Fertility and Endocrinology Centre, In-Vitro Fertilization Unit, Lister Hospital, London SW1W 8RH, UK
![]() |
Abstract |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Key words: clinical/embryo transfer/IVF/prospective study/ultrasound-guided
![]() |
Introduction |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
The technique of embryo transfer at our centre and in the majority of the centres world-wide relies on the clinical touch in positioning the transfer catheter in the upper part of the uterine cavity. It would appear that any assistance such as ultrasound guidance in ensuring that the embryos are indeed placed in this position would be desirable. Using clinical touch first and then checking with a transvaginal ultrasound, Woolcott and Stanger (1997) found 17.4% (21/121) of guiding cannulae inadvertently abutting the fundal endometrium and 7.4% (9/121) abutting the internal tubal ostia. Most studies trying to address the issue of whether ultrasound guidance is beneficial to embryo transfer conclude that although the pregnancy rate may not be significantly raised, ultrasound guidance provides both the clinicians and the patients with a greater degree of confidence in the embryo transfer procedure (Strickler et al., 1985; Leong et al., 1986
; Hurley et al., 1991
). The objective of this prospective control study is to assess the use of transabdominal ultrasound scan guidance during embryo transfer to examine if it would improve the pregnancy and implantation rate compared to the present practice of clinical touch embryo transfer. In addition, we divided our study population according to the (i) number of embryo transferred, (ii) age of patients and (iii) ease of embryo transfer to delineate a subgroup of patients that would particularly benefit from their embryos being transferred under ultrasound guidance.
![]() |
Materials and methods |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
On each of the embryo transfer days during the study period, a continuous 1 h time period was allocated for the use of the ultrasound for embryo transfers. Eligible women who had their embryo transfers during this time slot had their embryo transfers performed under ultrasound guidance (`ultrasound' group). The control group was made up of eligible women who had their embryo transfers in the usual clinical manner without the aid of ultrasound in the following hour (`clinical' group). If the `ultrasound' group was in the last hour of embryo transfer on any one day, then the `clinical' group was taken as all the patients in the preceding hour. The 1-h time period for the `ultrasound' group was not the same each day and was determined by the availability of the ultrasonographer. Neither the patients nor the person allocating the embryo transfer times knew when the ultrasonographer was doing the scanning on the day of embryo transfer.
Using this allocation process, a total of 195 women was enrolled in the study: 98 in the `ultrasound' group and 97 in the clinical group. No significant difference was observed between the two groups when comparing their age, whether they were primary or secondary infertile, duration and cause of infertility and the mean number of previous assisted conception attempts. The mean numbers of embryos available for transfer and embryos actually transferred were similar in both groups (Table I). All eligible women were told to come in on the day with a relatively full bladder but were not told whether or not they would have their embryo transfers done under ultrasound guidance. It should be noted that it is the usual clinical practice of the unit not to use ultrasound for routine embryo transfers.
|
The ovulation induction regime used was down-regulation with a gonadotrophin releasing hormone analogue followed by follicle stimulating hormone in either a short (15% of both groups) or long protocol (85% of both groups). Human chorionic gonadotrophin was given i.m. 3438 h prior to vaginal oocyte retrieval. A maximum of three embryos was transferred, 2 (69% of both groups) or 3 (31% of both groups) days following oocyte retrieval using a Wallace embryo transfer catheter (catalogue number 1816; Simcare Manufacturing Ltd, West Sussex, UK). In both `ultrasound' and `clinical' groups, the clinicians started the embryo transfer in the same way, i.e. cleaning the external genitalia with a moist swab before insertion of a sterile speculum into the vagina. The external cervical os was then cleaned with a moist cotton bud and mucus in the cervical canal was removed with a mucus extractor. The Wallace catheter was loaded in the following way: 1 µl air gap followed by 15 µl of Medicult Universal IVF medium (catalogue number 1031; Medicult a/s, Copenhagen, Denmark) containing the embryo(s) and finally another 1 µl air gap was aspirated at the end. The catheter was then handed to the clinician who inserted it through the cervical canal. At this stage there was a difference between the two groups. In the `clinical' group, when the clinician was satisfied that he/she had placed the catheter as close to the fundus as possible without touching it, the plunger was depressed; but in the `ultrasound' group, the ultrasonographers used a transabdominal ultrasound to guide the clinician in the positioning of the tip of the catheter to within 1 cm of the fundus of the uterine cavity. The plunger was then depressed and the air bubble observed to be expelled from the catheter tip. The clinician was then required to rate the embryo transfer procedure in terms of ease of transfer before they left the embryo transfer room. The rating system guideline was: very easy: transfer catheter went straight through the cervix; easy: required either the separation of the transfer catheter to advance the sheath or a stiffer catheter to facilitate the transfer; difficult: required a tenaculum in addition to those requirements in the `easy' category.
A positive pregnancy outcome was a positive blood pregnancy test performed 2 weeks after the embryo transfer and an ultrasound scan showing at least one sac in the uterine cavity 2 weeks after the positive pregnancy test. The implantation rate was defined as the number of sacs seen on ultrasound in relation to the number of embryos replaced. Subanalysis included the pregnancy rate controlled for the number of embryos transferred, the women's age and ease of transfer.
For categorical data like pregnancy outcome and implantation, Pearson's 2 test was used to test for statistical difference between the two groups. Fisher's Exact test was used if the numbers in any one cell were less than five. For continuous data, Student's t-test was used. A P value < 0.05 was considered statistically significant.
![]() |
Results |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
|
![]() |
Discussion |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
To our knowledge, this is the largest prospective study comparing clinical and ultrasound-guided embryo transfer. Like previous studies, we failed to find a significant difference in the pregnancy rate with the use of ultrasound guidance. However, there was an apparently substantial improvement in the pregnancy rate in the subgroups of older women and where the embryo transfer procedure was rated as `difficult' by the clinician which just failed to reach statistical significance. We believe that this apparent improvement can be ascribed to the accurate positioning of the embryo transfer catheter tip near the fundus of the uterus which can be confidently achieved with the use of ultrasound scan guidance. It negates factors such as inadvertent abutting of the catheter tip against the fundal endometrium or tubal ostia (Woolcott and Stanger, 1997). In our experience, on occasions, it has been observed that the catheter can curl and that the tip would actually be directed towards the cervix without any awareness of this malposition by the clinician. It is interesting to note that ultrasound was particularly helpful in women >36 years of age. It appears that precise placement of embryos is more important in this group than in younger women where perhaps better embryo quality or uterine receptivity may be able to make up for less than accurate placement.
The procedure was readily accepted by the patients who were reassured by the visualisation of the transfer process. The acceptance by the clinicians was also high with no significant added time, and the procedure was done with more confidence as the catheter is advanced to the fundus of the uterus under ultrasound scan guidance. It has thus been proposed, in the light of this study, that difficult embryo transfers, especially in older women, be conducted under ultrasound guidance.
![]() |
Notes |
---|
![]() |
References |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Edwards, R.G., Steptoe, P.C. and Purdy, J.M. (1980) Establishing full-term human pregnancies using cleaving embryos grown in vitro. Br. J. Obstet. Gynaecol., 87, 737756.[ISI][Medline]
Fanchin, R., Righini, F.O., Taylor, S. et al. (1998) Uterine contractions at the time of embryo transfer alter pregnancy rates after in-vitro fertilization. Hum. Reprod., 13, 19681974.[Abstract]
Hurley, V.A., Osborn, J.C., Leoni, M.A. et al. (1991) Ultrasound-guided embryo transfer: a controlled trial [see comments]. Fertil. Steril., 55, 559562.[ISI][Medline]
Leong, M., Leung, C., Tucker, M. et al. (1986) Ultrasound-assisted embryo transfer. J. In Vitro Fert. Embryo Transf., 3, 383385.
Prapas, Y., Prapas, N., Hatziparasidou, A. et al. (1995) The echoguide embryo transfer maximizes the IVF results. Acta Eur. Fertil., 26, 113115.[Medline]
Speirs, A.L. (1988) The changing face of infertility. Am. J. Obstet. Gynecol., 158, 13901394.[ISI][Medline]
Strickler, R.C., Christianson, C., Crane, J.P. et al. (1985) Ultrasound guidance for human embryo transfer. Fertil. Steril., 43, 5461.[ISI][Medline]
Woolcott, R. and Stanger, J. (1997) Potentially important variables identified by transvaginal ultrasound-guided embryo transfer. Hum. Reprod., 12, 963966.[ISI][Medline]
Submitted on August 27, 1998; accepted on December 16, 1998.