of mahatma gandhi medical college and research institute , pondicherry , india , during june 2008 to december 2009 . previous records if available were verified for the information such assemen analysis , tubal patency , hormonal assay , and use of any prior use of ovulation inducing agent / s . after ruling out male factor , tubal factor , local factor of infertility , the woman was followed through one natural cycle by transvaginal ultrasound ( wipro ge , logiq 200 , 6.5mhz transducer ) for follicular development . those who did not show the sign of follicular development by ultrasonography were randomized into two groups by using table of random number . group 1 consisted of 25 women receiving 50 mg of clomiphene citrate from day 2 to day 6 and follicular monitoring was done from day 10 onward till day 18 on alternate days . women , who did not show optimal follicular growth ( 20 mm ) , received 100 mg and 150 mg of clomiphene citrate in subsequent cycle for follicular development and were monitored for optimal follicular growth by transvaginal ultrasound . in group 2 , letrozole 2.5 mg was used from day 2 to day 6 and followed similarly to group 1 . women , who did not show optimal follicular growth ( 20 mm ) , received 5 mg and 7.5 mg of letrozole in subsequent cycle . both the groups were followed - up for the number of follicles , diameter of large follicle , endometrial thickness , and serum estradiol levels . women not responding to one drug were given the other drug but not included in the study . the mean ages ( 26.4  3.55 and 27.72  3.33 years ) and body mass index ( 24.31  1.27 and 24.43  1.21kg / m ) of women were similar in group 1 and group 2 , respectively . the numbers of patients with primary infertility were 21 and 22 in group 1 and group 2 respectively , while secondary infertility was observed in 4 and 3 patients from group 1 and group 2 , respectively [ table 1 ] . profile of the subjects seven women had one follicle , seven women had two follicles , three women had three follicles , and one woman had four follicles in group 1 , while in group 2 14 women had one follicle and only 3 women had two follicles . the mean numbers of follicles were 1.89  0.9 and 1.18  0.393 in group 1 and group 2 , respectively . the mean follicular diameter ( 20.67  0.970 mm vs.20.76  0.903 mm ) was similar in group 1 and group 2 , respectively [ table 2 ] . the mean endometrial thickness in group 1 ( 7.47  1.223 mm ) and group 2 ( 8.56  1.375 mm ) was not statistically different [ table 2 ] . pg / ml ) was significantly higher than group 2 ( 291.82  59.86 pg / ml ) [ table 2 ] . most common treatable cause of infertility is anovulation . for last 40 years , the first line of treatment for women having anovulatory infertility was clomiphene citrate . unfortunately , despite high rates of ovulation , pregnancy rates per cycle remain relatively low . both thin endometrium and non - trilaminar pattern of the endometrium at midcycle are associated with low pregnancy rates and early pregnancy loss . for women who experienced these adverse effects with clomiphene citrate , the next optionis induction of ovulation with gonadotropin which increases both cost and risk to the woman . alternatively , letrozole a potent aromatase inhibitor with excellent oral bioavailability and relatively short half - life is used for ovulation induction . in our study , both the groups were comparable with respect to age and body mass index . although previous studies reported similar ovulation rate by clomiphene citrate and/or letrozole , we observed higher ovulation rate in the clomiphene citrate group compared with letrozole - treated group . however , our results are compared to previous study reporting monofollicular development with letrozole . nevertheless , we observed similarity in mean follicular diameter between the two groups which is concurrent to previous report . effect of clomiphene and letrozole on endometrium in ourstudy was comparable with study by mitwally et al . , who noted that women who had endometrial thickness of 5 mm with clomiphene citrate responded well with 2.5 mg of letrozole and showed an increase in endometrial thickness up to 8 mm . contrary to this , fisher et al . , and kar observed no difference of endometrial thickness in their study . estimation of serum estradiol is important especially to know the quality of ovum , and for administration of human gonadotrophin ( hcg ) in cases of stimulated cycle . although human gonadotrophin was not used in our study , we estimate serum estradiol to know the antiestrogenic property of clomiphene citrate and letrozole . concurrent to previous reports we observed a significantly higher serum estradiol levels in clomiphene citrate - treated group . although the numbers of follicles developed per cycle by using clomiphene citrate was higher ; nevertheless , it increases the chances of ovarian hyperstimulation syndrome and multiple pregnancy . interestingly , kar also showed monofolliculogenesis similar to our study ; however , the pregnancy rate was higher in letrozole group in contrast to clomiphene group . this result may be due to increase resistance to the clomiphene in polycystic ovarian syndrome ( pcos ) . in contrast , our study response to the clomiphene was good as none of our cases were pcos . on the basis of our study we conclude that clomiphene citrate should be considered as first line of drug and failing which letrozole may be tried as alternative . we acknowledge small sample size as limitation of our study and warrant future studies with larger sample size to the compare the efficacy of clomiphene citrate and letrozole .
background : letrazole is an aromatase inhibitor , which is useful in ovulation induction . however , evidence on its efficacy over clomiphene citrate , which is the first of drug used for therapy of anovulation , is insufficient in indian patients.aims:to compare the efficacy of letrozole and clomiphene citrate in attaining optimal follicular growth.materials and methods : the study was conducted in the infertility clinic of mahatma gandhi medical college and research institute , pondicherry , india from june 2008 to december 2009 . 
 fifty women with ovulatory dysfunction as a cause of infertility were enrolled and randomized into two groups of 25 each . 
 group 1 received clomiphene citrate in incremental dose from 50 mg up to150 mg and group 2 patient received letrozole in incremental dose from 2.5 mg to 7.5 mg , depending upon the ovulation response . in both the groups , number of follicles , diameter of large follicle , endometrial thickness , and serum estradiol and pregnancy rate were compared . 
 the data from both groups are represented as mean and standard deviation and statistically compared using student 's t test.results:the number of follicles ( 1.89  0.9 vs 1.18  0.393 ) and serum estradiol levels ( 437.5  293.7 pg / ml vs 291.82  59.86 
 pg / ml ) were higher in group 1 , while follicular diameter ( 20.67  0.970 mm vs. 20.76  0.903 mm ) and endometrial thickness ( 8.5 mm vs.7.4 mm ) were similar in both the groups.conclusions:although letrozole is used for ovulation induction in anovulatory infertility , no significant beneficial effects of letrozole compared to use of clomiphene citratewere observedin ourstudy . 
 hence , we concur with the use of clomiphene citrate as the first line of drug for ovulation induction in indian population and warrant larger size studiesto further validate our results .