1 Academic Department of Obstetrics and Gynaecology and 2 Department of Biological Sciences, University of Hull, Cottingham Road and 3 The Hull IVF Unit, Princess Royal Hospital, Saltshouse Road, Hull, UK
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Abstract |
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Key words: embryo transfer/junctional zone contractions/tenaculum/transvaginal ultrasound
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Introduction |
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Embryo transfer is one of the most critical steps affecting the success rate of in-vitro fertilization (IVF) and has changed little since IVF was first described. While there is general agreement that a smooth embryo transfer is associated more frequently with successful outcome (Wood et al., 1985; Mansour et al., 1990
; Visser et al., 1993
; Tomas et al., 1998
), this opinion is not unanimous (Nabi et al., 1997
; Tur-Kaspa et al., 1998
). There is also no consensus about how an embryo transfer can be classified as an easy or difficult procedure. The importance of several variables associated with embryo transfer has been recently recognized (Kovacs, 1999
). A correction of uterine position, by applying traction to the cervix with a tenaculum, is a procedure sometimes used prior to embryo transfer. The aim of this study was to evaluate whether this has any effect on JZ contractions.
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Materials and methods |
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Procedure
Our investigations were performed before mock embryo transfer, which we do routinely in all patients at the time of down-regulation (mid-luteal phase). The patients were assessed by transvaginal ultrasound scan (ATL, Ultramark 4; 5 MHz endovaginal transducer, Advanced Technology Laboratories, Seattle, WA, USA) for 2 min to obtain baseline JZ activity. At each examination a scan image of the mid-sagittal plane of the uterus was videotaped. This was followed by application of Littlewood's tissue forceps to the upper lip of the cervix. After one movement mimicking correction of the uterine position, the instrument was released. Recording was continued for a further 2 min. The images were later digitized into a computer and converted to five times normal speed to allow analysis of JZ contractions as we have previously described in detail (Lesny et al., 1998a,b
).
We used the wave classification system introduced by Ijland et al. (1996), which includes five types of endometrial movements: no activity; waves from cervix to fundus; waves from fundus to cervix; opposing waves starting simultaneously at cervix and fundus; and random waves originating at various foci (Ijland et al., 1996). Contraction pattern and frequency were rated by two independent observers. These observations were evaluated on SPSS for Windows (SPSS UK Ltd, St Andrew's House, Woking, Surrey, UK) using Wilcoxon matched-pairs signed-ranks test.
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Results |
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Discussion |
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The ability of fundocervical contractions to move the mock embryo towards the cervix has previously been demonstrated (Lesny et al., 1998a) after stimulation of the uterine fundus with the embryo transfer catheter. Real embryos have also been found in the vagina following embryo transfer (Poindexter et al., 1986
; Schulman, 1986
). Experimental studies of mock embryo transfer in humans showed expulsion of methylene blue in 57% of transfers (Mansour et al., 1994
) and movement of X-ray contrast medium towards the cervix and vagina in 21% (Knutzen et al., 1992
). Interestingly, some of the original research on animals in the early 1960s (Harper et al., 1961
; Rowson et al., 1964
) also showed that transcervical embryo transfer was associated with expulsion of resin spheres impregnated with radioactive gold (artificial ova), whilst surgical transfer (bypassing the cervix) offered better and more consistent results (Betteridge and Rieger, 1993
). Our observation suggests that the application of Littlewood's tissue forceps may potentiate an adverse uterine response already associated with the mechanism of transcervical embryo transfer.
Theoretically, the JZ contractions in the cervicofundal direction which we saw in 11 patients (in eight cases stimulated de novo and in three patients with higher frequency than before stimulation) should have a positive effect and keep the embryos inside the uterine cavity. On the contrary, as opposing and random contractions represent the dominant pattern during the luteal phase in both natural (Ijland et al., 1996) and assisted reproduction cycles (Lesny et al., 1998b
), cervicofundal contractions may push the embryo into the Fallopian tube or prevent an embryo's descent if it is already there.
We consider the significantly increased number of the opposing waves and strong random waves after application of the tenaculum to be equally dangerous as waves of regular pattern. We have previously reported that strong random waves within the uterine fundus generated by stimulation with the transfer catheter in this area (Lesny et al., 1998a) were able to push a mock embryo through the uterotubal junction. We observed, however, that while movements of mock embryos usually occur within 5 min following transfer, the increased uterine contractility was present even 45 min later. These observations provide an explanation for earlier clinical studies (Yovich et al., 1985
; Nazari et al., 1993
). They demonstrated that their embryo transfer technique in which embryos were not placed near the uterine fundus was associated with a lower ectopic pregnancy rate without compromising the intrauterine pregnancy rate. Interestingly, during our study, we observed that the uterus responded with contractions of opposing or strong random patterns in the fundal area when we stimulated not the uterine fundus but the uterine cervix.
It is known that JZ contractions change during both natural (Ijland et al., 1996, 1997a
,Ijland et al., b
; Kunz and Leyendecker, 1996
) and stimulated cycles (Abramowicz and Archer, 1990
; Fukuda and Fukuda, 1994
; Lesny et al., 1998b
). It has been observed (Fanchin et al., 1998b
, 1999
) that at the time of embryo transfer, higher concentrations of serum progesterone were associated with contractions of lower frequency, and increased endometrial echogenicity. Indirect support for the role of progesterone as a possible regulator of JZ contractility has been provided (Mahmood et al., 1998
). They reported changes in epithelial ciliary beat frequency of the Fallopian tube, which was significantly suppressed in vitro by progesterone. This may be in agreement with the new concept of an endometrialsubendometrial unit or `archimetra', which according to one proposed theory (Leyendecker et al., 1998
; Noe et al., 1999
) is of paramesonephric origin; thus, the contractility of Fallopian tubes and JZ contractions may have similar, hormonally dependent, regulation.
Several substances were found to alter contractility of isolated myometrial strips in vitro (Morizaki et al., 1989; Martinez-Mir et al., 1990
, 1992
; Rudolph et al., 1993
) but efforts to improve uterine receptivity by trying to relax the uterus with prostaglandin synthetase inhibitors (Poindexter et al., 1986
; Schulman, 1986
), ritodrine (de Kretzer et al., 1983
), diazepam (Meldrum et al., 1987
) and glyceryl trinitrate (Shaker et al., 1993
) or by transferring embryos under general anaesthesia (Diedrich et al., 1989
), have all failed. It has recently been reported (Mori et al., 1997
) that the human uterus is characterized by a large number of mast cells. These mast cells are especially numerous in the inner part of the myometrium and are closely associated with bundles of smooth muscle cells (Mori et al., 1997
). We can only postulate that stimulation of JZ contractions during embryo transfer is caused by mast cells releasing the inflammatory reaction mediators such as histamine, serotonin and prostaglandins after application of a tenaculum to the cervix or stimulation of the endometrium and inner myometrium by an embryo transfer catheter. Thus, this local reaction and the proximity of the responding cells (densely packed myocytes of the JZ layer) may make attempts at pharmacological treatment difficult.
In summary, manipulation with a tenaculum in the cervical area stimulates JZ contractions and is best avoided at the time of embryo transfer. As the precise endocrine mechanism for these contractions is yet to be determined, pharmacological control to reduce this contractility remains elusive.
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Acknowledgments |
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Notes |
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References |
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Submitted on March 8, 1999; accepted on May 20, 1999.