1 Department of Obstetrics and Gynaecology, the University of Alexandria, and 2 Alexandria Fertility Center, Alexandria, Egypt
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Abstract |
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Key words: embryo transfer/IVF/pregnancy rate/ultrasound/uterocervical angle
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Introduction |
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Numerous attempts to improve the technique of embryo transfer have been described, including the need for a gentle and atraumatic technique (Nabi et al., 1997; Goudas et al., 1998
), performing a trial transfer before the actual procedure (Mansour et al., 1990
; Sharif et al., 1995
), removing the cervical mucus prior to embryo transfer (Mansour et al., 1994
; Nabi et al., 1997
), avoiding the use of a tenaculum (Lesny et al., 1999a
), using specific catheters (Ghazzawi et al., 1999
; Wood et al., 2000
), depositing the embryos near the uterine fundus (Egbase et al., 2000
), using a fibrin sealant (Feichtinger et al., 1992
; Ben-Rafael et al., 1995
), routine administration of antibiotics following embryo transfer (Fanchin et al., 1998a
; Egbase et al., 1999
), as well as performing the procedure under ultrasound guidance (Strickler et al., 1985
; Hurley et al, 1991
; Prapas et al., 1995
, 2001
; Woolcott and Stanger, 1997
; Kan et al., 1999
; Lindheim et al., 1999
; Coroleu et al., 2000
; Wood et al., 2000
; Tang et al., 2001
).
Abdominal ultrasound was used mainly in ultrasound-guided transfers (Strickler et al., 1985; Prapas et al., 1995
, 2001
; Kan et al., 1999
; Lindheim et al., 1999
; Coroleu et al., 2000
; Wood et al., 2000
; Tang et al., 2001
), but transvaginal ultrasound-guided embryo transfer has also been described (Hurley et al., 1991
; Woolcott and Stanger, 1997
). However, in all these studies, although ultrasound was used to confirm that the embryos have been properly deposited inside the uterine cavity and to follow the embryo-associated air bubble afterwards, no attempt was made to measure the uterocervical angle and mould the catheter accordingly.
The aim of this study was to measure the uterocervical angle immediately before embryo transfer by use of abdominal ultrasound, and to mould the transfer catheter according to the degree of angulation. It was hypothesized that this modified technique would result in improved clinical pregnancy and implantation rates in patients undergoing IVF and ICSI.
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Materials and methods |
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Measurement of the uterocervical angle
Measurement of the uterocervical angle was performed using abdominal ultrasound (Scanner 100 LC; Pie Medical, Maastricht, the Netherlands) immediately before embryo transfer, and with the patient in the lithotomy position. Patients were asked to maintain a full urinary bladder before the procedure was carried out. A transabdominal ultrasound scan was then performed and a mid-plane longitudinal section obtained. The uterocervical angle is the angle between a line joining the external cervical os and internal cervical os, and a line joining the internal cervical os and uterine fundus. Patients were divided into four categories depending on the degree of angulation: (i) no angle, Figure 1A; (ii) small angle (<30°, Figure 1B
); (iii) moderate angle (3060°, Figure 1C
); and (iv) large angle (>60°, Figure 1D
).
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A Frydman TDT catheter (CCD) was used in all cycles. This catheter consists of an outer rigid sheath with an obturator and an inner soft catheter. The outer sheath with its obturator was passed first through the cervix until located 1 cm above the internal cervical os. In ultrasound-guided transfer patients, this outer sheath (with its obturator) was moulded while still in its sterile sleeve, according to the uterocervical angle measured. In control patients, no ultrasound was used and the outer sheath was passed through the cervix using the clinical feel method. All transfers were performed by the same clinician (H.N.S.).
Once the outer sheath was in place, the embryologist (A.F.R.) was informed. The inner soft catheter was then fitted with a 1 ml tuberculin-type syringe and flushed with culture medium (BM9). The embryos were then loaded in the distal end of the inner catheter in a volume of 1525 µl of culture medium (BM9) preceded and followed by 1 cm of air. The inner catheter containing the embryos was then advanced inside the outer catheter to 1 cm below the uterine fundus, according to the uterine length obtained by sounding at the initial visit of the patient. The embryos were then gently deposited into the uterine cavity. The catheter was left in situ for 3060 s and then withdrawn gently. In the ultrasound-guided group the position of the catheter tip and the release of the air bubble containing the embryos in the uterine fundus were also confirmed by ultrasound, by a third clinician (A.F.A.) holding the abdominal transducer throughout the procedure. In all cases, the catheter was then checked under a dissecting microscope for retained embryos. If these were found, they were reloaded and transferred again. The patients were asked to remain in bed for 1530 min after the procedure.
Data analysis
Statistical analysis was performed using the Microstat software package. The 2-test was used to compare qualitative variables, and Student's t-test to compare quantitative variables. The significance level was set at P = 0.05. The analysis was carried out on an intention-to-treat basis.
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Results |
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Clinical pregnancy and implantation rates
A total of 143 clinical pregnancies (22.3%) resulted (Tables II and III). Of these pregnancies, 84 occurred in the ultrasound-directed group (26.25%) and 59 in controls (18.43%); this difference was statistically significant (
2 = 5.628, P < 0.02). The OR for increasing the clinical pregnancy rate were 1.57 (95% CI 1.082.27). A total of 1824 embryos was replaced; of these, 928 were in the ultrasound-guided group (mean 2.9 embryos per transfer) and 896 in the control group (mean 2.8 embryos per transfer). A total of 128 embryos was implanted in the ultrasound-guided group (implantation rate 13.79%) compared with 88 in controls (implantation rate 9.82%); this difference was also statistically significant (
2 = 6.888, P < 0.01). The ORs for increasing the implantation rate were 1.47 (95% CI 1.101.96). One ectopic pregnancy occurred in the ultrasound-guided group (0.3%) and three in the control group (0.9%), but this difference was not statistically significant (
2 = 1.006, P = 0.3158).
Relationship between uterocervical angle and clinical pregnancy rate
In the ultrasound-guided group, no uterocervical angle was seen in 39 (12.2%) of the 320 cycles studied, a small angle (<30°) was found in 32 cycles (10%), a moderate angle (3060°) in 119 cycles (37.2%), and a large angle (>60°) in 130 cycles (40.6%). The clinical pregnancy rates were 35.9, 34.4, 31.1 and 16.9% respectively in these four subgroups (Table IV). When compared with patients with no uterocervical angle, the clinical pregnancy rate was significantly diminished in patients with large angles (
2 = 6.443, P < 0.02), but not with patients with either small angles [
2 = 0.018, P = 0.8937 (not significant)] or moderate angles [
2 = 0.30, P = 0.5775 (not significant)]. The OR for diminished pregnancy rates for patients with large angles compared with those with no angles were 0.36 (95% CI 0.160.52).
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Relationship between presence of blood during embryo transfer and clinical pregnancy rate
Among 143 pregnancies that occurred in 640 cycles studied, 113 were in 447 cycles with no blood found during transfer (25.3%), compared with 30 in 193 cycles with blood found during transfer (15.5%). This difference was statistically significant (2 = 7.363; P < 0.01). The OR for diminished pregnancy rates in cycles with blood during embryo transfer compared with those with bloodless transfers were 0.54 (95% CI 0.350.84).
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Discussion |
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In all these studies, however, ultrasound was mainly used to confirm that the tip of the transfer catheter was correctly positioned in the uterine fundus before embryos were actually deposited, and to follow the embryo-associated air bubble afterwards. In the present study, ultrasound was mainly used to measure the uterocervical angle immediately before embryo transfer, and the outer sheath of the TDT catheter was moulded according to the angle before its introduction into the uterine cervix. Ultrasound was also used to confirm the correct deposition of embryos into the uterine fundus. The results showed that this new technique improves both clinical pregnancy and implantation rates when embryo transfer is performed 48 hours after oocyte retrieval.
It was necessary to measure the angle immediately before the transfer, as it was found during preliminary studies that the uterocervical angle changes with the state of bladder fullness. Although, as had been suggested previously (Lewin et al., 1997), patients were asked to maintain a full bladder in order to straighten the uterus, only 12.2% of them had no uterocervical angle during transfer, and 40.6% had an angle >60°. The clinical pregnancy rate was found to be significantly diminished for patients with larger angles (>60°) compared with those with no angle, and it is suggested that these patients should have a very full bladder during transfer. Whether the routine use of a volsellum in these patients would improve the pregnancy rate remains to be seen (Johnson and Bromham, 1991
), as recent studies have shown that this practice leads to the initiation of uterine contractions (Dorn et al., 1999
; Lesny et al., 1999a
).
The incidence of ectopic pregnancies was also lower in the ultrasound-guided group than in the clinical feel group, but the difference was not statistically significant; however, this may have been due to the infrequent nature of extrauterine pregnancies. Previous studies have shown that correct positioning of the catheter in relation to uterine size diminishes the incidence of ectopic pregnancies (Egbase et al., 2000), and that difficult embryo transfers were associated with an increased incidence of ectopic pregnancies (Lesny et al., 1999b
).
The present study also showed that ultrasound measurement of the uterocervical angle before embryo transfer significantly diminished the incidence of difficult transfers. In particular, the incidences of negotiating the cervical canal and using a volsellum were significantly reduced in the ultrasound-guided group compared with the clinical feel group. The use of a volsellum has been shown previously to release oxytocin (Dorn et al., 1999) and to initiate junctional zone uterine contractions (Lesny et al., 1999a
), the presence of which was also found to diminish pregnancy and implantation rates (Fanchin et al., 1998b
).
Changing the embryo transfer catheter to a more rigid one with a ball point was necessary in three cases in the ultrasound-guided group compared with five cases in the clinical feel group. Embryos were also retained inside the catheter in three ultrasound-guided patients compared with four in controls, whilst a repeat transfer was carried out in seven instances. These differences were not statistically significant, and previous studies have shown that these practices (changing the catheter and repeated transfers) do not adversely affect either IVF pregnancy rates or outcome (Nabi et al., 1997; Tur-Kaspa et al., 1998
).
It was found that difficult transfers were associated with lower clinical pregnancy rates compared with easy transfers, though the difference was not statistically significant. The results of the present study agree with those of others (Tur-Kaspa et al., 1998; Burke et al., 2000
), who found no difference in pregnancy rates between easy and difficult transfers. On the contrary, our technique was found to reduce significantly the incidence of blood appearance during transfers, thereby confirming the opinion of many IVF experts in Australia and the UK who reported that avoidance of blood during embryo transfer was the second most important prerequisite for a successful transfer (Kovacs, 1999
; Salha et al., 2001
). The present findings also agree with other reports which showed that blood outside, but not inside, the catheter after embryo transfer was associated with reduced rates of embryo implantation and clinical pregnancy (Goudas et al., 1998
). These findings therefore suggest that measuring the uterocervical angle with ultrasound before embryo transfer increases the clinical pregnancy and implantation rates mainly by diminishing bloody rather than difficult transfers. The presence of blood during embryo transfer occurred more often in the present study than in others, perhaps due to the fact that a catheter with a rigid outer sheath was used throughout. However, this incidence could most likely be reduced with the use of softer catheters, but this must be confirmed by a comparative study (Wood et al., 2000
).
In the present study, transvaginal transmyometrial embryo transfer was performed on one occasion in a control patient due to difficulty in bypassing the internal cervical os even after ultrasound use, though the patient did not become pregnant. This technique has been described previously and resulted in a clinical pregnancy rate of 36.5% per attempt (Kato et al., 1993), whilst others reported three clinical pregnancies out of 13 attempts (Sharif et al., 1996
).
Although the present study was not randomized controlled in design, it was felt that strict adherence to the policy of alternate allocation and the large number of patients studied were the next best alternatives. It has been calculated that the least number needed to treat in order to improve the pregnancy rate from 18 to 28% was 296 patients in each arm of the study, taking 5% as the significance level and accepting an 80% probability of finding a true difference. Nevertheless, a randomized controlled study is needed to confirm the present findings.
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Notes |
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References |
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Submitted on December 31, 2001; resubmitted on February 11, 2002; accepted on March 12, 2002.