Modifications in uterine and intraovarian artery impedance in cycles of treatment with exogenous gonadotropins: effects of luteal phase support

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1 FERTILITY AND STERILITY Vol. 64, No.1, July 1995 Copyright 1995 American Society for Reproductive Medicine Printed on acid-free paper in U. S. A. Modifications in uterine and intraovarian artery impedance in cycles of treatment with exogenous gonadotropins: effects of luteal phase support Francesca A.L. Strigini, M.D.* Patrizia A. M. Scida, M.D. Cristiana Parri, M.D. Alessandra Visconti, M.D. Sabrina Susini, B.D. Andrea R. Genazzani, M.D. Department of Gynecology and Obstetrics, University of Pisa, Pisa, Italy Objective: To determine the effects of induction of multiple ovulation and ofluteal P supplementation on the impedance to blood flow in the uterine and intraovarian arteries during the luteal phase. Design: A prospective study using transvaginal color flow Doppler imaging. Setting: A university-based infertility center. Patients: Fifty-six women with unexplained or male factor-related infertility undergoing lui. Interventions: The patients were studied either during spontaneous cycles (n = 16) or in cycles of induction of multiple follicular development with purified FSH (n = 40). In 18 treated cycles, the luteal phase was supplemented with natural P. Main Outcome Measures: The pulsatility index was recorded from uterine and intraovarian arteries on the day ofe2 peak and 5 and 10 days thereafter. On the same days, E2 and P plasma levels were measured by RIA. Results: The intraovarian pulsatility index was significantly lower in FSH-treated than in spontaneous cycles on the day of E2 peak. Also, the uterine pulsatility index was significantly lower in treated cycles than in spontaneous cycles on the day of E2 peak and 5 days thereafter. In the late luteal phase, P supplementation was correlated with a significant decrease in uterine pulsatility index as compared with both spontaneous cycles and FSH-treated cycles without luteal support. Conclusions: Multiple follicular development is associated with a significant reduction in the impedance to perifollicular blood flow. Progesterone, as well as E2, seems able to decrease the impedance to blood flow in uterine arteries in women. Fertil Steril 1995; 64:76-80 Key Words: Color flow Doppler imaging, ovulation induction, luteal phase support, uterine artery, intraovarian arteries In reproductive organs, neoangiogenesis physiologically occurs around the time of ovulation and during trophoblastic invasion (1). On the other hand, sexual steroids can modify the blood flow in pelvic vessels (2-4). These phenomena could not be evaluated in women until the association of pulsed Doppler and gray-scale ultrasound imaging offered a noninvasive method for the study of blood flow to the reproductive organs (5). Subsequently, the development of transvaginal probes and color flow imaging Received July 15, 1994; revised and accepted January 25, * Reprint requests: Francesca A. L. Strigini, M.D., Istituto di Clinica Ginecologica ed Ostetrica, Universita' degli Studi di Pisa, Via Roma 67, I Pisa, Italy (FAX: ). greatly facilitated the visualization and the measurements of flow parameters from small pelvic vessels (6). Many studies aimed at evaluating modifications in impedance to blood flow in ovarian vessels and in uterine arteries throughout spontaneous and induced menstrual cycles. Especially in gonadotropintreated cycles, the observations often were limited to the follicular and the early luteal phase, corresponding to the period in which patients usually are treated actively (7-9). However, it has been suggested repeatedly that the luteal phase of gonadotropin-treated cycles is different from that of spontaneous cycles, at least with respect to ovarian steroidogenesis and endometrial histology (10, 11). 76 Strigini et al. Uterine and intraovarian artery impedance Fertility and Sterility

2 Consequently, luteal support is used in these cycles with the aim of ameliorating the uterine environment, thus increasing the pregnancy rates in treated patients (12). The present study thus focused on evaluating whether induction of multiple follicular development, with and without P supplementation, is related to modifications in the impedance to blood flow in uterine and intraovarian arteries throughout the luteal phase of the cycle. MATERIALS AND METHODS The study group consisted of 56 normally cycling women affected by primary infertility (mean duration 3.7 years; range 2 to 10 years): 16 women were studied throughout spontaneous cycles monitored during the infertility workup and 40 women were studied in stimulated ovarian cycles followed by lui (for male factor-related or unexplained infertility). The mean age of these women was 33.5 years (range 25 to 43 years). Menstrual cycle abnormalities were excluded in all patients with FSH, LH, and PRL plasma assay in the early follicular phase and P assay throughout the luteal phase. Abnormalities of the female genital t~act were excluded by ultrasonography, hysterosalpl~gogram, hysteroscopy, or laparoscopy, as appropriate. None of the women had received any form of hormonal therapy during the preceding 6 months, and none was taking vasoactive drugs. In the 40 treated cycles, multiple follicular development was induced with purified FSH (Metrodin; Serono, Rome, Italy) starting on day 3 of the cycle at the dose of 225 IU/d 1M. Plasma E2 assay and transvaginal ultrasonography were performed every other day, and the dose of FSH was adjusted according to these parameters. The ovulation was induced with 10,000 IU 1M hcg (Profasi HP; Serono) when the mean diameter of the largest follicle was ~20 mm and serum E2 concentrations were ~800 pg/ml (conversion factor to SI units, 3.671). In 18 patients the luteal phase was supported with 100 mg 1M P supplementation (Gestone; A.M.S.A., Barberino di Mugello, Italy) on days 7, 9, 11, and 13 after the E2 peak. In spontaneous cycles, the follicular phase was monitored with E2 assay and sonography similarly to the induced cycles. Mter informed consent was obtained, velocity waveforms from uterine and intraovarian arteries were recorded from all patients on days 0, 5 (early luteal phase), and 10 (late luteal phase) after the E2 peak. A sample of peripheral venous blood was taken on the same days of each scan for the measurement of serum E2 and P by RIA, which was performed Vol. 64, No.1, July 1995 Figure 1. Transvaginal color flow Doppler sonography showing the ascendmg branch of the left uterine artery. The white mark indicates ~he placemen~ of th.e Doppler gate; the corresponding flow velocity waveform IS depicted on the right. with commercial materials (Coat-A-Count Estradiol Diagnostic Products Corporation, Los Angeles, CA and Prog-CTK-2; Sorin Biomedica, Saluggia, Italy, respectively). The scanner used for the study (AU 590; Hitachi ESAOTE Biomedica, Genova, Italy) was equipped with an endovaginal probe producing a 6.5-MHz beam for imaging, and a 5-MHz pulsed color Doppler system for blood flow analysis. Wall filters (100 Hz) were used to eliminate low-frequency signal occurring from noise. The morphology of the uterus and the adnexa was explored by B-mode sonography. Color Doppler enabled us to visualize uterine and intraovarian flow to obtain flow velocity waveforms. The right and th~ left ascending branches of the uterine arteries were imaged lateral to the internal cervical os in coronal planes (Fig. 1). The colored intraovarian arterial flow was identified in the substance of the ovary next to a preovulatory follicle or corpus luteum (Fig. 2). The angle of insonation was changed to obtain maximal color intensity and maximum waveform amplitude and clarity. The pulsatility index was calculated automatically on both uterine and intraovarian arteries (13). The mean pulsatility index of the left and the right uterine arteries was calculated and used for the statistical analysis. The velocity waveforms with the lowest recorded pulsatility index were selected for analysis of intraovarian flow. The results are reported as mean ± SEM. The statistical analysis of the results was performed with the Student's t-test and two-way analysis of variance, as appropriate. RESULTS As expected, in FSH -stimulated cycles, E2 plasma levels were significantly higher (P < ) than in Strigini et al. Uterine and intraovarian artery impedance 77

3 Figure 2 Transvaginal color flow Doppler sonography of the vascular ring surrounding a corpus luteum obtained 5 days after hcg administration. The white mark shows the placement of the Doppler gate; the corresponding flow velocity waveform is depicted on the right. spontaneous cycles both before and after hcg administration (E 2 peak: 858 ± 92 versus 247 ± 18 pg/ ml; day 5: 556 ± 74 versus 115 ± 13 pg/ml; day 10: 395 ± 49 versus 102 ± 9 pg/ml). No significant difference in P concentrations was observed on the day of E2 peak (0.5 ± 0.1 versus 0.4 ± 0.1 ng/ml; conversion factor to SI units, 3.180). On day 5 after the E2 peak, the P plasma levels were significantly higher than in spontaneous cycles (36.7 ± 4.2 versus 10.4 ± 0.9 ng/ml, P < ), but this increase was not maintained on day 10 (16.4 ± 3.9 versus 7.7 ± 1.1 ng/ml) unless exogenous P was administered (38.7 ± 4.0 ng/ml). In spontaneous cycles the pulsatility index of intraovarian arteries showed a significant decrease on day 5 after the E2 peak compared with the preovulatory values (0.81 ± 0.07 versus 1.03 ± 0.11, P < 0.01). No further modification was observed in the late luteal phase (pulsatility index: 0.85 ± 0.07). In the treated cycles, the pulsatility index ofintraovarian arteries at E2 peak (0.81 ± 0.04) was significantly lower than the pulsatility index in spontaneous cycles (P < 0.02), but it did not show any significant change after ovulation (day 5: 0.74 ± 0.03; day 10: 0.85 ± 0.06). Moreover, at each test point of the luteal phase, the pulsatility index of the intraovarian arteries was not significantly different in treated and in spontaneous cycles. As expected, P supplementation did not modify intraovarian pulsatility index (0.87 ± 0.06 versus 0.81 ± 0.07). A significant decrease (P < 0.05) in the mean pulsatility index of uterine arteries was observed throughout the luteal phase. The mean uterine artery pulsatility index also was significantly lower (P 78 Strigini et al. Uterine and intraovarian artery impedance < 0.05) in stimulated than in spontaneous cycles both at E2 peak (2.02 ± 0.16 versus 2.47 ± 0.24) and in the early luteal phase (1.95 ± 0.09 versus 2.31 ± 0.08). However, in the late luteal phase, the pulsatility index values were similar in the spontaneous (2.07 ± 0.13) and FSH-induced cycles without P administration (2.10 ± 0.12), whereas they were significantly lower (P < 0.01) in stimulated cycles in which exogenous P was administered (1.68 ± 0.07). In fact, in cycles with a supplemented luteal phase, the uterine pulsatility index showed a further significant decrease on day 10 compared with day 5 after E2 peak (1.68 ± 0.07 versus 1.97 ± 0.12, P < 0.005), whereas this decrease was not observed in treated cycles without P administration (2.10 ± 0.12 versus 1.91 ± 0.10). Four pregnancies were obtained out of the 40 treated cycles; one patient, in whom the luteal phase was not supplemented, aborted spontaneously at 7 weeks, whereas the other three pregnancies (one with and two without luteal phase support) are ongoing. In the late luteal phase of conception cycles, uterine pulsatility index was 1.84 ± 0.39 (range 1.42 to 2.18) for successful pregnancies and 2.46 in the patient who aborted. DISCUSSION The above data suggest that the induction of multiple follicular development is able to decrease the impedance to blood flow in both uterine and intraovarian arteries. Moreover, luteal supplementation with exogenous P can induce a further reduction in impedance to uterine blood flow. It has been shown repeatedly that the impedance to ovarian blood flow is lower in the luteal phase than in the follicular phase (5, 14, 15). The modifications of perifollicular blood flow seem to precede ovulation (16). A similar pattern also has been described in IVF-ET cycles after exogenous gonadotropin stimulation (7, 17). Some authors (18) could not detect any difference between the values of the resistance index in spontaneous and stimulated cycles, but most of their patients were treated with clomiphene citrate, which might affect ovarian vascularization differently from exogenous gonadotropins. In gonadotropin-treated cycles, lower pulsatility index values have been observed in patients with high endocrine response (7), and pulsatility index values were correlated inversely with the number of follicles and E2 plasma levels (17). Therefore, in cycles of induction of multiple follicular development, it could be expected that the preovulatory intraovarian pulsatility index was lower than that of spontaneous monofollicular cycles. It is unknown whether the preovulatory Fertility and Sterility

4 reduction of intraovarian pulsatility index in FSHtreated cycles is related to the increased number of preovulatory follicles or it is mediated by the increase of E2 or other substances induced by FSH. The subsequent lack of significant differences in intraovarian pulsatility index between spontaneous and FSH-treated cycles throughout the luteal phase may be related to the shorter life span of the corpus luteum in gonadotropin-treated cycles (10). This may hold true independent of the functional relationship between luteal blood flow and steroidogenesis. The modifications observed in uterine impedance during the luteal phase of FSH-treated cycles may be relevant in the treatment of infertile couples. The pattern we observed in spontaneous cycles is similar to that described by some authors using the transvaginal approach (19). The observation that uterine pulsatility index during stimulated cycles, both before and after ovulation, is reduced significantly as compared with spontaneous cycles may be explained by the increase in plasma E2 levels. The effects of estrogens on the vascular bed is well documented both in animals and in humans. The administration of estrogens to the ewe induces a dose-dependent increase in blood flow in the uterine arteries (2, 3). In the human, the administration of estrogens to postmenopausal women (20, 21), patients with premature ovarian failure (22), or cycling infertile women (23) induces a decrease of the vascular resistance of uterine arteries. Moreover, discontinuity in estrogen synthesis caused by gonadorelin-analogue therapy is responsible for an increased vascular impedance in the uterine arteries (24). However, the hypothesis that uterine impedance to blood flow is regulated mainly by plasma E2 cannot account for the decrease observed in the luteal phase of both spontaneous and induced cycles when E2 plasma levels are significantly lower than those from the day before ovulation. In the ewe, the administration' of P is able to counteract the effect of estrogens on uterine arteries (2, 4). In postmenopausal women on hormone replacement therapy, Hillard et al. (20) showed a significant increase in uterine pulsatility index when either norethindrone acetate or medroxyprogesterone acetate were added to transdermal E 2; however, other studies failed to detect significant modifications of uterine pulsatility index during combined estrogen-progestogen treatment as compared with estrogen-only treatment (21, 22). The present study seems to demonstrate that P not only does not reduce uterine blood flow in women, but it actually reduces uterine impedance. In fact, the administration of exogenous P in the late luteal phase of stimulated cycles, with the consequent sig- nificant increase in P plasma levels, was related to a decrease in uterine pulsatility index to levels significantly lower than those from both spontaneous cycles and FSH-treated cycles without P supplementation. Possible explanations for the fact that this effect was not observed in previous studies may be related to the use of different progestogens, at variable dosages or with different routes of administration. It has been suggested that an increased impedance to blood flow may be regarded as a possible cause of infertility (23, 25) and that a decrease in uterine artery pulsatility index is related to an improved probability of conception (8, 9, 23). Luteal phase support currently is used in cycles of induction of multiple follicular development (12). 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