Association of extended culture to blastocyst and pre-malignant gestational trophoblastic disease risk following IVF/ICSI-assisted reproduction cycles: an analysis of large UK national database

PURPOSE

To assess whether there is an association between extended in vitro culture based on embryo developmental stage at transfer and pre-malignant gestational trophoblastic disease (GTD) risk of molar pregnancy during assisted reproduction.

METHODS

A retrospective study was carried out using Human Fertilization and Embryology Authority (HFEA) anonymized register from 1999 to 2016. A total of 540,376 cycles were eligible to be included in the study after excluding any kind of donor treatment or surrogacy, frozen embryo transfers, and cycles with incomplete data. Subgroup analysis was carried out in subjects with primary infertility aiming to exclude an increased risk in those with a previous GTD. Multivariate logistic regression analysis was used to adjust for possible confounders, and the effect of day of embryo transfer in IVF (in vitro fertilization)/ICSI (intracytoplasmic sperm injection) treatment on a molar pregnancy GTD outcome was analyzed.

RESULTS

The prevalence of a molar pregnancy GTD among the study population was 3.4/10,000 livebirths (53/156,683) with a higher risk in the over 40 age category. No significant difference of pre-malignant GTD incidence was seen between IVF and ICSI (0.01% vs 0.009% respectively). No association was seen with GTD based on type/cause of infertility or number of embryos transferred. Crude (1.06; 95% CI 0.852-1.31) and adjusted (1.07; 95% CI (0.857-1.32) odds ratios were calculated to see an association between day of embryo transfer and the occurrence of a GTD. There was no association between day of embryo transfer and molar GTD risk after adjusting for age and secondary infertility.

CONCLUSION

No significant association between pre-malignant molar gestational trophoblastic disease and extended in vitro embryo culture was found after analyzing 540,376 cycles of IVF and ICSI.

P–770 Two in One - Monozygotic splitting and associated perinatal outcomes after oocyte freezing; an exploratory analysis of the UK national database from 1990 to 2016

Study question

Is oocyte freezing a risk factor for monozygotic splitting?

Summary answer

There is a trend towards a higher monozygotic splitting incidence among frozen oocytes, but this did not reach statistical significance.

What is known already

Laboratory techniques which involve embryo manipulation such as ICSI, assisted hatching, embryo biopsy for pre-implantation genetic testing and extended culture to the blastocyst stage appear to increase the risk of monozygotic splitting. Whilst there is some data that embryo freezing does not appear to increase the risk of monozygotic splitting, there is no comparable analysis on whether oocyte freezing increases the risk of monozygotic splitting.

Study design, size, duration

This was a retrospective cohort study analysing 988 015 ART (assisted reproductive technique) cycles from the HFEA anonymised database from 1990 to 2016. As frozen oocytes require ICSI, only fresh oocytes with ICSI were taken for comparison and frozen embryo transfers were excluded. Only single embryo transfers were included.[CM1] [MM2] We also noted ages of the female partner at the time of treatment, stage of embryo transfer, and whether pre-implantation genetic testing had been performed.

Participants/materials, setting, methods

There were 84 085 ICSI cycles with single embryo transfers using fresh oocytes and 596 using frozen oocytes. Monozygotic splitting was defined as the presence of two foetal hearts [CM1] [MM2] on ultrasound. Live birth (LB)was defined as either a singleton or a twin LB resulting from a monozygotically split embryo. Preterm birth (PTB) was defined as birth prior to 37 weeks gestation and early PTB as birth prior to 32 weeks gestation.

Main results and the role of chance

The frozen oocyte group had fewer women in the under–35 age group (frozen oocytes 16.6% vs fresh oocytes 53.6%, p < 0.0001) and a higher proportion of blastocyst transfers ( frozen oocytes 55.1% vs fresh oocytes 48.8%, p = 0.002) There were only 10 PGT cycles amongst monozygotically split embryos from fresh oocytes in our analysis, and none in the frozen oocyte group. Hence, this was not included as a confounder. There was a non-significant trend toward a higher incidence of monozygotic splitting amongst frozen oocytes (4/596, 2.3%, all monozygotic twins) than amongst fresh oocytes (378/27 019, 1.4%, 372 monozygotic twins and 6 monozygotic triplets); OR 1.688, 95% CI 0.623 to 4.574 and aOR 1.506, 95% CI 0.531 to 4.274 (maternal age and stage of embryo transfer adjusted as confounders). Of the 378 monozygotically split embryos from fresh oocytes, 308 (81.5%) had a LB: of which 47 (15.3%) were singletons and the rest were twins; 241 (78.2%) were PTB and 56 (18.2%) were early PTB. Of the four monozygotic twins from frozen oocytes, all reached a LB; one was a singleton term LB (Birthweight 3–3.5kg) whilst three were twin preterm LBs at 35–36 weeks, with no early PTBs and twin median birthweight 2–2.5 kg.

Limitations, reasons for caution

Albeit a large national database, this cohort study was restricted due to absence of data on potential confounders such as age at oocyte freezing, method of cryopreservation and length of storage.[CM1] Data was also lacking on amnionicity, obstetric risks including pre-eclampsia, twin-to-twin-transfusion syndrome, intrapartum and late effects.

Wider implications of the findings: With rapid rise in egg freezing, our findings would help reassure women that eggs on ice does not predispose to significant risk of two-in-one monozygotic splitting. However, the marginal trend (from 1.4% in fresh to 2.3% in frozen oocytes), does indicate that this subject merits further research.

Trial registration number

Not applicable. A database based retrospective study