An assessment of alternative policies for embryo transfer in an in vitro fertilization-embryo transfer program

Number of embryos for transfer following in-vitro fertilisation or intra-cytoplasmic sperm injection

BACKGROUND

Multiple embryo transfer during IVF has increased multiple pregnancy rates (MPR) causing maternal and perinatal morbidity. Elective single embryo transfer (SET) is now being considered as an effective means of reducing this iatrogenic complication.

OBJECTIVES

To determine in couples undergoing IVF/ICSI (intra-cytoplasmic sperm injection) whether:(1) elective transfer of two embryos improves the probability of livebirth compared with:(a) elective single embryo transfer,(b) three embryo transfer (TET) or(c) four embryo transfer (FET).(2) elective transfer of three embryos improves the probability of livebirth compared with:(a) elective single embryo transfer, or(b) elective four embryo transfer.

SEARCH STRATEGY

We searched the Cochrane Menstrual Disorders and Subfertility Group's trials register (searched March 2008), the Cochrane Central Register of Controlled Trials (Cochrane Library, Issue 1, 2008), MEDLINE (1970 to 2008), EMBASE (1985 to 2008) and reference lists of articles. Relevant conference proceedings were hand-searched and researchers in the field contacted.

SELECTION CRITERIA

Randomised controlled trials were included.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed eligibility and quality of trials.

MAIN RESULTS

For the update in 2008 five trials compared DET with SET. DET versus TET and DET versus FET were evaluated in a single small trial each. The difference in cumulative livebirth rates (CLBR) after DET and those after SET followed by transfer of a single frozen thawed embryo (1FZET) was not statistically significant (OR 0.81, 95% CI 0.59 to 1.11; p=0.18). There was no statistically significant difference in CLBR after a single fresh cycle of DET versus two fresh cycles of SET (OR 1.23, 95% CI 0.56 to 2.69, p= 0.60 ). The live birth rate (LBR) per woman in a single fresh treatment was higher following DET than SET (OR 2.10, 95% CI 1.65 to 2.66, p<0.00001). The MPR was lower following SET (OR 0.04, 95% CI 0.01 to 0.11; p< 0.00001). The CLBR following two fresh cycles of DET versus two fresh cycles of TET (OR 0.77, 95%CI 0.22 to 2.65, p=0.67) and CLBR after three fresh cycles of DET versus three fresh cycles of TET showed no statistically significant differences (OR 0.77, 95% CI 0.24 to 2.52; p=0.67). There were no statistically significant differences between DET and TET in terms of LBR (OR 0.40, 95%CI 0.09 to 1.85; p=0.24) and MPR (OR 0.17, 95%CI 0.01 to 3.85; p= 0.27). DET led to lower LBR than FET but the difference was not statistically significant (OR 0.35, 95% CI 0.11 to 1.05; p = 0.06).

AUTHORS' CONCLUSIONS

In a single fresh IVF cycle, SET is associated with a lower LBR than DET. However there is no significant difference in CLBR following SET+ 1FZET and the LBR following a single cycle of DET. MPR are lowered following SET compared with other transfer policies. There are insufficient data on the outcome of two versus three and four embryo transfer policies.

Addressing the growing problem of multiple gestations created by assisted reproductive therapies

Iatrogenic multiple pregnancy is the most significant complication of assisted reproductive technology (ART). Approximately half of all children born subsequent to ART result from a plural gestation. Furthermore, the majority of triplets and higher order births are the product of ART. The risks for multiple pregnancy vary with practice patterns and the techniques used to achieve pregnancy. Recognizing the potential for serious morbidity associated with multiple pregnancies, infertility specialists have developed strategies to reduce the complication of multiple pregnancies while maintaining acceptable pregnancy rates. Implementation of these refined practices has led to a reduction in the incidence of higher order multiple births, although the incidence of twins has yet to be minimized. Further reduction in the incidence of multiple births after ART necessitates a redefinition of success to emphasize the healthy singleton birth rate, rather than crude pregnancy rates.

Number of embryos for transfer following in-vitro fertilisation or intra-cytoplasmic sperm injection

BACKGROUND

The traditional reliance on the transfer of multiple embryos during in vitro fertilisation (IVF) in order to maximise the chance of pregnancy, has resulted in increasing rates of multiple pregnancies. Women undergoing IVF had a 20 - fold increased risk of twins and 400 - fold increased risk of higher order pregnancies (Martin 1998). The maternal and perinatal morbidity and mortality as well as national health service costs associated with multiple pregnancies is significantly high in comparison with singleton births (Luke 1992; Callahan 1994; Goldfarb 1996). Single embryo transfer is now being considered as an effective means of reducing this iatrogenic complication. This systematic review evaluates the effectiveness of elective two embryo transfer in comparison with single and more than two embryo transfer following IVF and ICSI (intra cytoplasmic sperm injection) treatment.

OBJECTIVES

The aim of this review is to determine, whether in couples who undergo IVF/ICSI: (1) the elective transfer of two embryos improves the probability of livebirth compared with: (a) Single embryo transfer, (b) Three embryo transfer or (c) Four embryo transfer.(2) the elective transfer of three embryos improves the probability of livebirth compared with: (a) Single embryo transfer, or (b) Four embryo transfer,

SEARCH STRATEGY

We searched the Cochrane Menstrual Disorders and Subfertility Group's trials register (searched June 2003), the Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 4, 2003), MEDLINE (1970 to 2003), EMBASE (1985 to 2003) and reference lists of articles. We also handsearched relevant conference proceedings and contacted researchers in the field.

SELECTION CRITERIA

Only randomised controlled trials were included.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed eligibility and quality of trials.

MAIN RESULTS

We found no studies that compared a policy of transferring multiple embryos on one cycle versus a policy of cryo- preservation and transfer of a single embryo over multiple cycles. We also found no trials comparing transfer of two versus three embryos. Three small, poorly reported trials compared transfer of two versus one embryo in a single cycle, and one small, poorly reported trial compared transfer of two versus four embryos in a single cycle. The clinical pregnancy rate per woman/couple associated with two embryo transfer was significantly higher compared to single embryo transfer (OR 2.08, 95% CI 1.24 to 3.50; test for overall effect p = 0.006). The live birth rate per woman/couple associated with two embryo transfer was also significantly higher than that associated with single embryo transfer (OR 1.90, 95% CI 1.12 to 3.22, test for overall effect p=0.02). The multiple pregnancy rate was significantly lower in women who had single embryo transfer (OR 9.97, 95% CI 2.61 to 38.19; p = 0.0008). The effectiveness of double embryo transfer versus four embryo transfer was tested in a single trial. There was no statistically significant differences in the clinical pregnancy rate (OR 0.75, 95% CI 0.26 to 2.16; p=0.6), and multiple pregnancy rates (OR 0.44. 95% CI 0.10 to 1.97; p = 0.28) between the two groups. The livebirth rate in the four embryo transfer group was higher compared to the two embryo transfer group, but the results were not statistically significant (OR 0.35, 95% CI 0.11 to 1.05; p = 0.06).

REVIEWERS' CONCLUSIONS

The results of this systematic review suggest that live birth and pregnancy rates following single embryo transfer are lower than those following double embryo transfer as are the chances of multiple pregnancy including twins. As such, it is unlikely that the conclusions are robust enough to catalyse a change in clinical practice. The studies included are limited by their small sample size, so that even large differences might be hidden. Cumulative livebirth rates are seldom reported. The data were inadequate to draw conclusions about single embryo transfer and first frozen single embryo transfer (1FZET) or subsequent single frozen embryo transfers. Until more evidence is available single embryo transfer may not be the preferred choice for all patients undergoing IVF/ICSI. Clinicians may need to individualise protocols for couples based on their risks of multiple pregnancy. A definitive pragmatic, large multi centre randomised controlled trial comparing single embryo versus double embryo transfer in terms of clinical and cost effectiveness as well as acceptability is required. The primary outcome measured should be cumulative livebirth per woman/couple.

Prevention of multiple pregnancies in an in vitro fertilization program

OBJECTIVE

To limit the high number of multiple pregnancies in an IVF program.

SETTING

In Vitro Fertilization Laboratory, Fertility Department, Public Hospital.

INTERVENTIONS

The number of embryos transferred was limited to two instead of three.

RESULTS

Limiting the number of embryos transferred to only two did not influence the take home baby rate but eliminated triplet and quadruplet gestations. Moreover, the number of patients with good quality supernumerary embryos available for cryopreservation increased.

CONCLUSIONS

To reduce the high frequency of multiple gestations in an IVF program, the number of embryos replaced should be limited to a maximum of two.

Cryopreservation of human embryos at the pronucleate, early cleavage, or expanded blastocyst stages

Supernumerary embryos following treatment by IVF or GIFT were cryopreserved at the pronucleate, early cleavage or expanded blastocyst stages. The success of embryo cryopreservation at these stages was evaluated in terms of (i) the proportion of embryos surviving the freeze/thaw procedure; (ii) the proportion of patients reaching embryo replacement; and (iii) the incidence of pregnancy per replacement. Significantly more embryos survived when frozen/thawed at the pronucleate (44/61; 72%) or early cleavage stages (48/80; 60%), than at the expanded blastocyst stage (13/34; 38%). A significantly higher proportion of patients had embryo replacements when embryos were frozen/thawed at the pronucleate (17/19; 89%) or early cleavage stages (21/24; 88%), than at the expanded blastocyst stage (9/17; 53%). Following replacement of frozen/thawed pronucleate and early cleavage stage embryos, clinical pregnancy rates of 8/17 (47%) and 3/21 (14%) clinical pregnancies were achieved, respectively. No pregnancies were achieved following replacement of frozen/thawed expanded blastocysts.

An obstetric analysis of fifty consecutive pregnancies after transfer of cryopreserved human embryos

This report describes the obstetric outcome in 50 pregnancies resulting from the transfer of human embryos that had been cryopreserved for up to 2 years. The duration of cryopreservation did not influence the pregnancy rate after thawed embryo transfer. Thirty-one babies have been born from 28 pregnancies and a further seven pregnancies are currently in the second and third trimesters. Twenty-eight percent of the pregnancies failed to progress beyond the first trimester. One pregnancy was terminated at 22 weeks' gestation because of severe fetal malformation. Important antenatal events included premature uterine activity in six patients although only one patient with a singleton pregnancy ultimately was delivered prematurely. Retroplacental hemorrhage occurred in four patients but was of clinical consequence in only one. There was a high incidence of breech presentation at term in singleton pregnancies (12%). The cesarean section rate in this series was 21%. An international registry of cryopreserved pregnancies would facilitate data collection in this relatively new clinical field.