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ASRM 2016: New Study Examines Lining Thickness and Its Impact on Letrozole with IUI Pregnancy Rates

This year at the American Society of Reproductive Medicine’s 2016 Scientific Congress and Expo in Salt Lake City, October 15 to 19, the physician-scientists at Shady Grove Fertility presented the findings from 17 studies. One study that has provided significant insight into low-tech or basic infertility treatment is a study of the use of a medication called letrozole with IUI. 

Letrozole Used for Ovulation Induction

For many patients, low-tech options are their first step when undergoing fertility treatment. Historically these patients are placed on an oral medication called clomiphene citrate (Clomid) to induce or augment ovulation. More recently, letrozole has entered as a frequently used alternative for ovulation induction. Once the recruitment and development of mature-sized follicle(s) is confirmed, timed intercourse +/-intrauterine insemination (IUI) is undertaken in the hopes of conception. While there are many factors that can impact the outcome of treatment for patients, one considered to be important has been the thickness of the endometrial lining.

How Does Lining Thickness Affect Letrozole with IUI Pregnancy Rates?

The belief has always been that a thicker lining is more favorable for implantation and pregnancy. “Recent data have been mixed as to whether lining thickness in clomiphene citrate cycles determines chances of pregnancy,” explains Kate Devine, M.D., Co-director of Research at Shady Grove Fertility and a practicing board certified reproductive endocrinologist in SGF’s K Street, Washington, D.C. location. “Therefore, in the current study, we decided to correlate endometrial thickness with outcomes.”

Thinning of the endometrial lining is frequently seen in Clomid cycles. “When this occurs, patients may be prescribed another oral medication called letrozole in their next treatment cycle instead of Clomid,” says Dr. Devine. Letrozole acts in a similar way to Clomid—to induce ovulation—and is thought to have less of a negative effect on endometrial thickness.

Is Thicker Really Better for Patients Using Letrozole with IUI?

This year at the ASRM Scientific Congress & Expo, the physicians at Shady Grove Fertility presented a poster titled “Factors impacting endometrial thickness (EMT) and outcomes in letrozole intrauterine insemination (IUI) cycles.” The study retrospectively looked at 533 IUI cycles from 2014 to 2015 where letrozole was used alone or in conjunction with gonadotropins (injectable medications used to induce ovulation). The purpose of the study was to determine the correlation between endometrial thickness and pregnancy rates. In other words, is thicker really better for patients using letrozole with IUI?

This study found that, yes, lining matters, but once a patient’s lining reaches 5 mms the chance of pregnancy didn’t improve significantly as the lining got thicker. Women with a 5 mm thick lining were found to have a 17 percent clinical pregnancy rate while those with lining measuring at 9mm had the same clinical pregnancy rate. “While the thicker is better theory did not hold for this study population undergoing letrozole cycles, we did find two other factors that significantly impacted cycle outcomes: the number of follicles and the total motile sperm count at the time of insemination,” explains Dr. Devine.

What This Means for Patients

The take away for patients is simple. The thickness of the endometrial lining is important but the bar of what is considered adequate may be lower (and more obtainable). Of the 533 cycles that were analyzed very few fell into the under 5 mm category.

About the 2016 ASRM Scientific Congress & Expo
The 2016 ASRM Scientific Congress & Expo is the premier scientific congress for reproductive medicine that will address state-of-the-art issues in reproductive medicine and science. Held from October 15 to 19, 2016, in Salt Lake City, UT, the theme of the 2016 Scientific Congress of the American Society for Reproductive Medicine is “Scaling New Heights in Reproductive Medicine.”  The program features scientific, postgraduate, and video presentations as well as plenary lectures addressing the most pressing clinical and basic-science issues in reproductive medicine.


To learn more about using letrozole with IUI or to schedule an appointment, please contact our New Patient Center at 1-877-971-7755. 


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