Endometrial receptivity and Endometrial Thickness are crucial during IVF Cycles

The endometrium or uterine lining is important to reproduction since the embryo must implant into the endometrium of the uterus to initiate a pregnancy.  Prior to an IVF attempt, it is important to ensure that the uterine cavity is normal.  This can be done using many different techniques.  The most accurate ways to evaluate the uterine cavity are via saline sonohysterogram (saline vaginal ultrasound) or hysteroscopy (surgical evaluation of the uterine cavity).

During an IVF attempt the uterine cavity is evaluated to ensure that proper development of the lining occurs.   Studies suggest that a uterine lining thickness of 6 mm or less results in fewer pregnancies.  Therefore, most providers would prefer to have a uterine lining of at least an 8 mm.  Likewise, the sonographic pattern of the uterine lining is evaluated by ultrasound multiple times during the IVF cycle.   A tri-laminar or triple line pattern on ultrasound is suggestive of a uterine lining that has developed appropriately in response to increasing estrogen levels during the IVF cycle.

Unfortunately, not all patients achieve an adequate uterine lining thickness or tri-laminar pattern.  This has lead many providers to look for ways to improve the appearance of the uterine lining with adjuvant therapies.

Many adjuvant therapies are used empirically to enhance cycle outcome during assisted reproductive technology cycles. However, there are little data to validate this practice.  Not uncommonly during assisted reproduction procedures, practitioners encounter patients who demonstrate sonographic evidence of endometrial insufficiency with an endometrial thickness less than 8 mm on the day of human chorionic gonadotrophin (HCG) administration.  While some researchers have found that endometrial thickness has minimal impact on pregnancy outcome, most studies agree that endometrial thickness affects pregnancy outcome in patients undergoing assisted reproduction.  While many empirical therapies are used with the hope of enhancing endometrial thickness and optimizing pregnancy outcome, few studies have evaluated the efficacy of these treatments .

Sildenafil (Viagra) is a type 5-specific phosphodiesterase inhibitor that augments the vasodilatory effects of nitric oxide on vascular smooth muscle by preventing the degradation of cyclic guanyl monophosphate.  Studies suggest that sildenafil may augment uterine blood flow leading to an enhanced endometrial lining response and ultimately improved pregnancy rates.

Vaginal estradiol has been used to augment the estrogen effect on the uterus necessary for uterine receptivity; however, its clinical efficacy has not been proven in the literature.   Compared with oral administration, vaginal estradiol has been shown to induce 10-fold higher serum and 70-fold higher endometrial concentrations.

Low-dose (81 mg) aspirin is used by many assisted reproduction programs. While a few studies have demonstrated efficacy with low-dose aspirin, its value is still uncertain.

These and other adjuvant therapies have been used in an attempt to improve endometrial receptivity for patients.  Unfortunately, to date no one single therapy has been proven to be effective for all patients.   Providers must evaluate each patient individually and use their best judgement as to which adjuvant therapy may benefit that specific patient.

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