Risk of preterm birth after blastocyst embryo transfer: a large population study using contemporary registry data from Australia and New Zealand

The impact of reference growth standards on small- and large-for-gestational age outcomes among pregnancies conceived by fresh and frozen embryo transfers

Objective

To describe differences in the frequency of small-for-gestational age (SGA) and large-for-gestational age (LGA) driven by different birth weight curves in assisted reproductive technology (ART)-conceived pregnancies.

Design

Retrospective cohort study.

Setting

Single academic medical center.

Patients

Singleton live births between the gestational ages of 36 weeks and 0 days and 42 weeks and 6 days from fresh or frozen embryo transfer (ET).

Interventions

None.

Main Outcome Measures

SGA (<10th percentile) and LGA (>90th percentile) classified by Fenton, INTERGROWTH-21, World Health Organization, Duryea, and Oken curves.

Results

The median birth weight and gestational age at birth among fresh ET pregnancies were 3,289g (interquartile range [IQR], 2,977-3,600g) and 39.4 (IQR, 38.6-40.3) weeks, respectively, and those among frozen ET pregnancies were 3,399g (IQR, 3,065-3,685g) and 39.4 (IQR, 38.7-40.1) weeks, respectively. The frequencies of SGA neonates using each birth weight standard ranged from 5.8% to 13.4% for fresh ET and from 3.5% to 8.7% for frozen ET. Those of LGA neonates ranged from 5.3% to 14.3% for fresh ET and from 6.6% to 21.2% for frozen ET.

Conclusion

The frequency of SGA and LGA neonates among ART-conceived gestations is partially driven by the birth weight standard. Selecting an appropriate standard that best reflects the patient population is critical to quantifying the risk of ART-conceived pregnancies.

No major differences in perinatal and maternal outcomes between uninterrupted embryo culture in time-lapse system and conventional embryo culture

STUDY QUESTION

Is embryo culture in a closed time-lapse system associated with any differences in perinatal and maternal outcomes in comparison to conventional culture and spontaneous conception?

SUMMARY ANSWER

There were no significant differences between time-lapse and conventional embryo culture in preterm birth (PTB, <37 weeks), low birth weight (LBW, >2500 g) and hypertensive disorders of pregnancy for singleton deliveries, the primary outcomes of this study.

WHAT IS KNOWN ALREADY

Evidence from prospective trials evaluating the safety of time-lapse incubation for clinical use show similar embryo development rates, implantation rates, and ongoing pregnancy and live birth rates when compared to conventional incubation. Few studies have investigated if uninterrupted culture can alter risks of adverse perinatal outcomes presently associated with IVF when compared to conventional culture and spontaneous conceptions.

STUDY DESIGN, SIZE, DURATION

This study is a Swedish population-based retrospective registry study, including 7379 singleton deliveries after fresh embryo transfer between 2013 and 2018 from selected IVF clinics. Perinatal outcomes of singletons born from time-lapse-cultured embryos were compared to singletons from embryos cultured in conventional incubators and 71 300 singletons from spontaneous conceptions. Main perinatal outcomes included PTB and LBW. Main maternal outcomes included hypertensive disorders of pregnancy (pregnancy hypertension and preeclampsia).

PARTICIPANTS/MATERIALS, SETTING, METHODS

From nine IVF clinics, 2683 singletons born after fresh embryo transfer in a time-lapse system were compared to 4696 singletons born after culture in a conventional incubator and 71 300 singletons born after spontaneous conception matched for year of birth, parity, and maternal age. Patient and treatment characteristics from IVF deliveries were cross-linked with the Swedish Medical Birth Register, Register of Birth Defects, National Patient Register and Statistics Sweden. Children born after sperm and oocyte donation cycles and after Preimplantation Genetic testing cycles were excluded. Odds ratio (OR) and adjusted OR were calculated, adjusting for relevant confounders.

MAIN RESULTS AND THE ROLE OF CHANCE

In the adjusted analyses, no significant differences were found for risk of PTB (adjusted OR 1.11, 95% CI 0.87-1.41) and LBW (adjusted OR 0.86, 95% CI 0.66-1.14) or hypertensive disorders of pregnancy; preeclampsia and hypertension (adjusted OR 0.99, 95% CI 0.67-1.45 and adjusted OR 0.98, 95% CI 0.62-1.53, respectively) between time-lapse and conventional incubation systems. A significantly increased risk of PTB (adjusted OR 1.31, 95% CI 1.08-1.60) and LBW (adjusted OR 1.36, 95% CI 1.08-1.72) was found for singletons born after time-lapse incubation compared to singletons born after spontaneous conceptions. In addition, a lower risk for pregnancy hypertension (adjusted OR 0.72 95% CI 0.53-0.99) but no significant difference for preeclampsia (adjusted OR 0.87, 95% CI 0.68-1.12) was found compared to spontaneous conceptions. Subgroup analyses showed that some risks were related to the day of embryo transfer, with more adverse outcomes after blastocyst transfer in comparison to cleavage stage transfer.

LIMITATIONS, REASONS FOR CAUTION

This study is retrospective in design and different clinical strategies may have been used to select specific patient groups for time-lapse versus conventional incubation. The number of patients is limited and larger datasets are required to obtain more precise estimates and adjust for possible effect of additional embryo culture variables.

WIDER IMPLICATIONS OF THE FINDINGS

Embryo culture in time-lapse systems is not associated with major differences in perinatal and maternal outcomes, compared to conventional embryo culture, suggesting that this technology is an acceptable alternative for embryo incubation.

STUDY FUNDING/COMPETING INTEREST(S)

The study was financed by a research grant from Gedeon Richter. There are no conflicts of interest for all authors to declare.

TRIAL REGISTRATION NUMBER

N/A.

Congenital anomaly and perinatal outcome following blastocyst- vs cleavage-stage embryo transfer: systematic review and network meta-analysis

OBJECTIVES

To compare the reported rate of any congenital anomaly and perinatal outcome of pregnancy following blastocyst- vs cleavage-stage embryo transfer using a pairwise meta-analysis and to evaluate the same outcomes following fresh-blastocyst, frozen-blastocyst, fresh-cleavage or frozen-cleavage embryo transfer using a network meta-analysis.

METHODS

A literature search was performed in PubMed, Scopus and CENTRAL and registers for ongoing studies, from inception to February 2022, for randomized controlled trials (RCTs) with any sample size and observational studies including at least 100 live births per group, comparing the rates of any congenital anomaly and perinatal outcome of pregnancy following fresh/frozen embryo transfer at cleavage (day 2-3) vs blastocyst (day 5-7) stage. Risk ratios (RRs) along with their 95% CIs were pooled via a random-effects model meta-analysis. Within a frequentist network meta-analysis framework, outcomes of all four treatment modalities (i.e. fresh-blastocyst, fresh-cleavage, frozen-blastocyst, frozen-cleavage) were compared further. Any congenital anomaly constituted the primary outcome, whereas preterm delivery (delivery < 37 weeks), low birth weight (LBW; < 2500 g), gender of the neonate (male), perinatal death and healthy neonate (defined as liveborn neonate, delivered at term, weighing ≥ 2500 g, surviving for at least 28 days postbirth and without any congenital anomaly) were considered as secondary outcomes. Subgroup analyses by plurality (liveborn singleton vs multiple pregnancy) were conducted in the pairwise and network meta-analyses. The risk of bias was assessed using the RoB2 tool for RCTs and the ROBINS-I tool for non-randomized studies. Certainty of evidence was assessed using GRADE.

RESULTS

Through the literature search, 550 studies were retrieved and 33 were included in the systematic review. We found no significant difference in the risk for any congenital anomaly between blastocyst- and cleavage-stage transfer (RR, 0.80 (95% CI, 0.63-1.03); 10 studies; n = 192 442; I²  = 85.5%). An increased probability of a male neonate was observed following blastocyst- vs cleavage-stage transfer (RR, 1.07 (95% CI, 1.06-1.09); 18 studies; n = 227 530; I²  = 32.7%). No significant differences in other secondary outcomes or significant subgroup differences between liveborn singletons and multiple pregnancies were observed. The network meta-analysis showed a significantly lower risk for LBW following frozen-blastocyst vs fresh-blastocyst (RR, 0.76 (95% CI, 0.60-0.95)) or fresh-cleavage (RR, 0.74 (95% CI, 0.59-0.93)) transfer. Frozen-blastocyst transfer was associated with an increased risk for perinatal death compared with the fresh-cleavage method (RR, 2.06 (95% CI, 1.10-3.88)). The higher probability of a male neonate following blastocyst transfer remained evident in the network comparisons. All outcomes were assessed to be of very-low certainty of evidence.

CONCLUSIONS

Current very-low certainty of evidence shows that there may be little-to-no difference in the risk for congenital anomaly or adverse perinatal outcome of pregnancy following blastocyst- vs cleavage-stage embryo transfer, although there was a slightly increased probability of a male neonate following blastocyst transfer. When considering cryopreservation, frozen-blastocyst transfer was associated with a reduction in the risk for LBW compared with both fresh-transfer modalities, and fresh-cleavage transfer may be associated with a reduction in the risk for perinatal death compared with frozen-blastocyst transfer. High-quality RCTs with separate data on fresh and frozen cycles and consistent reporting of culture conditions and freezing methods are mandatory. Individual participant data meta-analyses are required to address the substantial inconsistency resulting from current aggregate data approaches. © 2022 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Clinical analysis on the influencing factors related to preterm twin pregnancy

OBJECTIVE

The aim of this study was to explore the influencing factors of preterm twin pregnancy.

METHODS

In total, 602 twin-pregnant women delivered from February 2016 to February 2020 were analyzed retrospectively. According to whether the pregnant women were preterm or not, they were divided into preterm group (n=363) and term group (n=239). Baseline information, such as maternal age, address, and education level of the pregnant women, were collected. The clinical information of pregnant women, such as chorionic, preeclampsia, gestational diabetes, premature rupture of membranes, abnormal fetal position, and fetal weight, were analyzed. Logistic regression analysis was used to analyze the risk factors. p-value <0.05 was considered statistically significant.

RESULTS

In the preterm group, monochorionic diamniotic comorbidities were significantly higher compared with the control group (p<0.05). Higher risks of preterm group have lower education (p<0.05). Multiple logistic regression analysis demonstrated that education, preeclampsia, and premature rupture of membranes were risk factors for preterm twin pregnancy.

CONCLUSIONS

Preterm birth in twin pregnancy is associated with many risk factors, such as education, preeclampsia, and premature rupture of membranes. Pregnancy supervision and prenatal guidance for twin pregnancy should be strengthened. Furthermore, early detection and diagnosis of comorbidities can improve maternal and neonatal outcomes.

Comparison of perinatal outcomes after frozen or fresh embryo transfer: separate analyses of singleton, twin, and sibling live births from a linked national in vitro fertilization registry

OBJECTIVE

To determine whether perinatal outcomes following frozen vs. fresh embryo transfer (ET) differ within singletons, within sets of twins, and between siblings.

DESIGN

Population-based retrospective cohort study.

SETTING

Academic Medical School PATIENT(S): 200,075 live births in 151,561 women who underwent in vitro fertilization with frozen or fresh ET between 1992 and 2017.

MAIN OUTCOME MEASURE(S)

Gestational age at birth, birthweight, congenital anomaly, and healthy baby (≥37 weeks of gestation, birthweight 2,500-4,000 g, no congenital malformations).

RESULT(S)

There were 200,075 live births in 151,561 women including 132,679 singletons, 33,698 sets of twins, and 5,723 pairs of singleton siblings. In singletons, frozen ET was associated with a lower risk of very preterm birth (adjusted relative risk [aRR], 0.83; 95% confidence interval [CI], 0.73, 0.94), preterm birth (aRR, 0.93; 95% CI, 0.88, 0.97), low birthweight (<2,500 g) (aRR, 0.72; 95% CI, 0.68, 0.77), small for gestational age (aRR, 0.66; 95% CI, 0.62, 0.70) and congenital anomaly (aRR, 0.85; 95% CI, 0.78, 0.94), but higher risk of high birthweight (>4,000 g) (aRR, 1.64; 95% CI, 1.58, 1.72) and large for gestational age (aRR, 1.62; 95% CI, 1.55, 1.70) in comparison with fresh ET. In twins, frozen ET was associated with lower risk of very preterm birth (aRR, 0.84; 95% CI, 0.73, 0.97), and low birthweight (aRR, 0.72; 95% CI, 0.68, 0.77), but with a higher chance of a healthy baby (aRR, 1.11; 95% CI, 1.06, 1.16) compared to fresh ET. Singletons conceived following frozen ET had a lower risk of low birthweight (aRR, 0.56; 95% CI, 0.44, 0.74) and being small for gestational age (aRR, 0.54; 95% CI, 0.42, 0.68) than a singleton sibling born after a fresh ET. Frozen ET also was associated with higher risk of high birthweight (aRR, 1.85; 95% CI, 1.54, 2.24) and being large for gestational age (aRR, 1.81; 95% CI, 1.50, 2.20), and also were less likely to be preterm (aRR, 0.81; 95% CI, 0.67, 0.99).

CONCLUSION(S)

Our key finding is that singletons born following a frozen ET are less likely to be small for gestational age than a singleton sibling born following fresh ET but are more likely to be large for gestational age.

Perinatal outcomes of singletons born after blastocyst or cleavage-stage embryo transfer in FET cycles

PURPOSE

To compare perinatal outcomes of singletons after blastocyst versus cleavage-stage embryo transfer in frozen-thawed embryo transfer (FET) cycles.

METHODS

This was a retrospective cohort study of 4835 women who conceived after frozen-thawed embryo transfer and delivered a singleton baby from January 2015 to March 2020. The perinatal outcomes of the singletons born after blastocyst transfer (N = 3364) were compared to the singletons born after cleavage-stage transfer (N = 1471), including gestational week, birth weight, newborn gender and Apgar score.

RESULTS

Univariate and multivariate analysis found that infants born after blastocyst transfer had a higher risk of preterm birth (PTB) [adjusted odds ratio (aOR) 1.480; 95% confidence interval (CI) 1.213-1.807], large for gestational age (LGA) (aOR 1.329, 95%CI 1.149-1.536) and very large for gestational age (VLGA) (aOR 1.317, 95%CI 1.092-1.590) compared to infants born after cleavage-stage embryo transfer. When categorized by gestational weeks, the proportion of LGA was significantly higher for boys born after BT between GW 37 to 41 (aOR 1.301, 95%CI 1.051-1.609) and for girls born after BT between GW 32 to 41 (aOR 2.690, 95%CI 1.154-6.271, aOR 1.377, 95%CI 1.094-1.733), compared to boys and girls born after CT.

CONCLUSION

Our data suggested that the risk of PTB and LGA increased after blastocyst transfer versus cleavage-stage embryo transfer in FET cycles, and the risk of LGA is more apparent in the last trimester of pregnancy. Further studies are needed to confirm our findings and explored the association between the extended embryo culture and long-term outcomes of offspring.

Prenatal growth trajectories and birth outcomes after frozen-thawed extended culture embryo transfer and fresh embryo transfer: the Rotterdam Periconception Cohort

RESEARCH QUESTION

Are there differences in prenatal growth trajectories and birth outcomes between singleton pregnancies conceived after IVF treatment with frozen-thawed extended culture embryo transfer at day 5, fresh embryo transfer at day 3 or naturally conceived pregnancies?

DESIGN

From a prospective hospital-based cohort, 859 singleton pregnancies were selected, including 133 conceived after IVF with frozen-thawed embryo transfer, 276 after fresh embryo transfer, and 450 naturally conceived pregnancies. Longitudinal 3D ultrasound scans were performed at 7, 9 and 11 weeks of gestation for offline crown-rump length (CRL) and embryonic volume measurements. Second trimester estimated fetal weight was based on growth parameters obtained during the routine fetal anomaly scan at 20 weeks of gestation. Birth outcome data were collected from medical records.

RESULTS

No differences regarding embryonic growth trajectories were observed between frozen-thawed and fresh embryo transfer. Birthweight percentiles after fresh embryo transfer were lower than after frozen-thawed embryo transfer (38.0 versus 48.0; P = 0.046, respectively). The prevalence of non-iatrogenic preterm birth (PTB) was significantly lower in pregnancies resulting from fresh embryo transfer compared with frozen-thawed embryo transfer (4.7% versus 10.9%; P = 0.026, respectively). Compared with naturally conceived pregnancies, birthweight percentiles and percentage of non-iatrogenic PTB were significantly lower in pregnancies after fresh embryo transfer and gestational age at birth was significantly higher.

CONCLUSIONS

This study shows that embryonic growth is comparable between singleton pregnancies conceived after fresh and frozen-thawed embryo transfer. The lower relative birthweight and PTB rate in pregnancies after fresh embryo transfer than after frozen-thawed embryo transfer and naturally conceived pregnancies warrants further investigation.

Perinatal and obstetric outcomes in singleton pregnancies following fresh versus cryopreserved blastocyst transfer: a meta-analysis

The transfer of cryopreserved blastocysts is increasing in IVF centres. However, little is known about the perinatal and obstetric outcomes of this procedure. In an attempt to further elucidate these issues, a systematic review and meta-analysis was conducted to compare cryopreserved transfer with fresh blastocyst embryo transfer. The results show that the risk of both preterm (odds ratio [OR] 0.89, 95% confidence interval [CI] 0.80-0.99, P = 0.04) and low birthweight births (OR 0.82, 95% CI 0.68-0.99, P = 0.04) was significantly lower after cryopreserved blastocyst transfer than after fresh blastocyst transfer. The rate of large for gestational age births was significantly higher (OR 1.68, 95% CI 1.55-1.82, P < 0.00001) and the rate of small for gestational age births significantly lower (OR 0.59, 95% CI 0.54-0.65, P < 0.00001) after cryopreserved blastocyst transfer. The transfer of cryopreserved blastocysts was associated with a significantly lower risk of placental abruption (OR 0.58, 95% CI 0.40-0.83, P = 0.003) but a significantly higher risk of Caesarean section (OR 1.21, 95% CI 1.01-1.43, P = 0.03). In conclusion, the perinatal and obstetric outcomes associated with the transfer of cryopreserved blastocysts differ from those associated with fresh blastocyst transfer.

Perinatal outcomes in singleton live births after fresh blastocyst-stage embryo transfer: a retrospective analysis of 67 147 IVF/ICSI cycles

STUDY QUESTION

Are perinatal outcomes different between singleton live births conceived from fresh blastocyst transfer and those following the transfer of fresh cleavage-stage embryos?

SUMMARY ANSWER

Fresh blastocyst transfer does not increase risks of preterm birth (PTB), low/high birth weight or congenital anomaly and does not alter the sex ratio at birth or prejudice the chance of having a healthy baby.

WHAT IS KNOWN ALREADY

Extended embryo culture is currently considered the best option for embryo selection, but concerns have been raised about increased risks of preterm delivery and large-for-gestational-age (LGA) babies.

STUDY DESIGN, SIZE, DURATION

We conducted a retrospective cohort study based on data from the Human Fertilisation and Embryology Authority (HFEA) anonymised and cycle-based dataset in the UK between 1999 and 2011.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Baseline characteristics were compared between in vitro fertilisation (IVF)/intracytoplasmic sperm injection (ICSI) blastocyst-stage and cleavage-stage embryo transfer cycles using the χ2 test for categorical/dichotomised covariates and the Mann-Whitney test for continuous covariates. Statistical significance was set at <0.005. Poisson regression and multinomial logistic regression were used to establish relationships between perinatal outcomes and blastocyst-stage embryo transfer or cleavage-stage embryo transfer. Risk ratios (RRs), adjusted risk ratios (aRRs) and their 99.5% confidence intervals (CIs) were calculated as a measure of strength of associations. Results were adjusted for clinically relevant covariates. A sub-group analysis included women undergoing their first IVF/ICSI treatment. The level of significance was set at <0.05, and 95% CIs were calculated in the sub-group analysis.

MAIN RESULTS AND THE ROLE OF CHANCE

Of a total of 67 147 IVF/ICSI cycles, 11 152 involved blastocyst-stage embryo(s) and 55 995 involved cleavage-stage embryo(s). The two groups were comparable with regards to the risk of PTB (aRR, 1.00; 99.5% CI, 0.79-1.25), very-preterm birth (VPTB) (aRR, 1.00; 99.5% CI, 0.63-1.54), very-low birth weight (VLBW) (aRR, 0.84; 99.5% CI, 0.53-1.34), low birth weight (LBW) (aRR, 0.92; 99.5% CI, 0.73-1.16), high birth weight (HBW) (aRR, 0.94; 99.5% CI, 0.75-1.18) and very-high birth weight (VHBW) (aRR, 1.05; 99.5% CI, 0.66-1.65). The risk of congenital anomaly was 16% higher in the blastocyst-stage group than in the cleavage-stage group, but this was not statistically significant (aRR, 1.16; 99.5% CI, 0.90-1.49). The chance of having a healthy baby (born at term, with a normal birth weight and no congenital anomalies) was not altered by extended culture (aRR, 1.00; 99.5% CI, 0.93-1.07). Extended culture was associated with a marginal increase in the chance having a male baby in the main cycle-based analysis (aRR, 1.04; 99.5% CI, 1.01-1.09) but not in the sub-group analysis of women undergoing their first cycle of treatment (aRR, 1.04; 95% CI, 1.00-1.08). In the sub-group analysis, the risk of congenital anomalies was significantly higher after blastocyst-stage embryo transfer (aRR, 1.42; 95% CI, 1.12-1.81).

LIMITATIONS, REASONS FOR CAUTION

This study is limited by the use of observational data and inability to adjust for key confounders, such as maternal smoking status and body mass index (BMI), which were not recorded in the HFEA dataset. As the main analysis was cycle-based and we were unable to link cycles within women undergoing more than one IVF/ICSI cycle, we undertook a sub-group analysis on women undergoing their first treatment cycle.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings should reassure women undergoing blastocyst-stage embryo transfer. For the first time, we have shown that babies born after blastocyst transfer have a similar chance of being healthy as those born after cleavage-stage embryos transfer.

STUDY FUNDING/COMPETING INTEREST(S)

The research activity of Dr Nicola Marconi was funded by the scholarship 'A. Griffini-J. Miglierina', Fondazione Comunitaria del Varesotto, Provincia di Varese, Italy. The authors do not have any competing interests to disclose.

TRIAL REGISTRATION NUMBER

N/A.

Pregnancy Outcomes of Single/Double Blastocysts and Cleavage Embryo Transfers: a Retrospective Cohort Study of 24,422 Frozen-Thawed Cycles

This study aims to evaluate the effect of blastocyst- and cleavage-stage embryo transfers with different numbers of transferred embryos on pregnancy outcomes in China. This was a retrospective cohort study that collected 24,422 frozen-thawed embryo transfer (FET) cycles in two affiliated hospitals of Peking University Health Science Center between January 2015 and May 2018. They were divided into four groups: the single cleavage-stage embryo transfer group (C-1) (763 cycles), double cleavage-stage embryo transfer group (C-2) (13,004 cycles), single blastocyst-stage embryo transfer group (B-1) (7913 cycles), and double blastocyst-stage embryo transfer group (B-2) (2046 cycles). Of the four groups, the live birth rate was the lowest in the C-1 group (11.8%) while it was the highest in the B-2 group (33.6%). However, the B-2 group was accompanied with higher risks of miscarriages, maternal complications, twin births, preterm births, and low birth weight. Compared with the C-2 group, the B-1 group had a lower live birth rate (23.0 vs 29.0%; aOR, 0.78; 95% CI, 0.72-0.85), but also had a lower risk for twin births (1.9 vs 23.4%; aOR, 0.06; 95% CI, 0.04-0.09) and preterm births (9.6 vs 16.1%; aOR, 0.51; 95% CI, 0.41-0.65). The probability of live birth in the B-1 group declined from 0.25 at 20-29 years old to 0.08 at > 40 years old, while the probabilities of adverse outcomes went up with maternal age. It can be concluded that single-blastocyst embryo transfer seems to be the best choice for all maternal ages. This group of embryo transfer has significantly reduced adverse neonatal outcomes. Especially, women with younger maternal age in this group appear to prominently benefit from single-blastocyst transfer.

Effect of embryo stage at transfer on placental histopathology features in singleton live births resulting from fresh embryo transfers

OBJECTIVE

To evaluate the effect of embryo stage at transfer on placental histopathology and perinatal outcome in singleton live births resulting from fresh embryo transfers (ETs).

DESIGN

Retrospective cohort study.

SETTING

Not applicable.

PATIENT(S)

The study population included all live births after fresh ETs during the period from 2009 to 2017.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Primary outcomes included anatomic, inflammatory, vascular malperfusion, and villous maturation placental features. Secondary outcomes included fetal, maternal, and perinatal complications.

RESULT(S)

A total of 677 live births were included in the final analysis and were allocated to the cleavage-stage (n = 252) and blastocyst (n = 425) ET groups. After the adjustment for confounding factors, the blastocyst group was found to be associated with a higher incidence of circummarginate membranes insertion (odds ratio [OR] 1.9, 95% confidence interval [CI] 1.2-3.4), delayed villous maturation (OR 8.5, 95% CI 1.2-69.3), chorangiosis (OR 2.0, 95% CI 1.2-3.8), parenchymal calcifications (OR 10.6, 95% CI 1.4-80.2), and intrapartum nonreassuring fetal heart rate tracing (OR 2.4, 95% CI 1.3-4.5). Compared with cleavage-stage ETs, live births resulting from the blastocysts were associated with a lower incidence of velamentous cord insertion (OR 0.5, 95% CI 0.3-0.9), retroplacental hematoma (OR 0.3, 95% CI 0.1-0.8), subchorionic thrombi (OR 0.3, 95% CI 0.1-0.8), and avascular villi (OR 0.2, 95% CI 0.03-0.7).

CONCLUSION(S)

Live births resulting from fresh cleavage-stage and blastocyst ETs have different placental histopathology features, with a higher rate of intrapartum nonreassuring fetal heart rate tracing in the blastocyst group.

The impact of IVF on birthweight from 1991 to 2015: a cross-sectional study

STUDY QUESTION

Has birthweight (BW) changed over time among IVF-conceived singletons?

SUMMARY ANSWER

Singleton BW has increased markedly over the past 25 years.

WHAT IS KNOWN ALREADY

IVF conceived singletons have had a higher incidence of low BW compared to spontaneously conceived singletons, and this has raised concerns over long-term increased risks of cardio-metabolic disease. However, few causal links between IVF procedures and BW have been robustly established, and few studies have examined whether BW has changed over time as IVF techniques have developed.

STUDY DESIGN, SIZE, DURATION

A total of 2780 live born singletons conceived via IVF or ICSI treated in the reproductive medicine department of a single publicly funded tertiary care centre between 1991 and 2015 were included in this retrospective study. The primary outcome measure was singleton BW adjusted for gestational age, maternal parity and child gender. Multivariable linear regression models were used to estimate the associations between patient prognostic factors and IVF treatment procedures with adjusted BW.

PARTICIPANTS/MATERIALS, SETTING, METHODS

All singletons conceived at the centre following IVF/ICSI using the mother's own oocytes, and non-donated fresh or frozen/thawed embryos with complete electronic data records, were investigated. Available electronic records were retrieved from the Human Fertilization and Embryology Authority for dataset collation. Multiple linear regression analysis was used to evaluate associations between IVF treatment parameters and BW, after adjusting for the year of treatment and patient characteristics and pregnancy factors.

MAIN RESULTS AND THE ROLE OF CHANCE

In the primary multivariable model, singleton BW increased by 7.4 g per year (95% CI: 3.2-11.6 g, P = 0.001), an increase of close to 180 g throughout the 25-year period after accounting for gestational age, maternal parity, child gender, IVF treatment parameters, patient prognostic characteristics and pregnancy factors. Fresh and frozen embryo transfer-conceived singletons showed a similar increase in BW. Frozen/thawed embryo transfer conceived singletons were on average 53 g heavier than their fresh embryo conceived counterparts (95% CI: 3.7-103.3 g, P = 0.035).

LIMITATIONS, REASONS FOR CAUTION

The independent variables included in the study were limited to those that have been consistently recorded and stored electronically over the past two decades.

WIDER IMPLICATIONS OF THE FINDINGS

There has been a progressive BW increase in IVF singletons over time in one large centre with consistent treatment eligibility criteria. Such a change is not seen in the general population of live born singletons in the UK or other developed countries, and seems to be specific to this IVF population. This may be a reflection of changes in practice such as undisturbed extended embryo culture to the blastocyst stage, optimized commercial culture media composition, single embryo transfer and ICSI. Moreover, singletons conceived from frozen/thawed embryos had higher birth weights when compared to their fresh embryo transfer counterparts. The causal pathway is unknown; however, it could be due to the impact on embryos of the freeze/thaw process, self-selection of embryos from couples who produce a surplus of embryos, and/or embryo replacement into a more receptive maternal environment.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the EU FP7 project grant, EpiHealthNet (FP7-PEOPLE-2012-ITN-317146). The authors have no competing interests to declare.

TRIAL REGISTRATION NUMBER

N/A.

The impact of selected embryo culture conditions on ART treatment cycle outcomes: a UK national study

STUDY QUESTION

Are selected embryo culture conditions namely media, oxygen level, and incubator type, associated with IVF live birth rate (LBR) and the health of singleton offspring at birth?

SUMMARY ANSWER

There were statistically significant differences in LBR between the eight culture media systems analysed; however, none of the embryo culture factors showed statistically significant associations with birth weight (BW) in multivariable regression analyses.

WHAT IS KNOWN ALREADY

In clinical ART culture media is the initial environment provided for the growth of human embryos. Pre-implantation development is a critical period of developmental plasticity, which could have long-lasting effects on offspring growth and health. Although some studies have shown an impact of culture medium type on BW, the interaction between culture medium type and associated culture conditions on both treatment success rates (LBR) and offspring BW is largely unexplored. This study aimed to examine these factors in a large multicentre national survey capturing the range of clinical practice.

STUDY DESIGN, SIZE, DURATION

In this cross-sectional study, data from a survey circulated to all UK IVF clinics requesting information regarding culture medium type, incubator type, and oxygen level used in ART between January 2011 and December 2013 were merged with routinely recorded treatment and outcome data held in the Human Fertilisation and Embryology Authority Register up to the end of 2014.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Forty-six (62%) UK clinics responded to the survey. A total of 75 287 fresh IVF/ICSI cycles were captured, including 18 693 singleton live births. IVF success (live birth, singleton or multiple; LB), singleton gestation and singleton gestation-adjusted BW were analysed using logistic and linear regression models adjusting for patient/treatment characteristics and clinic-specific effects.

MAIN RESULTS AND THE ROLE OF CHANCE

Culture medium type was shown to have some impact on LBR (multivariable logistic regression, (MRL); post-regression Wald test, P < 0.001), but not on BW (MLR; post-regression Wald test, P = 0.215). However, blastocyst culture had the largest observed effect on odds of LBR (odds ratio (OR) = 1.35, CI: 1.29–1.42), increased the risk of pre-term birth even when controlling for oxygen tension (MLR; OR = 1.42, CI: 1.23–1.63), and gestation-adjusted BW (MLR, β = 38.97 g, CI: 19.42–58.53 g) when compared to cleavage-stage embryo culture. We noted a very strong effect of clinic site on both LBR and BW, thus confounding between treatment practices and clinic site may have masked the effect of culture conditions.

LIMITATIONS, REASONS FOR CAUTION

Larger datasets with more inter-centre variation are also needed, with key embryo culture variables comprehensively recorded in national treatment registries.

WIDER IMPLICATIONS OF THE FINDINGS

This study is the largest investigation of laboratory environmental effects in IVF on both LBR and singleton BW. Our findings largely agree with the literature, which has failed to show a consistent advantage of one culture media type over another. However, we noted some association of LBR with medium type, and the duration of embryo exposure to laboratory conditions (blastocyst culture) was associated with both LBR and singleton health at birth. Because of the strong effect of clinic site noted, further randomized controlled trials are needed in order to reliably determine the effect of embryo culture on IVF success rates and the growth and health of subsequent offspring.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by the EU FP7 project grant EpiHealthNet (FP7-PEOPLE-2012-ITN -317 146). The authors have no competing interests to declare.

Pregnancy outcomes of fresh IVF conceived pregnancies after embryo transfer at different stages of early embryonic development

Objective: To compare pregnancy outcomes between pregnancies following day 2, day 3, and days 5/6 fresh embryo transfer (ET).Methods: A retrospective cohort study including all pregnancies following fresh IVF/intracytoplasmic sperm injection (ICSI) ET cycles performed between January 2014 and December 2015 at Fertility and In Vitro Fertilization (IVF) Unit of the tertiary Soroka University Medical Center. The study groups consisted of 48, 72, 120, and 144 hours embryos. Pregnancies were confirmed by a serum beta-human chorionic gonadotropin measurement. Data regarding patients' medical history, infertility workup, fertility treatment characteristics, and outcome, as well as obstetrical outcome, were collected from patients' medical records and IVF Laboratory database. Multiple regression models were constructed to control for confounders. Patients who underwent fertility preservation treatment, cycles of oocyte donation or in vitro maturation oocytes, and cases of preimplantation genetic testing were excluded.Results: A total of 534 pregnancies following fresh IVF/ICSI ET on day 2 (n = 189, 35.4%), day 3 (n = 200, 37.5%), and days 5 or 6 (n = 145, 27.2%) were included. Live birth rate demonstrated a linear association to the developmental stage at ET with the highest rates in blastocysts and gradually lower in day 3 and day 2 ET (79.2, 65.8, and 60.6%, respectively, p = .001). A positive linear association was also observed between ET age and clinical pregnancy rate (77.3, 87.5, and 90.3% for days 2, 3, and 5/6, respectively, p = .002), as well as with combined pregnancy complication rate (29, 37.3, and 43.3%, p = .026). However, using multivariate logistic regression model controlling for ET age, maternal age, smoking, obesity, initial HCG level and peak E2 level, live birth rate was comparable between the study groups regardless of ET age. Pregnancy complications were comparable between the groups; however, a composite pregnancy complications variable was higher in the blastocyst pregnancies compared to cleavage embryos pregnancies.Conclusions: The common approach of blastocyst transfer, as high quality of the embryo, has not proven beneficial in terms of live birth rate. Moreover, cleavage stage embryos were not associated with adverse perinatal outcomes. The current data suggest maternal age has an independent effect on live birth.

Preterm Birth in Assisted Reproductive Technology: An Analysis of More Than 20,000 Singleton Newborns

BACKGROUND

Several studies have shown that newborns conceived through the ART procedures were associated with an increased incidence of preterm delivery compared to those conceived spontaneously regardless of the type of ART procedure. The aim of the study was to explore risk factors for preterm birth (PTB) in assisted reproductive technology.

METHOD

In this single center retrospective cohort study, a total of 23,111 singleton newborns from January 2010 to December 2018 were included. The primary outcome in this study was preterm birth, defined as live birth before 37 weeks' gestation.

RESULT

In the 23,111 pregnancies, the incidence of PTB was 7.13%. In multivariate logistic regression analysis model, BMI was an independent predictor for PTB (OR = 1.05, 95% CI: 1.03-1.07; P = 0.00 in IVF/ICSI cycles; OR = 1.08, 95% CI: 1.03-1.12; P = 0.00 in IUI cycles). Also, another independent predictor in ART was male newborns (OR = 1.27, 95% CI: 1.14-1.41; P = 0.00 in IVF/ICSI cycles; OR = 1.60, 95% CI: 1.17-2.18; P = 0.00 in IUI cycles). In IVF/ICSI cycles, PTB was significantly higher in patients with advanced age (9.56% in ≥ 38 years old), and in patients with a history of cesarean section (10.39%). In addition, Blastocyst transfer, and frozen thawed transfer were also risk factor for PTB as compared with cleavage transfer, and fresh transfer, respectively. Moreover, in frozen thawed transfer cycles, stimulated protocol (estrogen-progesterone) increased PTB as compared with natural protocol (OR = 1.33, 95% CI: 1.12-1.59; P = 0.00). This situation was similar in IUI cycles as stimulated protocol also increased PTB when compared with natural protocol (OR = 1.72, 95% CI: 1.19-2.48; P = 0.00).

CONCLUSION

Body mass index (BMI), delivery with male newborn, as well as stimulated protocols, were independent risk factors for PTB in both IVF/ICSI and IUI treatment cycles. In IVF/ICSI cycles, independent risk factors also included maternal, history of cesarean section, frozen thawed transfer, and blastocyst transfer.

Birthweight of singletons born after blastocyst-stage or cleavage-stage transfer: analysis of a data set from three randomized controlled trials

PURPOSE

The present post hoc analysis aims to study the neonatal data of singletons born from three randomized controlled trials (RCTs) which compared the outcome of day 3 and day 5 transfers.

METHODS

Our analysis included 208 liveborn singletons from three existing RCTs (publication dates 2004, 2005, and 2006), 93 children from cleavage-stage transfers and 115 from blastocyst-stage transfers. Vanishing twins were excluded from the analysis. Singleton birthweight was the primary outcome measure. Gestational age and gender of the newborn were accounted for in the multiple regression analysis, along with other confounding factors, such as maternal age, BMI, parity, and smoking behavior.

RESULTS

There was no significant difference in gestational age (median, interquartile range) between cleavage-stage transfer (275 days; 267-281) and blastocyst-stage transfer (277 days; 270-281; p = 0.22). Singleton birthweight (median, interquartile range) was not significantly different between cleavage-stage transfer (3330 g; 3020-3610) and blastocyst-stage transfer (3236 g; 2930-3630; p = 0.40), even following multivariable regression analysis to control for potential maternal and newborn confounders.

CONCLUSION

The gestational age and birthweight were not significantly different after cleavage-stage and blastocyst-stage transfers. One limitation to be recognized is the age of the data, with original data collection dates from 2001 to 2004. Additionally, the RCTs used for the present analysis have a fairly young age restriction.

Obstetric and neonatal outcome of ART in patients with polycystic ovary syndrome: IVM of oocytes versus controlled ovarian stimulation

STUDY QUESTION

Does IVM of immature oocytes retrieved from small antral follicles in women with polycystic ovary syndrome (PCOS) have an impact on obstetric and neonatal outcomes compared to controlled ovarian stimulation (COS)?

SUMMARY ANSWER

Obstetric and neonatal outcomes after IVM appear to be similar to those after COS.

WHAT IS KNOW ALREADY

Women with PCOS have an increased risk of adverse pregnancy outcomes and congenital malformations in their offspring. For patients with PCOS who require IVF, IVM of germinal vesicle (GV)-stage oocytes retrieved from antral follicles has been adopted as a mild approach ART, with improved pregnancy rates over the last two decades. Although reports of obstetrical and neonatal outcomes after IVM have been reassuring, the limited sample sizes in previous studies preclude firm conclusions, and further study is warranted.

STUDY DESIGN, SIZE, DURATION

This is a retrospective observational study analysing obstetric and neonatal data from 1036 clinical pregnancies in unique patients with PCOS who conceived following a cycle of IVM or COS between January 2010 and December 2016 in a tertiary reproductive centre. In total, 393 singleton pregnancies with a gestational age beyond 20 weeks were included. A phenotypic approach was used for the diagnosis of PCOS. Pregnancies following oocyte donation, standard IVF (as opposed to ICSI) or preimplantation genetic testing and pregnancies requiring testicular biopsy in the male partners were excluded.

PARTICIPANTS/MATERIALS,SETTING, METHODS

Pregnancy outcomes were analysed in women with PCOS phenotype A, C or D, as defined by different combinations of the Rotterdam criteria. Data from 164 pregnancies beyond 20 weeks after IVM were compared with those from 229 pregnancies after COS. Pregnancies in the IVM group were obtained after minimal ovarian stimulation and IVF with ICSI of transvaginally collected GV oocytes that had reached the metaphase II stage in vitro after 28 to 40 h of culture. No hCG trigger was administered before oocyte retrieval. Outcome measures were analysed or reported in singleton pregnancies only and included adverse obstetric events and neonatal health parameters, in particular birthweight, prematurity, small-for-gestational age, large-for-gestational age, perinatal death and major/minor malformation rates. The incidence of hypertensive disorders of pregnancy (HDP) and birthweight was analysed by multiple linear and logistic regression, adjusted for relevant treatment variables and maternal characteristics.

MAIN RESULTS AND THE ROLE OF CHANCE

The IVM and the COS groups differed significantly (P < 0.001) for maternal circulating AMH levels and PCOS phenotype distribution, with more of the PCOS phenotype A in the IVM group. Pregnant women in the IVM group were younger than pregnant women in the COS group (P = 0.05). With regard to obstetric complications in singleton pregnancies, in the unadjusted analysis, mothers of infants in the IVM group more often had HDP (29/164 (17.9%) vs 22/229 (9.6%), P = 0.02) compared with mothers in the COS group. Singletons born after IVM and COS had a similar birthweight standard deviation score (SDS) (0.51 ± 0.94 after IVM vs 0.33 ± 1.05 after COS, P = 0.19). Preterm birth rate (32–36.9 weeks) and early preterm birth rate (<32 weeks) were also similar in both groups. The total malformation rate was 4.1% in singletons after IVM and 2.4% in singletons after COS. Multivariate linear regression analysis accounting for relevant confounders demonstrated that parity was the only independent predictive factor (P = 0.04) for birthweight SDS. Multivariate logistic regression analysis showed that BMI, parity and type of ART (IVM as opposed to COS) were significantly correlated with the incidence of HDP. Only patients with the PCOS phenotype A showed a tendency towards a higher risk of HDP in those who underwent IVM compared to those who had COS.

LIMITATIONS, REASONS FOR CAUTION

The study is limited by its retrospective nature and loss to follow-up of a subset of children with no information regarding congenital malformations. Furthermore, the paediatricians who assessed the children after birth were not blinded for the type of ART procedure.

WIDER IMPLICATIONS OF THE FINDINGS

This study provides further evidence that, compared to COS, IVM of oocytes derived from small antral follicles does not adversely affect the neonatal health of the offspring of patients with PCOS. The observed increased risk of HDP in patients with PCOS phenotype A following IVM treatment warrants further scrutiny.

STUDY FUNDING/COMPETING INTEREST(S)

Translational IVM research at Universitair Ziekenhuis Brussel (UZ Brussel) and Vrije Universiteit Brussel (VUB) has been supported by grants from the Institute for the Promotion of Innovation by Science and Technology in Flanders (Agentschap voor Innovatie door Wetenschap en Technologie—IWT, project 110680), the Fund for Research Flanders (Fonds Wetenschappelijk Onderzoek–Vlaanderen—FWO, project G.0343.13) and the Belgian Foundation Against Cancer (HOPE project, Dossier C69). Clinical IVM research was supported by research grants from Cook Medical and Besins Healthcare. M.D.V. reports honoraria for lectures from Cook Medical and Besins Healthcare outside the submitted work. S.S.R. reports honoraria for lectures by MSD and Besins and research grants by MSD, Ferring and Merck Serono outside of the submitted work. C.B. reports personal fees from Merck-Serono, Ferring, IBSA, Finox, MSD and Abbott outside the submitted work. H.T. reports grants from Merck, MSD, Goodlife, Cook, Roche, Besins, Ferring, Mithra (now Allergan) and the Research Fund of Flanders (FWO) and consultancy fees from Finox, Abbott, Obseva and Ovascience outside the submitted work. The other authors have nothing to disclose.

Comparison of perinatal outcomes following blastocyst and cleavage-stage embryo transfer: analysis of 10 years' data from a single centre

RESEARCH QUESTION

Are there greater risks of adverse perinatal outcomes, in particular of congenital malformations, after blastocyst transfer compared with cleavage-stage embryo transfer in IVF?

DESIGN

This was a retrospective cohort analysis from a centre for assisted reproduction at a public hospital in China over the period 2006-2015. The analysis covered all women who conceived (15,254) and newborns (16,213) from IVF/intracytoplasmic sperm injection (ICSI) cycles with cleavage-stage embryo transfer or blastocyst transfer. The principal outcome measures were congenital malformations, preterm birth (PTB), low birthweight (LBW), small for gestational age (SGA) and large for gestational age (LGA).

RESULTS

Logistic regression analysis showed that the sex ratio was imbalanced towards male neonates after blastocyst transfer (P=0.001; adjusted OR 1.17, 95%CI 1.07-1.30) but there were no differences in rates of miscarriage, ectopic pregnancy, stillbirth, very preterm birth (<32 weeks), PTB (<37 weeks), LBW, SGA or LGA between blastocyst transfer and cleavage-stage embryo transfer. A total of 176 congenital malformations (123 cleavage-stage embryos versus 53 blastocysts) were identified both in newborns and aborted fetuses, but the difference between groups was not statistically significant.

CONCLUSIONS

There was no difference in the risks of adverse perinatal outcomes, and in particular of congenital malformation, after blastocyst transfer compared with cleavage-stage transfer, although there was a sex ratio imbalance towards male neonates after blastocyst transfer.

Birthweight of singletons born after cleavage-stage or blastocyst transfer in fresh and warming cycles

STUDY QUESTION

Does extended culture to the blastocyst stage affect singleton birthweight after either fresh or vitrified-warmed embryo transfer?

SUMMARY ANSWER

Singleton birthweight z-scores did not vary significantly after a fresh blastocyst transfer, whereas the additional effect of vitrification remains inconclusive.

WHAT IS KNOWN ALREADY

Observational studies have associated extended culture with an increased risk of preterm birth and low birthweight. On the contrary, in terms of birthweight and gestational age, singletons born after vitrification have been associated with a better perinatal outcome when compared to those born following a fresh transfer.

STUDY DESIGN, SIZE, DURATION

Our post-hoc cohort analysis on neonatal outcomes included 447 liveborn singletons was derived from a recent retrospective analysis on cumulative live birth rates after cleavage-stage and blastocyst transfers. These babies were born following a fresh single cleavage-stage transfer (FCT Day 3, n = 113), fresh single blastocyst transfer (FBT Day 5, n = 218), vitrified-warmed cleavage-stage transfer (VCT Day 3, n = 58) or vitrified-warmed blastocyst transfer (VBT Day 5, n = 58).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Singleton birthweight was the primary outcome measure. Gestational age and gender of the newborn were accounted for by using birthweight z-scores in a multivariable linear regression analysis, adjusting for other confounders (maternal age, BMI, parity and smoking behaviour). Vanishing twins were excluded from the analysis.

MAIN RESULTS AND THE ROLE OF CHANCE

A significantly lower z-score was observed after blastocyst transfer compared to cleavage-stage transfer in the vitrified-warmed Day 5 group (P = 0.013), a difference not observed in the fresh transfer groups (P = 0.32). Following multivariable regression analysis [adjusted regression coefficient (95% confidence interval)], the FCT and FBT groups showed no significant influence on the birthweight z-scores after fresh transfer [-0.19 (-0.44; 0.05)], but the transfer of vitrified blastocysts (VBT) was associated with a lower birthweight [-0.52 (-0.90; -0.15)] compared with the transfer of vitrified cleavage-stage embryos (VCT).

LIMITATIONS, REASONS FOR CAUTION

The present cohort was relatively small, especially in the vitrified-warmed subgroups. Pregnancy-associated factors possibly influencing birthweight (such as diabetes, hypertension, pre-eclampsia) were also not accounted for in the analysis.

WIDER IMPLICATIONS OF THE FINDINGS

Different ART procedures, including extended culture and vitrification, may hold potential safety issues. These results require further confirmation in future larger studies.

STUDY FUNDING/COMPETING INTEREST(S)

None.

TRIAL REGISTRATION NUMBER

N/A.

Live birth rate and neonatal outcome following cleavage-stage embryo transfer versus blastocyst transfer using the freeze-all strategy

RESEARCH QUESTION

What are the live birth rates and neonatal outcomes following cleavage-stage embryo transfer and blastocyst transfer in a freeze-all treatment scenario?

DESIGN

This was a retrospective cohort study. All good-quality embryos were frozen on the third day; the remaining embryos were grown on until they reached blastocyst stage and then frozen. Between 2007 and 2016, 11,801 patients underwent cleavage-stage embryo transfer and 1009 patients underwent blastocyst transfer in the first treatment cycle using the freeze-all strategy. The live birth rate and neonatal outcomes were evaluated.

RESULTS

The live birth rate in the first frozen embryo transfer cycle was higher following blastocyst transfer than following cleavage-stage transfer (69.1% versus 55.5%, P < 0.01), but there was no difference in live birth rate in the second frozen embryo transfer cycle between blastocyst transfer and cleavage-stage transfer (45.2% versus 52.7%, P > 0.05). Similarly, no difference was found in the cumulative live birth rate for the first complete IVF cycle (71.1% versus 69.2%, P > 0.05). Blastocyst transfer gave a higher risk of preterm singleton delivery than did cleavage-stage transfer. However, there was no difference in the risk of early preterm delivery, low birth weight, very low birth weight, high birth weight and very high birth weight between the two groups.

CONCLUSIONS

There is no evidence to support the superiority of blastocyst transfer compared with cleavage-stage transfer in a freeze-all treatment scenario. There may be a higher risk of preterm singleton delivery following blastocyst transfer than following cleavage-stage transfer but further studies are needed to verify this.

The risk of birth defects among children born after vitrified blastocyst transfers and those born after fresh and vitrified cleavage-stage embryo transfers

PURPOSE

To explore the risk of birth defects among children born after vitrified blastocyst transfers and those born after fresh and vitrified cleavage-stage embryo transfers.

METHODS

A retrospective cohort study was conducted including infants born after fresh and vitrified day 3 embryo transfers and those born after vitrified day 5 or 6 blastocyst transfers from January 2005 through December 2016. The outcome measures included any birth defect, multiple birth defects and 13 individual categories of birth defects.

RESULTS

Any birth defect occurred in 1.15% of infants born after fresh day 3 embryo transfers, 1.75% of infants born after vitrified day 3 embryo transfers, 1.60% of infants born after vitrified day 5 blastocyst transfers and 1.10% of infants born after vitrified day 6 blastocyst transfers. There was no difference in the risk of birth defects between vitrified blastocyst-stage transfers and vitrified cleavage-stage transfers (including day 5 vs. day 3 and day 6 vs. day 3) among all births or in only singletons or twins. For infants born after cleavage-stage embryo transfers at day 3, there was no difference in the risk of birth defects between fresh embryo transfers and vitrified embryo transfers among all births or in only singletons or twins.

CONCLUSIONS

Transfer of vitrified day 5 or 6 blastocysts does not increase the risk of birth defects compared with vitrified day 3 embryos. However, randomized control trials and follow-up studies of the long-term outcome of children born after blastocyst-stage transfers are needed to confirm the clinical safety of extending embryo culture to the blastocyst stage.

Birthweight in infants conceived through in vitro fertilization following blastocyst or cleavage-stage embryo transfer: a national registry study

PURPOSE

In vitro fertilization (IVF) infants have lower birthweights than their peers, predisposing them to long-term health consequences. Blastocyst transfer (BT), at day 5-6 post-fertilization, is increasing in usage, partially due to improved pregnancy outcomes over cleavage-stage transfer (CT, day 2-3). Data to date, however, have been inconclusive regarding BT's effects on birthweight.

METHODS

Participants included all US autologous, single-gestation, fresh embryo transfer cycles initiated from 2007 to 2014 that resulted in a term infant (N = 124,154) from the National Assisted Reproductive Technology Surveillance System. Generalized linear models including obstetric history, maternal demographics, and infant sex and gestational age were used to compare birthweight outcomes for infants born following BT (N = 67,169) with infants born following CT (N = 56,985) and to test for an interaction between transfer stage and single embryo transfer (SET).

RESULTS

Infants born following BT were 6 g larger than those born following CT (p = 0.04), but rates of macrosomia (RR 1.00, 95% CI 0.96-1.04) and low birthweight (LBW, RR 1.00, 95% CI 0.93-1.06) were not different between the groups. The interaction between SET and transfer stage was significant (p = 0.02). Among SET infants, BT was associated with 19.26 g increased birthweight compared to CT (p = 0.008).

CONCLUSIONS

The increase in birthweights identified following BT is unlikely to be clinically relevant, as there were no differences in rates of macrosomia or LBW. These findings are clinically reassuring and indicate that the increasing use of BT is unlikely to further decrease the on average lower birthweights seen in IVF infants compared to their naturally conceived peers.

Assisted reproductive technologies: a hierarchy of risks for conception, pregnancy outcomes and treatment decisions

The use of assisted reproductive technologies (ART) for the treatment of infertility has grown exponentially over the last 20 years, and now accounts for 4% of all births in Australia, and over 1 m births annually around the globe. There is consistent reporting of increased risk of adverse perinatal outcomes and birth defects following infertility treatment. However, change in practice has been stymied by critical knowledge gaps with regards to (a) the relative contribution of patient and treatment factors to adverse outcomes, (b) the independent contribution of specific contemporary treatments and treatment combinations to outcomes, (c) the impact of innovations in laboratory and clinical practice on treatment success and observed risk and (d) changes over time in patient characteristics. Here we summarize key findings from the South Australian Birth Cohort, which is a whole-of-population cohort of over 300,000 births from 1986 to 2002. Relative to spontaneous conceptions, singletons from assisted conception were more likely to be stillborn [odds ratio (OR)=1.82; 95% confidence interval (CI) 1.34-2.48], while survivors as a group were comprehensively disadvantaged at birth, including lower birth weight (OR=2109 g; 95% CI 2129-289), very low birth weight (OR=2.74; 95% CI 2.19-3.43), very preterm birth (OR=2.30; 95% CI 1.82-2.90) and neonatal death (OR=2.04; 95% CI 1.27-3.26). Major birth defects, including cardiac, urogenital and musculoskeletal defects are doubled after fresh ICSI cycles, which is a particular concern as ICSI now accounts for 70% of all treatment cycles globally. Future study is needed to provide contemporary, precise evidence to inform patient and clinic decision making, and generate knowledge for future innovation in ART laboratory methods and clinical practice, thereby optimizing treatment and health outcomes while reducing adverse events.

Influence of cryopreservation on perinatal outcome after blastocyst- vs cleavage-stage embryo transfer: systematic review and meta-analysis

OBJECTIVE

To compare the perinatal outcomes of singleton pregnancies resulting from blastocyst- vs cleavage-stage embryo transfer and to assess whether they differ between fresh and frozen embryo transfer cycles.

METHODS

A systematic review of the literature was carried out using the Scopus, MEDLINE and ISI Web of Science databases with no time restriction. We included only peer-reviewed articles involving humans, in which perinatal outcomes of singleton pregnancies after blastocyst-stage embryo transfer were compared with those after cleavage-stage embryo transfer. Primary outcomes were preterm birth before 37 weeks and low birth weight (< 2500 g). Secondary outcomes were very preterm birth before 32 weeks, very low birth weight (< 1500 g), small-for-gestational-age (SGA), large-for-gestational-age (LGA), perinatal mortality and congenital anomaly. A meta-analysis was performed using a random-effects model. Three subgroups were evaluated: fresh only, frozen only and fresh plus frozen embryo transfer cycles.

RESULTS

From a total of 3928 articles identified, 14 were selected for qualitative/quantitative analysis. Significantly higher incidences of preterm birth < 37 weeks (11 studies, n = 106 629 participants; risk ratio (RR), 1.15 (95% CI, 1.05 - 1.25); P = 0.002) and very preterm birth < 32 weeks (seven studies, n = 103 742; RR, 1.16 (95% CI, 1.02-1.31); P = 0.03) were observed after blastocyst- than after cleavage-stage embryo transfer in fresh cycles. However, the risk of preterm and very preterm birth was similar after blastocyst- and cleavage-stage transfers in frozen and fresh plus frozen cycles. Overall effect size analysis revealed fewer SGA deliveries after blastocyst- compared with cleavage-stage transfer in fresh cycles but a similar number in frozen cycles. Conversely, more LGA deliveries were observed after blastocyst- compared with cleavage-stage transfer in frozen cycles (two studies, n = 39 044; RR, 1.18 (95% CI, 1.09-1.27); P < 0.0001) and no differences between the two groups in fresh cycles (four studies, n = 42 982; RR, 1.14 (95% CI, 0.97-1.35); P = 0.11). There were no differences with respect to low birth weight, very low birth weight or congenital anomalies between blastocyst- and cleavage-stage transfers irrespective of the cryopreservation method employed. Only one study reported a higher incidence of perinatal mortality after blastocyst- vs cleavage-stage embryo transfer in frozen cycles, while no differences were found in fresh cycles.

CONCLUSIONS

Our results suggest that cryopreservation of embryos can influence outcome of pregnancy conceived following blastocyst- vs cleavage-stage embryo transfer in terms of preterm birth, very preterm birth, LGA, SGA and perinatal mortality. Caution should be exercised in interpreting these findings given the low level of evidence and wide heterogeneity of the studies. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Blastocyst transfer is not associated with increased unfavorable obstetric and perinatal outcomes compared with cleavage-stage embryo transfer

BACKGROUND

Recent studies demonstrated controversial results of whether there are risks in fetal outcomes after blastocyst-stage embryos transfer (BT) compared with cleavage-stage embryos transfer (CT).

AIMS

To compare the implantation rates (IR), clinical pregnancy rates (cPR), birth rates (BR), gestational weeks, preterm birth rates, birth weights and low birth weight rates between CT and BT groups.

METHODS

A retrospective study of 1627 embryos transfer cycles was performed from May 2014 to April 2015. The cycles were divided into two groups according to transfer stage: CT on Day 3 (n = 798) and BT on Day 5 (n = 829). For the CT group, it must have surplus embryos and only surplus embryos developed to available blastocysts, the cleavage-stage embryos could be included. The clinical outcomes of two groups were analyzed.

RESULTS

The IR in CT group was lower than BT group (48.98% vs. 60.68%; p < 0.01). There were no significant differences in the clinical pregnancy rate and birth rate between BT and CT groups. For singletons and twin deliveries, there were no significant differences in gestational weeks, preterm birth rates, birth weights and low birth weight rates between two groups.

CONCLUSION

Blastocysts had higher implantation potential than cleavage-stage embryos. Extended embryo culture was not related to increased adverse obstetric and perinatal outcome.

Comparative neonatal outcomes in singleton births from blastocyst transfers or cleavage-stage embryo transfers: a systematic review and meta-analysis

BACKGROUND

Comparative neonatal outcomes with respect to singleton births from blastocyst transfers or cleavage-state embryo transfers are controversial with respect to which method is superior. Many studies have yielded contradictory results. We performed a systematic review and meta-analysis for the purpose of comparing neonatal outcomes in single births following IVF/ICSI.

METHODS

We searched the Medline, Embase and Cochrane Central Register of Clinical Trials (CCTR) databases until October 2016. Studies and trials that contained neonatal outcomes for singleton births were included. Data were extracted in 2 × 2 tables. The analysis was performed using Rev Man 5.1 software. Risk ratios (RRs) and risk differences, with 95% confidence intervals, were calculated to assess the results of each outcome. Subgroups were applied in all outcomes. Newcastle-Ottawa scale (NOS) checklists were used to assess the quality of the referenced studies.

RESULTS

Twelve studies met the criteria in this meta-analysis. There was a high risk of preterm birth after blastocyst embryo transfer versus the risk after cleavage-stage transfer (RR: 1.11, 95% CI: 1.01-1.22). For the "only fresh" subgroup, the outcome was coincident (RR: 1.16, 95% CI: 1.06-1.27). For the "fresh and frozen" and "only frozen" subgroups, there were no differences. Patients who received fresh blastocyst embryo transfers had a high risk of very preterm births (RR: 1.16, 95% CI: 1.02-1.31). Finally, cleavage-stage embryo transfers were associated with a high risk of infants who were small for gestational age (0.83, 95% CI: 0.76-0.92) and a low risk of those who were large for gestation age (1.14, 95% CI: 1.04-1.25).

CONCLUSIONS

The risks of preterm and very preterm births increased after fresh blastocyst transfers versus the risks after fresh cleavage-stage embryo transfers. However, in frozen embryo transfers, there were no differences. Blastocyst embryo transfers resulted in high risks of infants who were large for gestational age, and cleavage-stage embryo transfers resulted in high risks of infants who were small for gestational age.

Systematic review of worldwide trends in assisted reproductive technology 2004-2013

BACKGROUND

Assisted Reproductive Technology (ART) has undergone considerable changes over the last decade, with consequences on ART outcomes in different regions of the world being unknown.

METHODS

We conducted a systematic review of published national and regional ART registry data to assess how changes in clinical practice between 2004 and 2013 have impacted outcomes in Australia and New Zealand, Canada, Continental Europe, the United Kingdom (U.K.), Japan, Latin America, and the United States (U.S.). The data reflect 7,079,145 total ART cycles utilizing both fresh and previously cryopreserved embryos from autologous oocytes that resulted in 1,454,724 live births. This review focused on the following measures: ART cycle volume, use of cryopreserved embryos, single embryo transfer (SET), live birth rates in fresh and frozen-thawed cycles, and perinatal outcomes in recent years.

RESULTS

SETs and utilization of frozen-thawed embryos increased worldwide over the study period. In 2012 SET utilization in all ART cycles was highest in Japan and Australia/New Zealand (82.6% and 76.3% respectively) and lowest in Latin America (16.0%). While gradual improvements in live birth rates were observed in most regions, some demonstrated declines. By 2012-2013, fresh cycle live birth rates were highest in the U.S. (29%) and lowest in Japan (5%). In Japan, the observed decline in fresh cycle live birth rate coincided with transition to minimal stimulation protocols, transfer of frozen-thawed rather than fresh embryos, and implementation of an SET policy. Similarly, implementation of an SET policy in parts of Canada was followed by a decline in fresh cycle live birth rate. Increasing live birth rates in frozen-thawed embryo cycles, seen all over the world, partially compensated for declines in fresh ART cycles. During 2012-2013 Australia/New Zealand and Japan reported the lowest multiple delivery rates of 5.6 and 4% respectively while the US had the highest of 27%. In recent years, preterm delivery rates in all regions ranged between 9.0 to 16.6% for singletons, 53.9 to 67.3% for twins, and 91.4 to 100% for triplets and higher order multiples. Inconsistencies in the way perinatal outcome data are presented by various registries, made comparison between regions difficult.

CONCLUSIONS

ART practices are characterized by outcome differences between regions. International consensus on the definition of ART success, which accounts for perinatal outcomes, may help to standardize worldwide ART practice and improve outcomes.

TRIAL REGISTRATION

PROSPERO ( CRD42016033011 ).

Risk of adverse pregnancy and perinatal outcomes after high technology infertility treatment: a comprehensive systematic review

In the literature, there is growing evidence that subfertile patients who conceived after infertility treatments have an increased risk of pregnancy and perinatal complications and this is particularly true for patients who conceived through use of high technology infertility treatments. Moreover, high technology infertility treatments include many concomitant clinical and biological risk factors. This review aims to summarize in a systematic fashion the current evidence regarding the relative effect of the different procedures for high technology infertility treatments on the risk of adverse pregnancy and perinatal outcome. A literature search up to August 2016 was performed in IBSS, SocINDEX, Institute for Scientific Information, PubMed, Web of Science and Google Scholar and an evidence-based hierarchy was used to determine which articles to include and analyze. Data on prepregnancy maternal factors, low technology interventions, specific procedures for male factor, ovarian tissue/ovary and uterus transplantation, and chromosomal abnormalities and malformations of the offspring were excluded. The available evidences were analyzed assessing the level and the quality of evidence according to the Oxford Centre for Evidence-Based Medicine guidelines and the Grading of Recommendations Assessment, Development, and Evaluation system, respectively. Current review highlights that every single procedure of high technology infertility treatments can play a crucial role in increasing the risk of pregnancy and perinatal complications. Due to the suboptimal level and quality of the current evidence, further well-designed studies are needed.

Obstetrical and perinatal outcomes following blastocyst transfer compared to cleavage transfer: a systematic review and meta-analysis

STUDY QUESTION

Is blastocyst transfer safe when compared to cleavage stage embryo transfer regarding obstetric and perinatal outcomes?

SUMMARY ANSWER

The clinical equipoise between blastocyst and cleavage stage embryo transfer remains as the evidence associating blastocyst transfer with some adverse perinatal outcomes is of low/very low quality.

WHAT IS KNOWN ALREADY

Extended embryo culture to the blastocyst stage provides some theoretical advantages and disadvantages. While it permits embryo self-selection, it also exposes those embryos to possible harm due to the in vitro environment. Both effectiveness and safety should be weighed to permit evidence-based decisions in clinical practice.

STUDY DESIGN, SIZE, DURATION

This is a systematic review and meta-analysis of randomized controlled trials (RCTs) and observational studies reporting perinatal outcomes for singletons comparing the deliveries resulting from blastocyst and cleavage stage embryo transfer. Observational studies were included because the primary outcomes, perinatal mortality and birth defects, are rare and require a large number of participants (>50 000) to be properly assessed. The last electronic searches were last run on 11 March 2016.

PARTICIPANTS/MATERIALS, SETTING, METHOD

There were 12 observational studies encompassing 195 325 singleton pregnancies included in the study. No RCT reported the studied outcomes. The quality of the included studies was evaluated according to the Newcastle-Ottawa Scale and the quality of the evidence was evaluated according to GRADE criteria.

MAIN RESULTS AND THE ROLE OF CHANCE

Blastocyst stage transfer was associated with increased risks of preterm birth (<37 weeks), very preterm birth (<32 weeks), large for gestational age and perinatal mortality, although the latter was only identified from one study. Conversely, blastocyst stage transfer was associated with a decrease in the risks of small for gestational age and vanishing twins, although the latter was reported by only one study.

LIMITATIONS, REASONS FOR CAUTION

The observational nature of the included studies and some inconsistency and imprecision in the analysis contributed to decreasing our confidence in the estimates.

WIDER IMPLICATIONS OF THE FINDINGS

Due to the overall low quality of available evidence, the clinical equipoise between cleavage stage and blastocyst transfer remains. More large well-conducted studies are needed to clarify the potential risks and benefits of blastocyst transfer. As this review was initiated to support global recommendations on best practice, and in light of the challenges in lower resource settings to offer extended culture to blastocyst stage, it is critical to take into consideration these obstetric and neonatal outcomes in order to ensure any recommendation will not result in the overburdening of existing maternal and child health care systems and services.

STUDY FUNDING/COMPETING INTERESTS

No external funding was either sought or obtained for this study. The authors have no competing interests to declare.

PROSPERO REGISTRATION NUMBER

CRD42015023910.

Population trends and live birth rates associated with common ART treatment strategies

STUDY QUESTION

Have ART live birth rates improved in Australia over the last 12 years?

SUMMARY ANSWER

There were striking improvements in per-cycle live birth rates observed for frozen/thaw embryo transfers, blastocyst transfer and single embryo transfer (SET), while live birth rates following ICSI were lower than IVF for non-male factor infertility in most years.

WHAT IS ALREADY KNOWN

ART and associated techniques have become the predominant treatment of infertility over the past 30 years in most developed countries. However, there are differences in ART laboratory and clinical practices, and success rates worldwide. Australia has one of the highest ART utilization rates and lowest multiple birth rates in the world, thus providing a unique setting to investigate the contribution of common ART strategies in an unrestricted population of patients to ART success rates.

STUDY DESIGN, SIZE, DURATION

A retrospective cohort study of 585 065 ART treatment cycles performed in Australia between 2002 and 2013 using the Australian and New Zealand Assisted Reproduction Database (ANZARD).

PARTICIPANTS MATERIALS, SETTING, METHOD

An unrestricted population of all women who underwent autologous ART treatment between 2002 and 2013. Visual descriptive analysis was used to assess the trends in ART procedures by the calendar years. Adjusted odds ratios (aORs) of a live birth for four common ART techniques were calculated after controlling for important confounders including female age, infertility diagnosis, stage of the embryo (blastocyst versus cleavage stage), type of embryo (fresh versus thawed), fertilization method (IVF versus ICSI) and number of embryos transferred (SET versus multiple embryos).

MAIN RESULTS AND THE ROLE OF CHANCE

The overall live birth rate per embryo transfer increased from 19.2% in 2002 to 23.3% in 2013 (21.9-24.3% for fresh embryo transfers and 14.6-23.3% for frozen/thaw embryo transfers). This occurred concurrently with an increase in SET from 29.7% to 78.9%, and an increase in the average age of women undergoing treatment from 35.0 to 35.9 years. Individuals who had a frozen/thaw embryo transfer cycle in 2002 had 43% (aOR: 0.57, 95% CI: 0.53-0.61) reduced odds of a live birth compared with a fresh embryo transfer cycle. This contrasted with 16% (aOR: 0.84, 95% CI: 0.80-0.98) reduced odds of a live birth from frozen/thaw embryo transfer cycles in 2013. In 2013, the odds of blastocyst transfer resulting in a live birth were more than twice as great as for cleavage stage transfer (aOR 2.01, 95% CI: 1.92-2.11). The adjusted odds of live birth per SET compared with multiple embryo transfer increased significantly over the last 12 years, from a 38% reduced odds of a live birth follow SET in 2002 (aOR: 062, 95% CI: 0.57-0.67) compared to an 8% reduced odds in 2013 (aOR: 0.92, 95% CI: 0.87-0.98). The aOR of a live birth using ICSI compared to IVF in non-male factor patients was lower in most years bringing into question its widespread use.

LIMITATION, REASONS FOR CAUTION

This is a retrospective cohort analysis and cannot confirm causality. High-level evidence on the effectiveness of particular ART techniques, particularly ICSI and blastocyst culture, requires prospective randomized controlled trials or detailed statistical analysis using large-scale data that counts for fertilization failure, embryo loss, prognostic factors and cycle characteristics.

WIDER IMPLICATION OF THE FINDINGS

The most striking improvements in ART success rates in Australia have been observed for frozen/thaw embryo transfers, blastocyst transfer and SET. Further studies of the role of ICSI in non-male factor infertility and blastocyst transfer success rates that take into account embryo loss are needed.

STUDY FUNDING/COMPETING INTERESTS

No funding was received to undertake this study. The authors declare that they do not have competing interests with this study.

TRIAL REGISTRATION NUMBER

NA.

From Embryos to Adults: A DOHaD Perspective on In Vitro Fertilization and Other Assisted Reproductive Technologies

Human in vitro fertilization (IVF) as a treatment for infertility is regarded as one of the most outstanding accomplishments of the 20th century, and its use has grown dramatically since the late 1970s. Although IVF is considered safe and the majority of children appear healthy, reproductive technologies have been viewed with some skepticism since the in vitro environment deviates substantially from that in vivo. This is increasingly significant because the Developmental Origins of Health and Disease (DOHaD) hypothesis has illuminated the sensitivity of an organism to its environment at critical stages during development, including how suboptimal exposures restricted specifically to gamete maturation or the preimplantation period can affect postnatal growth, glucose metabolism, fat deposition, and vascular function. Today, some of the physiological metabolic phenotypes present in animal models of IVF have begun to emerge in human IVF children, but it remains unclear whether or not in vitro embryo manipulation will have lasting health consequences in the offspring. Our expanding knowledge of the DOHaD field is fueling a paradigm shift in how disease susceptibility is viewed across the life course, with particular emphasis on the importance of collecting detailed exposure information, identifying biomarkers of health, and performing longitudinal studies for any medical treatment occurring during a developmentally vulnerable period. As IVF use continues to rise, it will be highly valuable to incorporate DOHaD concepts into the clinical arena and future approaches to public health policy.

Neonatal and maternal outcome after blastocyst transfer: a population-based registry study

BACKGROUND

Previous studies have shown a higher risk of birth defects and preterm birth (PTB) in singletons born after blastocyst transfer as compared to singletons born after cleavage-stage transfer. Few studies have investigated the maternal outcomes.

OBJECTIVE

We sought to analyze the neonatal and maternal outcome after blastocyst transfer (day 5-6) compared to transfer of cleavage-stage embryos (day 2-3) and spontaneous conception.

STUDY DESIGN

This was a population-based retrospective registry study including all singleton deliveries after blastocyst transfer in Sweden from 2002 through 2013. The in vitro fertilization register was cross-linked with the Swedish Medical Birth Register, the Register of Birth Defects, and the National Patient Register. Deliveries after blastocyst transfer were compared with deliveries after cleavage-stage transfer and deliveries after spontaneous conception. Outcome measures included birth defects, PTB, low birthweight, small for gestational age, large for gestational age, perinatal mortality, placenta previa, placental abruption, and preeclampsia. Crude and adjusted odds ratios (AOR) with 95% confidence interval (CI) were calculated. Adjustment was made for year of birth of child, maternal age, parity, smoking, body mass index, years of involuntary childlessness, and child's sex and, for cleavage stage, also for number of oocytes retrieved, number of embryos transferred, and fresh/frozen embryo transfer.

RESULTS

There were 4819 singletons born after blastocyst transfer, 25,747 after cleavage-stage transfer, and 1,196,394 after spontaneous conception. Singletons born after blastocyst transfer had no increased risk of birth defects compared to singletons born after cleavage-stage transfer (AOR, 0.94; 95% CI, 0.79-1.13) or spontaneous conception (AOR, 1.09; 95% CI, 0.92-1.28). Perinatal mortality was higher in the blastocyst vs the cleavage-stage group (AOR, 1.61; 95% CI, 1.14-2.29). When comparing singletons born after blastocyst transfer to singletons born after spontaneous conception, a higher risk of PTB (<37 weeks) was seen (AOR, 1.17; 95% CI, 1.05-1.31). Singletons born after blastocyst transfer had a lower rate of low birthweight (AOR, 0.83; 95% CI, 0.71-0.97) as compared to cleavage-stage transfer. The rate of being small for gestational age was lower in singletons born after blastocyst transfer as compared to both cleavage-stage and spontaneous conception (AOR, 0.71; 95% CI, 0.56-0.88 and AOR, 0.70; 95% CI, 0.57-0.87, respectively). The risk of placenta previa and placental abruption was higher in pregnancies after blastocyst transfer as compared to pregnancies after cleavage-stage (AOR, 2.08; 95% CI, 1.70-2.55 and AOR, 1.62; 95% CI, 1.15-2.29, respectively) and spontaneous conception (AOR, 6.38; 95% CI, 5.31-7.66 and AOR, 2.31; 95% CI, 1.70-3.13, respectively).

CONCLUSION

No increased risk of birth defects was found in singletons born after blastocyst transfer. Perinatal mortality and risk of placental complications were higher in the blastocyst group as compared to the cleavage-stage group, observations that need further investigations.

The impact of physiological oxygen during culture, and vitrification for cryopreservation, on the outcome of extended culture in human IVF

Extended culture has facilitated the move to single blastocyst transfer, resulting in significant increases in implantation and live birth rate, while concomitantly reducing fetal loss during pregnancy. However, concerns have been raised regarding subsequent neo-natal outcomes following extended culture. Analysis of the literature reveals differences in outcomes according to geographical region and between individual clinics. A common factor amongst reports of potentially adverse outcomes following blastocyst transfer appears to be that atmospheric (~20%) oxygen was typically employed for embryo culture. Clinics and countries utilizing physiological concentrations of oxygen (~5%) have not reported adverse perinatal outcomes with blastocyst transfer. Atmospheric oxygen imposes significant negative effects upon the embryo's molecular and cellular physiology, and further it increases the sensitivity of the preimplantation embryo to other stressors in the laboratory. With the recent adoption of vitrification for blastocyst cryopreservation, cumulative pregnancy rates per cycle with extended culture will increase significantly. Consequently, rather than perceiving extended culture as a potentially negative procedure, it is concluded that neo-natal data need to be interpreted in light of the conditions used to culture and cryopreserve blastocysts, and that furthermore a policy of embryo culture using 20% oxygen can no longer be justified.