Embryo freezing to prevent ovarian hyperstimulation syndrome

Ovarian Hyperstimulation Syndrome (OHSS) requiring Intensive Care Unit (ICU) admission between 1996-2020 in England, Wales, and Northern Ireland

Introduction

Ovarian Hyperstimulation Syndrome (OHSS) is a life-threatening iatrogenic complication of In vitro fertilisation (IVF). This study aimed to quantify rates of Ovarian Hyperstimulation Syndrome (OHSS) requiring intensive care unit (ICU) admission and assess whether trends have changed between 1996-2020 commensurate with the introduction of safer IVF practices.

Methods

Data regarding Intensive Care Unit (ICU) admission across England, Wales and Northern Ireland was gathered retrospectively from the Intensive Care National Audit and Research Centre (ICNARC) database. 38,957 female patients aged between 18-55 years were admitted to ICU for OHSS or related conditions between 1996-2020. The primary outcome was the rate of OHSS requiring ICU admission expressed as a proportion of the number of fresh IVF cycles conducted in that year according to Human Fertility and Embryology Authority (HFEA) records. Baseline characteristics (for example, age, ethnicity, BMI), biochemical parameters (such as renal function, serum electrolytes), length of ICU stay and duration and need for organ support, were also compared between ICU patients with 'confirmed OHSS' and those 'without OHSS'.

Results

There were 238 cases of 'confirmed OHSS' requiring ICU admission recorded between 1996-2020. Rates of OHSS requiring ICU admission declined over the study period (P=0.006); the annual rate of severe OHSS requiring intensive care admission halved when comparing those occurring between 1996-2007 and 2008-2020 (OR=0.37, 95% CI 0.37-0.45; P<0.0001). Patients spent a mean of 3.5 days in the ICU, with 86.3% of patients with 'confirmed OHSS' requiring at least 2 days of higher level (i.e., level 2 or 3) care. Patients with 'confirmed OHSS' required a shorter duration of renal, advanced cardiovascular, and advanced respiratory support than patients 'without OHSS' (P<0.0001 for all comparisons). There was no significant difference in BMI or ethnicity between those with 'confirmed OHSS' and those 'without OHSS', however women with 'confirmed OHSS' were younger (34 versus 41 years old, p<0.0001).

Discussion

Although absolute rates of OHSS requiring ICU admission recorded in this study are likely to represent a significant underestimate of all clinically significant OHSS, rates of OHSS requiring ICU admission have decreased since 1996 in concordance with the introduction of modern IVF practices.

Blastocyst-stage versus cleavage-stage embryo transfer in the first frozen cycles of OHSS-risk patients who deferred from fresh embryo transfer

Elective cryopreservation of all embryos has been the most effective means to avoid developing ovarian hyperstimulation syndrome (OHSS). However, it is still unknown which stage is optimal for freezing and transferring into uterus in OHSS-risk patients. This study was undertaken to evaluate whether OHSS-risk patients could benefit from transferring blastocysts. A total of 162 women were allocated to cleavage-stage embryo transfer (ET) (group A = 70) and blastocysts transfer (group B = 92) on the basis of patients' voluntary in their first frozen cycles. Although the mean number of transferred embryos in group A was significantly more than those in group B (2.37 ± 0.52 versus 2.11 ± 0.52, p < 0.05), the clinical pregnancy rates, implantation rates and live birth rates in group B were significantly higher than those in group A (47.83% versus 31.43%, p < 0.05; 31.44% versus 18.67%, p < 0.05; 40.21% versus 27.14%, p < 0.05), and the multiple pregnancy rates in both groups were comparable (34.09% versus 36.36%, p > 0.05). The observed results in OHSS-risk population allow us to take a position in favor of blastocyst transfer, thus pregnancy and live birth could be achieved with fewer ETs and in a shorter time frame.

[Ovarian stimulation monitoring: past, present and perspectives]

Since the inception of Assisted Reproductive Technology (ART), knowing the moment of ovulation has always been a priority. Initially, the monitoring was accomplished by observing the luteinizing hormone (LH) surge just before ovulation. Currently, in all ART facilities, the monitoring of all stimulated ovulatory cycles is done by using the conventional two-dimensional (2D) ultrasound to measure follicle diameter and by drawing blood tests that measure estradiol, progesterone, and luteinizing hormone levels. These exams allow determination of the numbers and quality of growing ovarian follicles and evaluation of follicle maturity before choosing the appropriate time for ovulation triggering. The monitoring of ovulatory cycles has now become enhanced with the arrival of new software called SonoAVC. This software allows the utilization of 3D blocks to immediately calculate the total number and volume of the follicles inside the ovary. This automatic approach is faster, precise, and more efficient. It also has better reproducibility than the classical 2D diameters. Furthermore, certain ART professionals envision that by using the SonoVac technology, patients will no longer need to be monitored with regular ultrasounds and with systematic hormonal testing.

Ovarian hyperstimulation syndrome: steps to maximize success and minimize effect for assisted reproductive outcome

OBJECTIVE

To investigate the strategies used to decrease the risk of ovarian hyperstimulation syndrome (OHSS) and their impact on pregnancy and live birth rates.

DESIGN

Retrospective cohort analysis.

SETTING

University hospital.

PATIENT(S)

One hundred eighty-eight patients undergoing fresh in vitro fertilization (IVF) cycles between 2000 and 2004, with peak serum estradiol levels >2500 pg/mL and presumed to be at risk for OHSS.

INTERVENTION(S)

Coasting and elective embryo cryopreservation were evaluated for their effect on OHSS and live birth rates.

MAIN OUTCOME MEASURE(S)

Pregnancy, live birth rates, and OHSS incidence.

RESULT(S)

Out of 188 patients at risk for OHSS, 21 patients had their cycles coasted (group 1), and elective embryo cryopreservation was performed in 32 patients (group 2). In 135 patients with no other risk factors, ovulation was triggered with human chorionic gonadotropin and embryo transfer was performed (group 3). The incidence in our IVF population was 38 out of 1002 (3.8%). The overall incidence of OHSS for those who had an estradiol level >2500 pg/mL was 20.2% (38 out of 188), and none of the patients in group 1 developed OHSS; 13 out of 32 patients in group 2 (40.6%) and 25 out of 135 (18.5%) patients in group 3 developed OHSS. The live birth rate was 38%, 40%, and 45% in groups 1, 2, and 3, respectively, and the cumulative live birth rate was 52%, 75%, and 59%, respectively.

CONCLUSION(S)

Elective cryopreservation of embryos with subsequent frozen embryo transfer and coasting are effective ways of maximizing pregnancy and limiting severe OHSS.

Coasting vs. cryopreservation of all embryos for prevention of ovarian hyperstimulation syndrome in in vitro fertilization

In the patient at risk for ovarian hyperstimulation syndrome, coasting will result in fewer eggs retrieved and embryos produced when compared with cryopreservation of all embryos. However, both strategies are associated with a similar incidence of ovarian hyperstimulation syndrome, with achievement of comparable cumulative pregnancy rates.

Lysed cell removal promotes frozen–thawed embryo development

OBJECTIVE

To develop a mouse model to investigate the possible causes for increased success rates when lysed cells are removed from thawed embryos.

DESIGN

Experimental study.

SETTING

Clinical IVF laboratory.

INTERVENTION(S)

Assisted hatching, cell lysis, and removal of lysed cells.

MAIN OUTCOME MEASURE(S)

Embryonic growth rate and morphology.

RESULT(S)

The mouse embryos were divided into three groups; control (no cell lysis), group 1 (cell lysis and removal), and group 2 (cell lysis only). There was no significant difference in the initial number of blastomeres in each group or the number of cells lysed artificially in groups 1 and 2. The rate of embryonic development showed a significant delay in group 2 (7.97 +/- 4.92; control, 10.42 +/- 8.18; group 1, 5.74 +/-4.42; group 2). The embryo morphology on day 4 was significantly improved in group 1 and the control group when compared with group 2.

CONCLUSION(S)

Mouse embryos with artificially lysed cells after thawing had poorer developmental quality and growth rates compared with control embryos. However, removal of lysed cells restored the embryo's developmental potential to that of the control. Cell number and morphology was also significantly improved compared with embryos without lysed cell removal. These findings are consistent with human embryo development after thawing when lysed cells are present and thus mechanical lysis seems to be an appropriate method by which to further study frozen-thawed lysed cell removal.

Removal of lysed blastomeres from frozen–thawed embryos improves implantation and pregnancy rates in frozen embryo transfer cycles

OBJECTIVE

To evaluate the effect of degenerated (lysed) blastomere removal on implantation and pregnancy rates in cleavage-stage cryo-embryo transfer (ET) cycles.

DESIGN

Randomized clinical trial.

SETTING

Private reproductive medical center.

PATIENT(S)

A total of 88 patients who received frozen-thawed ET, divided into two groups.

INTERVENTION(S)

Embryo freezing and thawing; opening of the zona pellucida and removal of cryodamaged blastomeres (in the study group), followed by same-day ET.

MAIN OUTCOME MEASURE(S)

Extent of survival of cleavage-stage embryos after the freeze-thaw procedure; embryo implantation and clinical pregnancies.

RESULT(S)

Oocyte number per patient, fertilization rate, embryo development rate (and quality), and freezing rates were similar in the two groups in the fresh cycle. In the control group, a total of 55 embryos (25%) of the 217 thawed remained fully intact, and 53 (26%) of the 207 in the study group remained intact. The average number of embryos transferred per group was similar (control, 3.4 +/- 0.9; study, 3.3 +/- 0.9). Implantation rates were 12% and 26% in the control and study groups, respectively. The clinical pregnancy rate was 23% in the control group and 64% in the study group when lysed cell removal was performed.

CONCLUSION(S)

The results show that pregnancy and implantation rates are higher in the study group; therefore, the removal of degenerated blastomeres may be beneficial to all patients who undergo cleavage-stage, frozen-thawed ET.