**2. Pathophysiology of luteal phase in ART**

Progesterone and estrogen are required to prepare the uterus for embryo implantation and to modulate the endometrium during the early stages of pregnancy. In the normal luteal phase of a nonpregnant woman, steroid production peaks four days after ovulation and continues for one week until falling several days before the next menses. If pregnancy occurs, progesterone production is restored by human chorionic gonadotrophin (hCG) stimulation. Once the oocyte is released, the follicle collapses and the remaining granulosa cells, which have acquired receptors for luteinizing hormone (LH), rapidly undergo luteinisation under the influence of LH. The formed corpus luteum requires regular

© 2012 Ghanem and Al-Boghdady, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 Ghanem and Al-Boghdady, licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

stimulation by LH to maintain adequate production of progesterone [2].The absence of LH due to pituitary suppression by gonadotropin releasing hormone (GnRh) analogues deprives the corpus luteum from this LH.

Luteal Phase Support in ART: An Update 157

**3. Options of luteal support in ART** 

route is the preferred way to administer natural progesterone.

recommended in more recent studies.

**4. Progesterone** 

To correct the luteal phase defect in stimulated IVF/ICSI cycles, progesterone and /or human chorionic gonadotrophin (hCG) can be administered. The addition of estardiol to progesterone luteal support is currently debated and the final situation in luteal phase support needs further studies. The use of GnRh agonist in luteal support has been

Progesterone produced by the corpus luteum causes the secretory transformation of the endometrium that is necessary for implantation and for the early development of the fertilized ovum. In response to progesterone, the glands become tortuous and secretory and there is an increase in stromal vascularity, thus making the endometrium both morphologically and functionally well prepared for implantation. Progesterone preparations can be divided into two groups: natural progesterone and synthetic preparations. Synthetic derivatives or progestins are 1) 17-hydroxyprogesterone derivatives and 2) 19-nortestosterone derivatives. The 19-nortestosterone synthetic derivatives resist enzymatic degradation if given orally, but have a high incidence of secondary effects and have been associated with mood changes, depression, virilization, decreases in high-density lipoproteins, luteolysis and a possibly teratogenic effect that limits their use during fertile cycles. Natural progesterone has no adverse effects on high-density lipoproteins, no teratogenic effects and is more effective than the derivatives in inducing secretory changes at the endometrium (22). Traditionally, progesterone was given by means of intramuscular injections, what makes it unacceptable for long-term treatment. In this respect the vaginal

Various formulations of progesterone are now available, including oral, vaginal, and intramuscular (I.M) progesterone . Parenteral administration of progesterone, vaginally or I.M, does not subject the compound to the significant metabolic consequences of oral administration. Progesterone administered orally is subjected to first-pass pre-hepatic and hepatic metabolism. This metabolic activity results in progesterone degradation to its 5αand 5β-reduced metabolites [23] . Levine and Watson [24] compared the pharmacokinetics of an oral micronized progesterone preparation (Prome- trium, 100 mg, Solvay Pharmaceuticals Inc., Marietta, GA) with that of a vaginal progesterone gel (Crinone 8%, 90 mg).Results showed that the vaginal gel was associated with a higher maximum serum concentration of progesterone. Furthermore, the 24-hour area under the curve for drug concentration vs. time (AUC0–24) was higher in the group that had received the vaginal preparation. This signies greater total progesterone exposure over 24 hours for a single dose of progesterone administered in a vaginal gel compared with a similar dose administered orally. Levine and Watson [24] concluded that the vaginal administration of progesterone results in a greater bioavailability with less relative variability than oral progesterone. There are no agreement on the standard dose of progesterone in luteal phase support. Studies have been conducted using I.M. injections

In the mid-1980s, the incorporation of GnRh agonists into ovarian stimulation regimens became associated with improved outcomes after IVF and other assisted reproduction technologies. Pituitary function does not resume completely until 2–3 weeks after the end of GnRH-agonist therapy; and luteal phase support was considered essential to counter any luteal insufficiency that may have a negative impact on an early pregnancy [3 ,4]. It is well established that luteal function is compromised in IVF cycles [5, 6, 7]. The reasons for luteal phase abnormalities in ART are multiple. It has been shown that the function of the corpus luteum is compromised by the process of follicular aspiration for oocyte retrieval as granulosa cells are mechanically disrupted and aspirated. The severity of the disruption seems to be in relation to the vigorousness and the number of aspirations and therefore the number of granulosa cells that are dislodged from the membrana granulosa layer [8].It has been proved that luteal phase defect occurs in long GnRh-agonist protocol [9] and that corpus luteum deficiency as sequel of assisted reproduction techniques in general , is partially caused by aspiration of the granulosa cells and the use of gonadotropin-releasing hormone agonists. Due to the immediate recovery of pituitary gonadotrophin release just after discontinuation of the GnRH antagonists, it has been hypothesized that the luteal phase would be less disturbed in these cycles [10]. Although preliminary observations in intrauterine insemination cycles favored this contention, studies on a limited number of cases undergoing IVF demonstrated that there was a significant reduction in pregnancy rates without luteal phase support [11]. The serum LH levels in the early and midluteal phase of GnRH antagonist–treated cycles were low, regardless of the regimen used to induce oocyte maturation [12]. In the absence of luteal phase support, the area under the curve for progesterone was suboptimal and this was accompanied by premature luteolysis [13]. In nonsupported cycles, the length of the luteal phase was shortened and early bleeding occurred [14]. Based on this body of evidence, luteal phase support should be considered in IVF cycles where GnRH antagonists are used.

Other causes of the luteal phase defect observed in stimulated IVF cycles are related to the multifollicular development achieved during ovarian stimulation. This leads to supraphysiological concentrations of steroids secreted by a high number of corpora lutea during the early luteal phase, which directly inhibit LH release via negative feedback actions at the hypothalamic–pituitary axis level, rather than a central pituitary cause or steroidogenic abnormality in the corpus luteum [15].As previously alluded to, luteal phase defect in IVF is present whether GnRH agonist or antagonist is used [16]. Many meta-analyses concurred that luteal support improves IVF outcome [17, 18 ,19 ,20, 21].The most recent Cochraine review [21] confirmed earlier studies and found that luteal phase support with hCG provided signicant benet as compared to placebo or no treatment, with a signicant increase in ongoing pregnancy rate and a decrease in miscarriage rate when GnRH agonist was used. Luteal phase support with progesterone, compared to placebo or no treatment in GnRH agonist and non-GnRH agonist cycles, also resulted in a signicant increase in clinical pregnancy rates and live birth.
