The success of
Most ET are easy and do not require the use of
force or manipulation. Different attempts have
been suggested to prevent technically difficult ET,
such as the performance of a dummy ET in order
to ascertain the depth and direction of the uterus,
Because a difficult ET has been shown to cause
a significant reduction in pregnancy rate (
This prospective study was performed at Royan Institute for Reproductive Biomedicine over a 12- month period between May 2009 and May 2010. All eligible cases were included at study duration. We analyzed the results of 706 ET procedures. There were six specialists who performed all the ET procedures, each of them had more than four years of experience.
Inclusion criteria for participation in the study were: maternal age≤41 years, early follicular phase (day3) follicle stimulating hormone (FSH) ≤15 IU/L, and the presence of at least one grade A or B embryo on days 2-3 after oocyte retrieval.
Patients with a hydrosalpinx and abnormal uterine cavity, endometrial thickness <7mm at the time of hCG injection, or those who were candidates for blastocyst transfer, freeze-thaw embryo, oocyte donation, or surrogated cycles were excluded from this study.
This study was approved by the Ethics Committee of Royan Institute at the Reproductive Biomedicine Center. Written informed consent was obtained from all participants prior to study entry.
All patients received the standard long protocol
as described elsewhere (
All ET were performed using a soft ET catheter (Labotect GmbH, Göttingen, Germany) without ultrasound guidance. This catheter system has an outer sleeve and a soft open ended inner catheter. The patient was placed in the lithotomic position with an empty bladder)according to our center's protocol). A sterile bivalve speculum was placed in the vagina and the cervix exposed. Each ET was performed without anesthesia.
All patients underwent a mock ET or trial transfer performed 1-2 months before the IVF cycle with the intent to determine the uterine cavity depth and map the direction of the cervix and uterus.
After cleaning the cervix with a sterile swab soaked with saline followed by a dry swab, the outer sheet was passed gently through the external os until the tip passed the internal os. Then, an embryologist loaded the embryos into the transfer catheter after which they were deposited into the uterine cavity. The tip of the inner catheter was placed 6-6.5 cm from the external cervical os and embryos were placed 1-2 cm from the uterine fund us. After removal of the ET catheter, patients remained in the supine position for 20 minutes. We classified all ET procedures as easy or difficult. This study defined an easy ET procedure as a smooth procedure that occurred without the use of any force or other instrumentation, with no need to change the catheter. A difficult ET had at least one of the following problems: the placement of the outer sheet required force, use of a stylet, use of a tenaculum to grasp the cervix and/or manipulation with a hysterometer.
The primary endpoint was clinical pregnancy. We measured serum βhCG levels 14 days after ET and defined clinical pregnancy as the presence of a gestational sac with fetal heart activity at seven weeks of gestation. Pregnancy rate was calculated by dividing the number of clinical pregnancies detected by the number of patients (clinical pregnancies/ patient).
Statistical analysis was performed using the Statistical Packages for Social Sciences (version 13.0; SPSS Inc., Chicago, IL, USA). The normality in the distribution of continuous variables was assessed using the Kolmogorov-Smirnov test. Inter-group differences of normally distributed continuous variables were assessed by parametric statistics (student’s t test), whereas non-parametric statistics (Mann-Whitney U test) were used if the data were not normally distributed. Significant differences were evaluated by the chi-square test to compare non-continuous variables. Data were expressed as mean ± standard deviation (SD) unless otherwise specified. Statistical significance was set at p<0.05.
From May 2009 to May 2010, we included 706
patients in this study. Of these, there were 81.4%
(575) easy ET and 18.6% (131) graded as difficult.
There were no significant differences between the
two groups as to the baseline or cycle characteristics
Table 2 shows the distribution of the ET classification. Difficult ET was divided as follows: ET necessitating the use of force; astylet was used, and ET that used a tenaculum, or the combination of these methods.
Implantation was significantly higher in the easy group (21.7%) compared to the difficult group (12.1%; p<0.05; OR=2.014; 95% CI:1.404-2.890).
Additionally, the easy group also had a higher pregnancy rate (38.1%) compared with patients who had difficult ET (21.4%; p<0.05;OR= 2.263; 95% CI: 1.442-3.550).
In the easy ET group, 9(1.6%) out of 575 patients
had early abortions, compared with one
early abortion (0.8%) in the difficult ET group
(p>0.05). Four patients in the easy ET group had
ectopic pregnancies, but there were no ectopic
pregnancies in patients who underwent difficult
Comparison of baseline demographic and clinical characteristics of the two study groups during ICSI/ET cycles
|Group A (easy ET) (n= 575)||Group B (difficult ET) (n= 131)||P value|
|31.05 ± 4.84||30.8 ± 5.28||0.590|
|26.2 ± 4.89||26.3 ± 4.18||0.783|
|8.4 ± 4.94||8.4 ± 5.11||0.884|
|357 (62.1%)||82 (62.6%)||0.724|
|99 (17.2%)||22 (16.8%)|
|84 (14.6%)||16 (12.2%)|
|35 (6.1%)||11 (8.4%)|
|547 (95.1%)||129 (98.5%)||0.087|
|28 (4.9%)||2 (1.5%)|
|10.2 ± 1.86||10.4 ± 2.27||0.224|
|6.6 ± 3.19||6.7 ± 3.26||0.860|
|5.2 ± 3.81||5.2 ± 3.64||0.952|
|10.1 ± 4.70||9.4 ± 4.45||0.131|
|4.9 ± 2.98||4.6 ± 2.99||0.248|
|2.12 ± 2.05||1.8± 2.03||0.103|
|9.9 ± 1.76||9.7 ± 1.71||0.252|
Values are as mean ± SD.
Distribution of ET types
|Types of ET||Number||Percent|
Cycle outcomes of 706 patients following difficult or easy ET
|Easy ET (n= 575)||Difficult ET (n= 131)||P value||Odds ratio (95% CI)|
|219 (38.1)||28 (21.4)||<0.001||2.263 (1.442-3.550)|
|320/1474 (21.7)||38/314 (12.1)||<0.001||2.014 (1.404-2.890)|
|9 (1.6)||1 (0.8)||0.483||2.067 (0.260-16.460)|
|4 (0.7)||0 (0)||0.338||1.229 (1.187-1.274)|
*;Statistically significant .
Values in parentheses are percentages.
In this study, those who experienced difficult ET
showed lower implantation and pregnancy rates.
The impact of a difficult ET on the success of IVF
cycles has remained a subject of debate in studies.
Some studies have shown a negative correlation
between difficult ET and pregnancy rate (
In the current study all patients underwent a
mock ET or trial transfer performed 1-2 months
before the IVF cycle; at that time the uterine cavity
depth and direction of the cervix and uterus
were mapped. Different treatments such as cervical
dilatation by a Hegar dilator, (
ET should be smooth with easy passage of the transfer catheter. Since any uterine manipulation during ET adversely affects IVF results, therefore precaution should be taken to identify possibly difficult ET cases in advance. Additional studies regarding the numerous details of the ET technique appear to be essential.