Nowadays, adenomyosis is frequently encountered in women undergoing IVF [12]. The use of GnRH-a treatment for adenomyosis and its effect on fertility are debatable. In the present study, GnRH-a treatment had different effects on pregnancy outcomes because of different therapeutic responses in patients with enlarged adenomyosis. The group more responsive to GnRH-a (GN group) was shown to be associated with increased clinical pregnancy rate, ongoing pregnancy rate, and live birth rate and lower late miscarriage rate compared with the less responsive group (GL group). The implantation rate was also higher in the more responsive group (GN group) than in the less responsive group (GL group), although the difference did not reach statistical significance.
Some studies [4, 5] reported that pretreatment with GnRH-a has no benefit in improving IVF outcomes in adenomyosis. Notably, these studies focused on fresh embryo transfer cycles. The hyperestrogenic state resulting from subsequent controlled ovarian stimulation (COS) may diminish the effect of GnRH-a and even aggravate adenomyosis. Furthermore, women with adenomyosis are often in their later reproductive years and have inherently reduced ovarian reserves. Ovarian suppression with a multi-dose GnRH-a may negate its effect on the ovarian response, which might be an additional cause of impaired treatment efficacy. Therefore, IVF with FET may be preferable in these patients. The association between pretreatment with a GnRH-a and pregnancy outcomes in FET cycles may not be affected by ovarian stimulation regimens. Moreover, treatment with GnRH-a during FET cycles does not affect the dose of gonadotropin or the duration of COS. Recently, a few studies have demonstrated the positive effect of long-term GnRH-a administration before FET on the pregnancy outcomes of infertile women with adenomyosis and a normal sized uterus. In a study by Niu et al. [13], clinical pregnancy, implantation, and ongoing pregnancy rates were significantly higher in women who were pretreated with GnRH-a than in those who were not. Hebisha et al. [14] reported a significant increase in the implantation and pregnancy rates when GnRH-a was administered prior to estrogen–progesterone preparation of the endometrium in FET compared to when it was not. These studies indicate some beneficial effects of GnRH-a therapy in women with adenomyosis, including a potential for improved implantation. Our study extends these findings to demonstrate that this effect of GnRH-a administration is more pronounced in patients undergoing FET who achieve a normal-size uterus after GnRH-a pretreatment than in those with an enlarged uterus even after GnRH-a pretreatment.
The adenomyotic uterus provides a dysfunctional environment for the maintenance of pregnancy [2, 15]. Mechanisms may include uterine dysperistalsis, abnormal concentrations of free radicals in the uterine environment, and altered endometrial vascularization. All the factors would otherwise be in direct contact with invading trophoblast cells [16–19]. Evidence has confirmed that GnRH-a promotes a decrease in the size and demarcation of adenomyotic lesions in the uterus [20, 21]. The pathomechanism of GnRH-a therapy on adenomyosis is multifactorial and is suggested to involve a hypo-estrogenic effect, which reduces angiogenesis, inhibits cell proliferation, induces apoptosis, and decreases vascular endothelial growth factor (VEGF) secretion in the myometrium [22–24]. Additionally, a previous study using a mouse model of adenomyosis revealed that GnRH-a treatment might improve pregnancy outcomes by restoring endometrial receptivity [25]. Our results suggest that the reduction in uterine size in response to GnRH-a administration increases the probability of live birth in adenomyosis patients undergoing IVF with FET. It is theoretically possible that the greater reduction in uterine size after GnRH-a use may relate to increased medical responsiveness. Moreover, the ultra-long downregulation has been demonstrated to reduce early pregnancy loss in the setting of adenomyosis. We found that the uterine volume after GnRH-a treatment may account for late miscarriage owing to anatomical and hormonal factors.
It is worth noting that 23% of patients still had an enlarged uterus after adequate doses of GnRH-a, and the live birth rates of these patients were relatively low in our study. A possible explanation for this observation is that GnRH-a has a weaker anti-proliferative effect on adenomyosis cells in these patients. Our results are supported by the study by Khan et al. [26], who found that GnRH-a did not affect cell growth in 30% of women with adenomyosis and observed a lower cellular response to GnRH-a in adenomyosis cells than in cells derived from endometriosis and fibroids. This suggests that other pretreatment options, such as surgery, should be considered when GnRH-a administration is not satisfactory. The cut-off value selected on the ROC curve of uterus volume after GnRH-a treatment for detecting live birth was 144.7.
Our study demonstrated that adenomyosis patients in the GN group had a significantly higher BMI than those in the GL group. Overweight patients with enlarged adenomyosis may have poorer pregnancy outcomes. While earlier studies have concluded that obesity is closely correlated with the development of adenomyosis [2], our finding extends these claims by indicating that high BMI may be a risk factor for less responsiveness to GnRH-a treatment for enlarged adenomyosis. [27] This may be because estradiol levels arising from the peripheral adipose tissue negated the desired hypoestrogenic effect of GnRH-a administration. These results are potentially useful for pre-IVF counseling of women with adenomyosis and uterine enlargement.
The main strength of this study is the inclusion of a study population that was strictly limited to enlarged adenomyosis patients. The globular enlargement of the uterus is the most common feature of adenomyosis, which can be easily identified clinically and sonographically. And primary outcome and only the results regarding the first cycle should be considered. Thus, strict selection criteria reduced the heterogeneity of the study population. Moreover, the study was restricted to FET, which is an important area that deserves more research. Finally, multivariable logistic regression models were used to control for potential confounders.
Nevertheless, this study also has some limitations. First, this was a retrospective study. Second, as this study included patients who wanted to become pregnant, histological confirmation of adenomyosis was not possible. Nonetheless, we do not think that this significantly affected our results as TVS is an accepted and accurate noninvasive method for diagnosing adenomyosis. TVS has been demonstrated to have a sufficiently high diagnostic accuracy in adenomyosis cases, with a reported sensitivity of 82.5% and a specificity of 84.6% [10]. Moreover, TVS is a cost-effective, less invasive, and readily available tool for obstetricians and gynecologists. Uterine size is routinely measured during ultrasound examination, and the ultrasonographic features of adenomyosis have been clearly defined. Third, there was no control group of patients with adenomyosis and an enlarged uterus who were not pretreated with GnRH-a. However, this would not have been ethical given the strong evidence favoring long-term GnRH-a use.
In conclusion, we found that GnRH-a administration before FET for adenomyosis could be an effective treatment option for adenomyosis patients with uterine enlargement whose lesions are GnRH-a-susceptible. However, approximately a quarter of adenomyosis patients with an enlarged uterus may be less responsive to GnRH-a, especially overweight women. When the reduction of uterine size after treatment is not obvious, other treatment methods should be considered. A subsequent prospective randomized controlled study is required to provide conclusive evidence of the benefit of this approach.