Ultrasound-guided embryo transfer: immediate withdrawal of the catheter versus a 30 second wait

F. Martínez1,, B. Coroleu, M. Parriego, O. Carreras, I. Belil, N. Parera, L. Hereter, R. Buxaderas and P.N. Barri

Servicio de Medicina de la Reproducción, Instituto Universitario Dexeus, Pso Bonanova 67, 08017 Barcelona, Spain


    Abstract
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 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
It is essential to deposit embryos as gently as possible during IVF, avoiding manoeuvres that might trigger uterine contractions which could adversely affect the results of this treatment. The time during which the embryo transfer catheter remains in the cervical canal might be related to stimulation of contractions. This study investigates the influence that the time interval before withdrawal of the catheter after ultrasound (US)-guided embryo deposit might have on the pregnancy rate in patients under IVF cycles. A total of 100 women about to undergo transfer of at least two optimal embryos was studied. The women were prospectively randomized into two groups: (i) slow withdrawal of the catheter immediately after embryo deposit (n = 51); and (ii) a 30 s delay before catheter withdrawal (n = 49). The pregnancy rates for transfer in the two groups were 60.8 and 69.4% respectively, with no significant differences. There were no statistically significant differences in pregnancy rates between the two patient groups. The results indicate either that the waiting interval was insufficient to detect differences, or that the retention time before withdrawing the catheter is not a factor that influences pregnancy rate.

Key words: embryo transfer/IVF/ultrasound-guided/uterine contractions/waiting time


    Introduction
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Over recent years, increasing attention has been placed on the moment of embryo transfer during IVF. It is important that the embryo be deposited in the uterine cavity in the least traumatic manner possible (Mansour et al., 1990Go), without touching the uterine fundus and without manipulation within the cervical area (Lesny et al., 1998Go, 1999aGo). Ultrasound (US)-guided embryo transfer has proved to be useful in women with a previous difficult transfer (Kan et al., 1999Go), and its systematic use significantly improves implant and pregnancy rates (Coroleu et al., 2000Go). Brusque manoeuvres during a difficult embryo transfer may reduce the possibility of pregnancy (Lesny et al., 1998Go), probably by stimulating uterine contractions that would expel the embryo (Fanchin et al., 1998Go). It has been observed that, after embryo transfer, the embryo can move as easily toward the cervical canal as toward the Fallopian tube (Woolcott and Stanger, 1997Go), increasing the risk of ectopic pregnancy (Lesny et al., 1999bGo).

In addition to traumatic manipulation of the cervix and touching the fundus, the mere presence of the transfer catheter might be one of the factors that can trigger uterine contractions (Lesny et al., 1999aGo). Some authors have suggested that it is preferable to wait before retiring the catheter so that the uterus can become stabilized (Wisanto et al., 1989Go), whereas others report good results withdrawing the catheter immediately after an easy transfer (Zech et al., 1997Go).

In the IVF programme of the Reproductive Medicine Department of the Institut Universitari Dexeus it was decided to evaluate the hypothesis that to include a delay before catheter withdrawal during embryo transfer has an influence on pregnancy rate. A prospective comparative study was designed to determine whether there were differences in pregnancy rates in IVF cycles with easy embryo transfer between immediate catheter withdrawal and a 30 s delay before withdrawal. The study was approved by the centre's Committee for Ethics and Clinical Trials. The patients' informed written consent was not considered necessary, as no procedure was performed other than that required for the treatment solicited.


    Materials and methods
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Patient selection
A total of 100 IVF patients who had received at least two embryos of good quality (Plachot et al., 1990Go) between June and October 1999, and who presented no difficulties during transfer, were prospectively included in the study. All the participants had been stimulated with gonadotrophins (Neofertinorm; Serono, Madrid, Spain) under pituitary suppression with analogues (Procrin; Abbot, Madrid, Spain), according to a previously described long protocol (Coroleu et al., 2000Go). Embryo transfer was performed 2–3 days after follicle puncture (n = 64), or blastocyst transfer 5–6 days after follicle puncture (n = 36). Support treatment during the luteal phase consisted of intravaginal administration of 200 mg micronized progesterone (Utrogestan; Seid, Barcelona, Spain) three times daily, beginning the second day after follicle puncture and continuing until negative pregnancy outcome was confirmed by plasma ß human chorionic gonadotrophin (ßHCG) concentrations in serum were <5 IU, or until the 6–8th week of amenorrhoea in the case of pregnancy.

The details of the IVF laboratory procedures used, including intracytoplasmic sperm injection (ICSI) have been described previously (Calderón et al., 1995Go; Boada et al., 1997Go). Two or three embryos were selected for transfer according to their state of division and morphology (Plachot et al., 1990Go; Veiga et al., 1999Go). In order to reduce the risk of multiple pregnancy, the number of embryos transferred was determined taking into consideration the age of the patient, the number of available embryos and the number of previous IVF cycles (Tur, 1994Go). After confirming that the patient fulfilled the inclusion criteria (stimulation treatment according to the protocol and availability of at least two optimal embryos) the patients were randomized prospectively into two groups: (i) slow withdrawal of the catheter immediately after embryo injection; or (ii) withdrawal of the catheter after a 30 s wait, as determined by chronometer. The randomization table was computer-generated.

Embryo transfer technique
The two groups were submitted to the same (previously described) US-guided embryo transfer technique (Coroleu et al., 2000Go). Briefly, after visualization of the cervix, the cervical mucus was removed with a cotton swab soaked in phosphate-buffered saline solution (PBS) (Dulbecco's PBS solution; Irvine Scientific, Santa Ana, CA, USA). The cervix was irrigated with the same solution and the cervical canal content was aspirated with a sterile Teflon catheter (Malleable Stylet Wallace, SIMCARES, Lancing, West Sussex, UK) connected to a syringe.

For embryo transfer, a Wallace-Edwards catheter (SIMS Portex Ltd, Kent, UK) connected to an insulin syringe was used. Avoiding the formation of air bubbles, the catheter was loaded with transfer medium [50% synthetic serum substitute (Irvine Scientific) and IVF medium (IVF-50) or G2.2 medium (Scandinavian IVF Science, Gothenburg, Sweden)], according to the state of evolution of the embryos or blastocysts. The embryos were then loaded and the catheter was handed to the clinician who inserted it through the endocervical canal. The insertion of the catheter and the position in which the embryos were deposited (1 cm from the fundus of the uterine cavity) was visualized in all cases. Contact with the fundus was avoided. Transabdominal ultrasound was performed with the bladder partly filled [Toshiba, Barcelona, Spain; TOSBEE (SSA-240) convex 3.75 MHz]. The embryos were gently injected into the uterine cavity in a volume of 20–30 µl of transfer medium. At this point, according to the randomization table, the catheter was either slowly withdrawn or withdrawn after a 30 s delay, as measured by chronometer. The biologist confirmed that no embryo remained in the catheter by means of stereo microscopy. The transfer was rated as: `very easy' when the catheter passed smoothly through the cervical canal; `easy' when the catheter required a stiff external sheath to pass through the internal cervical os (ICO) (but the rigid part did not pass beyond this point); and `difficult' when it was necessary to apply a tenaculum or the use of other manoeuvres. No case of difficult transfer was included in this study.

A positive pregnancy was established by ßHCG determination in blood 14 days after recovery of the oocytes, and confirmed by ultrasound at 6–8 weeks of amenorrhoea. Only clinical pregnancies with sonographic confirmation of the embryonic sac were included in the study.

Data analysis
Statistical analysis was performed with the SPSS 9.0 software program for Windows (Chicago, IL, USA). The {chi}2-test was used to compare qualitative variables, and Student's t-test to compare quantitative variables. Significance was set at a P-value < 0.05.


    Results
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
One hundred consecutive patients who had completed an IVF cycle and transfer of at least two optimal embryos were studied, and 65 clinically confirmed pregnancies were obtained (65% pregnancy rate by transfer). In 51 patients the transfer catheter was withdrawn immediately after depositing the embryos in the uterus (immediate withdrawal group), and in 49 patients the clinician waited 30 s before withdrawing the catheter (30 s wait group). The mean age of the patients included in the present study was 34.42 ± 4.10 years. There were no differences between the groups with regard to age, body mass index (BMI; weight in kg/height in m2), and cause of infertility (Table IGo). The response to stimulation presented by the patients was considered favourable, taking into account the total number of ampoules of gonadotrophins administered (mean 32.06 ± 10.98), mean plasma oestradiol concentrations on the day of HCG administration (2050 ± 882 pg/ml) and mean number of oocytes retrieved (15.56 ± 7.5). There were no statistically significant differences in response during the IVF cycle, total number of ampoules of gonadotrophins used, days of stimulation, concentrations of oestradiol on the day of HCG administration or number of oocytes recovered, between the two groups studied. The overall fertilization rate was 75.32%. There were no significant differences between the two groups. A similar number of growing embryos was obtained in both groups (Table IIGo). Thirty-two embryo transfers were performed 2–3 days after follicle puncture in both groups. Nineteen blastocyst transfers were performed 5–6 days after follicle puncture in the immediate-withdrawal group, and 17 blastocyst transfers in the 30 s wait group. There were no differences in the day of the transfer between the two groups (Table IIGo).


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Table I. Characteristics of the IVF patients
 

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Table II. Characteristics of the response during the IVF cycle in the two groups
 
In all cases embryo transfer was `easy', as was required for inclusion in the study. A mean of 2.87 ± 0.54 embryos were transferred per patient, at least two of which were of good quality (there were no statistical differences between the two groups in the number of embryos transferred).

Thirty-one pregnancies were obtained in the immediate-withdrawal group and 34 in the 30 s wait group, giving pregnancy rates by transfer of 60.8 and 69.4% respectively. There were no statistically significant differences in the pregnancy rates between the groups.


    Discussion
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
The present study was conducted to investigate whether the time in which the catheter remains within the ICO after embryo transfer influences the pregnancy rate in IVF cycles. In order to minimize the effect of other factors related with the moment of transfer, the study included only transfers of at least two embryos of good quality performed under strict criteria of uniformity of technique and in which there were no difficulties. The two groups were similar in age, infertility factor, type of stimulation treatment and stimulation response, as well as in number and quality of embryos transferred.

The importance of depositing the embryos as gently as possible in the uterine cavity has been demonstrated in several studies (Mansour et al., 1990Go; Kan et al., 1999Go; Lesny et al., 1999aGo). It has been observed that some manoeuvres, such as the use of tissue forceps to grasp the cervix or touching the fundus, can trigger uterine contractions (Lesny et al., 1999aGo), which might negatively influence the pregnancy rate in IVF cycles (Fanchin et al., 1998Go). The stimulus of the transfer catheter passing through the ICO can also initiate contractions, probably mediated by the release of prostaglandins (Fraser, 1992Go).

The time during which the transfer catheter is retained in the uterine canal might constitute an additional stimulus, and delayed withdrawal of the catheter might result in uterine stabilization, fewer contractions and a better pregnancy rate than immediate withdrawal. However, contradictory reports have been made regarding this waiting time. One group (Zech et al., 1997Go) reported excellent results when withdrawing the catheter immediately, whereas others (Wisanto et al., 1989Go) recommended leaving the catheter in situ for up to 60 s. If the mechanism stimulating uterine contractions is mediated by prostaglandin release, it would be triggered by the passage of the catheter through the ICO, and the retention time would not reduce the contractions produced. The present study did not directly evaluate uterine contractions, and only `easy' embryo transfers were included to eliminate other potential mechanical or physical stimuli that could trigger contractions.

No differences were found in pregnancy rates between patients in whom the catheter was withdrawn immediately after depositing the embryos and those in whom it was withdrawn after a 30 s wait. These results indicate that either the retention time was not long enough to detect differences, or that delayed withdrawal of the catheter does not influence the appearance of uterine contractions. The latter conclusion supports the findings of others (Lesny et al., 1998Go), who demonstrated uterine contractions up to 45 min after a difficult transfer and suggested that it was not useful to wait for the uterus to stabilize.

Other measures have been proposed to reduce the potentially detrimental effect of uterine contractions, such as the use of various substances to relax the uterus (e.g. progesterone, ß-mimetics, anti-prostaglandins, nitric oxide donors), though to date only progesterone has shown any uterus-relaxing effect (Fanchin et al., 1998Go). In the present study, plasma progesterone concentrations were not determined; and in any case they would not reflect the action of the hormone at the level of the uterus. All the patients had presented an adequate response to stimulation, as evidenced by plasma oestradiol concentrations on the day of HCG administration, and all received the same intravaginal dose of micronized progesterone as support treatment for the luteal phase.

The small difference in pregnancy rate observed in this series might have reached statistical significance if a population of 1000 cases had been included. However, in order to gather such a large number of patients conforming to the strict patient selection criteria, intended to guarantee maximum homogeneity between the groups, the duration of the study would necessarily be greatly prolonged, making it difficult to maintain uniformity in all the other steps (stimulation, laboratory, etc.) and derive valid conclusions.

In summary, no differences were observed in the pregnancy rate between withdrawal of the catheter immediately after embryo deposit or after a 30 s wait in a population of women with good response to stimulation and `easy' US-guided transfer of at least two optimal embryos. These results indicate that either this waiting interval is not sufficient to detect differences, or that retention of the transfer catheter after depositing the embryos is not a factor that affects the pregnancy rate.


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Table III. Number of embryos transferred and pregnancy rate
 

    Notes
 
1 To whom correspondence should be addressed: E-mail: pacmar{at}iudexeus.uab.es Back


    References
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Boada, M., Coroleu, B., Calderon, G. et al. (1997) Resultados del Programa de Fecundación In vitro del Instituto Universitario Dexeus, 1996. Prog. Obstet. Ginecol., 40, 691–699.

Calderon, G., Belil, I., Arán, B. et al. (1995) Intracytoplasmic sperm injection versus conventional in-vitro fertilization: first results. Hum. Reprod., 10, 2835–2839.[ISI][Medline]

Coroleu, B., Carreras, O., Veiga, A. et al. (2000) Embryo transfer under ultrasound guidance improves pregnancy rates after in-vitro fertilization. Hum. Reprod., 15, 616–620.[Abstract/Free Full Text]

Fanchin, R., Righini, C., Olivennes, F. et al. (1998) Uterine contractions at the time of embryo transfer alter pregnancy rates after in-vitro fertilization. Hum. Reprod., 13, 1968–1974.[Abstract]

Fraser, I.S. (1992) Prostaglandins, prostaglandin inhibitors and their roles in gynaecological disorders. Baillieres Clin. Obstet. Gynaecol., 6, 829–857.[ISI][Medline]

Kan, A.K.S., Abdalla, H.I. and Gafar, A.H. (1999) Embryo transfer: ultrasound-guided versus clinical touch. Hum. Reprod., 14, 1259–1261.[Abstract/Free Full Text]

Lesny, P.L., Killick, S.R., Tetlow, R.L. et al. (1998) Embryo transfer-can we learn anything new from the observation of junctional zone contractions. Hum. Reprod., 13, 1540–1546.[Abstract]

Lesny, P.L., Killick, S.R., Robinson, J. et al. (1999a) Junctional zone contractions and embryo transfer: is it safe to use a tenaculum?. Hum. Reprod., 14, 2367–2370.[Abstract/Free Full Text]

Lesny, P.L., Killick, S.R., Tetlow, R.L. et al. (1999b) Transcervical embryo transfer as a risk factor for ectopic pregnancy. Fertil. Steril., 72, 305–309.[ISI][Medline]

Mansour, R., Aboulghar, M. and Serour, G. (1990) Dummy embryo transfer: a technique that minimizes the problems of embryo transfer and improves the pregnancy rate in human in vitro fertilization. Fertil. Steril., 54, 678–681.[ISI][Medline]

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Tur, R. (1994) Embarazo múltiple en reproducción asistida: análisis de posibles factores de riesgo. Doctoral Thesis, Universidad de Barcelona, Barcelona.

Veiga, A., Torello, M.J., Ménézo, Y. et al. (1999) Use of colculture of human embryos on Vero cells to improve clinical implantation rate. Hum. Reprod., 14 (Suppl.), 112–120.[Medline]

Wisanto, A., Janssens, R., Deschacht, J. et al. (1989) Performance of different embryo transfer catheter in a human in vitro fertilization program. Fertil. Steril., 52, 79–84.[ISI][Medline]

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Zech, H., Stecher, A., Riedler, I. et al. (1997) High implantation rate with a fast and atraumatic embryo transfer technique. Hum. Reprod., 12 (Abstract Bk 1), p. 156[Abstract]

Submitted on October 31, 2000; accepted on February 12, 2001.