Perinatal Risks Associated with Early Vanishing Twin Syndrome following Transfer of Cleavage- or Blastocyst-Stage Embryos

Vanishing twin syndrome is associated with first-trimester intrauterine hematoma in twin pregnancies after in vitro fertilization

RESEARCH QUESTION

Is there an association between intrauterine hematoma (IUH), vanishing twin syndrome (VTS), and subsequent complications in twin pregnancies after in vitro fertilization (IVF)? What are the risk factors for these complications?

DESIGN

Women who presented with two live gestational sacs following double embryo transfer were included. Patients with systematic diseases, artificial fetal reduction, and incomplete data were excluded. Further stratification of IUH pregnancies was performed according to IUH-related characteristics (i.e., volume, changing pattern, and relationship with fetal cardiac activities). The primary outcome was the incidence of VTS, while adverse outcomes in the surviving singleton and the gestational age of VTS were secondary outcomes.

RESULTS

The incidence of IUH was 13.8%. A total of 1,078 twin pregnancies including 539 IUH pregnancies and 539 non-IUH pregnancies were included. IUH pregnancy was associated with higher risks of VTS (26.9% vs. 18.7%, p = 0.001) as well as a higher incidence of preterm birth (p = 0.001, crude OR = 1.98, 95% CI 1.28-3.09, adjusted OR = 1.19, 95% CI 1.09-1.24), threatened abortion (p < 0.001, crude OR = 9.12, 95% CI 2.90-28.69, adjusted OR = 6.63, 95% CI 1.69-14.67), and postpartum hemorrhage (p = 0.024, crude OR = 3.13, 95% CI 1.09-8.99, adjusted OR = 1.16, 95% CI 1.08-1.32) in the surviving singleton. There was no significant difference in risks of other complications. The absence of fetal cardiac activities at the diagnosis of IUH predicted VTS (p < 0.001, crude OR 4.67, 95% CI 3.67-5.78, adjusted OR 3.33, 95% CI 1.56-5.14) and fetal loss at smaller gestational age (7.81 ± 2.10 vs. 11.39 ± 5.60 weeks, p < 0.001), while an IUH with an increasing volume did not increase the risk of VTS but might induce threatened abortion in the surviving fetus (p < 0.001, crude OR 1.84, 95% CI 1.32-2.55, adjusted OR 1.72, 95% CI 1.13-2.13).

CONCLUSIONS

IUH was a risk factor for VTS in twin pregnancies following double embryo transfer and elevated the risks of threatened abortion, preterm birth, and postpartum hemorrhage in the surviving singleton. The absence of fetal cardiac activities at the diagnosis of IUH elevated the risks of VTS, while an IUH with an increasing volume was associated with threatened abortion without elevating the risks of VTS. An IUH diagnosed before the presence of fetal cardiac activities also resulted in an earlier miscarriage. The study suggests that attention be paid to twin pregnancies with first-trimester IUH to prevent VTS and subsequent adverse perinatal outcomes.

HIGHLIGHTS

First-trimester intrauterine hematoma (IUH) following double embryo transfer is associated with a higher incidence of vanishing twin syndrome (VTS) and elevated subsequent risk of threatened abortion, preterm birth, and postpartum hemorrhage in the surviving singleton. Other perinatal outcomes were not associated with the diagnosis of first-trimester IUH. The absence of fetal cardiac activities at the diagnosis of IUH was of predictive value toward VTS, while an IUH with an increasing size was associated with threatened abortion without elevating the risk of VTS. Incomplete fetal cardiac activities and earlier detection of an IUH might also predict miscarriage at smaller gestational age.

The late vanishing of a co-twin contributes to adverse perinatal outcomes in the surviving singleton

STUDY QUESTION

Is the vanishing of a co-twin after or before the ultrasonic registration of cardiac activity at approximately 6-8 weeks of gestation associated with adverse perinatal outcomes?

SUMMARY ANSWER

The timing of the demise of a co-twin after the registration of cardiac activity is an independent risk factor for adverse perinatal outcomes.

WHAT IS KNOWN ALREADY

A significant body of evidence has confirmed that vanishing twin (VT) pregnancies are associated with higher levels of risk for preterm birth (PTB), low birthweight (LBW), small-for-gestational age (SGA) and perinatal mortality, compared with singleton pregnancy. However, the impact of co-twin vanishing, before or after the presence, of cardiac activity, on perinatal outcomes has yet to be extensively investigated.

STUDY DESIGN, SIZE, DURATION

We retrospectively reviewed the medical records of 38 876 singletons delivered from ART cycles between 2006 and 2018, at the Peking University Third Hospital.

PARTICIPANTS/MATERIALS, SETTING, METHODS

In total, 35 188 singletons were delivered from the singleton pregnancy group, 2256 singletons from the VT pregnancy group after that cardiac activity was noted, and 1432 singletons were delivered from the VT pregnancy group before cardiac activity could be registered. Using the Poisson model, the adjusted risk ratio (aRR) was used to estimate the incidence of PTB, LBW, SGA and perinatal mortality, in the pregnancies of two types of VT compared with singleton pregnancies after correction for potential confounding factors.

MAIN RESULTS AND THE ROLE OF CHANCE

The vanishing of a co-twin after the registration of cardiac activity was associated with an increased risk of perinatal mortality when compared with the group of singleton pregnancies (0.5% vs 0.2%; P = 0.006); this association still existed after adjustment for potential confounders (aRR 2.19, 95% CI 1.12-4.30; P = 0.023). Furthermore, it was significantly associated with a higher risk of PTB (all cycles aRR 2.00, 95% CI 1.77-2.24; P < 0.001; fresh transfer aRR 2.06, 95% CI 1.78-2.38; P < 0.001; frozen transfer aRR 1.87, 95% CI 1.52-2.28; P < 0.001), LBW (all cycles aRR 2.47, 95% CI 2.12-2.88; P < 0.001; fresh transfer aRR 2.50, 95% CI 2.07-3.02; P < 0.001; frozen transfer aRR 2.39; 95% CI 1.83-3.12; P < 0.001) and SGA (all cycles aRR 1.56, 95% CI 1.35-1.80; P < 0.001; fresh transfer aRR 1.53, 95% CI 1.29-1.81; P < 0.001; frozen transfer aRR 1.62, 95% CI 1.24-2.11; P < 0.001). However, prior to the presence of cardiac activity, the vanishing of a co-twin was not associated with a higher risk of perinatal mortality (all cycles aRR 0.71, 95% CI 0.17-2.92; P = 0.636; fresh cycles aRR 0.51, 95% CI 0.07-3.70; P = 0.502; frozen cycles aRR 1.29, 95% CI 0.17-9.66; P = 0.803), PTB (all cycles aRR 1.11, 95% CI 0.91-1.34; P = 0.301; fresh cycles aRR 1.10, 95% CI 0.87-1.39; P = 0.447; frozen cycles aRR 1.13, 95% CI 0.81-1.58; P = 0.467), LBW (all cycles aRR 1.19, 95% CI 0.91-1.55; P = 0.207; fresh cycles aRR 1.08, 95% CI 0.77-1.51; P = 0.668; frozen cycles aRR 1.45, 95% CI 0.93-2.25; P = 0.100) and SGA (all cycles aRR 1.09, 95% CI 0.89-1.35; P = 0.405; fresh cycles aRR 0.97, 95% CI 0.75-1.26; P = 0.839). Pregnancies involving the two types of VT were significantly different in terms of PTB (all cycles aRR 1.80, 95% CI 1.45-2.24; P < 0.001; fresh cycles aRR 1.88, 95% CI 1.44-2.45; P < 0.001; frozen cycles aRR 1.65, 95% CI 1.13-2.40; P = 0.009), LBW (all cycles aRR 2.08, 95% CI 1.55-2.79; P < 0.001; fresh cycles aRR 2.32, 95% CI 1.61-3.36; P < 0.001; frozen cycles aRR 1.65, 95% CI 1.01-2.70; P = 0.046) and SGA (all cycles aRR 1.70, 95% CI 1.36-2.11; P < 0.001; fresh cycles aRR 1.87, 95% CI 1.42-2.45; P < 0.001).

LIMITATIONS, REASONS FOR CAUTION

The present data are not able to differentiate between co-twin demise occurring in the first or second trimester. Because the second trimester ultrasound scan is not an integral aspect of IVF assessment, this information was not available in the database.

WIDER IMPLICATIONS OF THE FINDINGS

Adverse perinatal outcomes in ART babies can be avoided by replacing one embryo at a time. It is possible to apply selective single embryo transfer strategy for all while maintaining acceptable success rates.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the National Natural Science Foundation of China for Young Scholars (Reference number: 31801251). No competing interests to declare.

TRIAL REGISTRATION NUMBER

not applicable.

Single embryo transfer improve the perinatal outcome in singleton pregnancy

Background and objectives: Most of previous studies are comparing the perinatal outcome on singleton babies. There has been no study evaluating the possible effect of singleton embryo transfer on the perinatal outcomes in initial singleton pregnancy resulting from fresh embryo transfer. The purpose of our study is to access the effect of embryo transfer number on obstetric and perinatal risks in order to examine the role of single embryo transfer on perinatal outcomes on initial singleton pregnancy.Materials and methods: This study is a retrospective cohort study and analyzed 6439 fresh embryo transfer women. 1647 initial singleton pregnancy patients were divided into one of the following three groups according to the embryo transfer number: group A (n = 94): single embryo transfer (SET); group B (n = 1321): double embryo transfer (DET); group C (n = 262): triple embryo transfer (TET). The miscarriage rate and the ectopic pregnancy rate was compared between group A and group B, group C. 1273 live birth patients were divided into three groups too. The obstetrics outcomes and perinatal outcomes between group A and group B, group C.Results: There were 94 singleton pregnancy patients in unselective single embryo transfer. Comparing with double embryo transfer, the early miscarriage rate was higher, but late miscarriage rate, ectopic rate, and live birth rate were comparable between two groups. The obstetrics outcomes were comparable between single embryo transfer and other two groups. Although there was no significant difference between group A and other two groups, preterm birth rate, extremely preterm birth rate, low-birth weight rate and very low-birth weight rate increased with the increase of embryo transfer number. The mean delivery weight was highest in singleton babies in single embryo transfer group. It is higher in group A comparing with group B (3440.4 versus 3320.7 g) and comparing with group C (3440.4 versus 3277.4 g).Conclusions: Single embryo transfer was associated with a better perinatal outcome such as preterm birth and low-birth weight in a singleton pregnancy. The mean birth weight was significantly higher in single embryo transfer group too. Single embryo transfer is a reasonable option to reach the goal of in vitro-fertilization - a healthy singleton neonate.

Comparison of Perinatal Outcomes of Singletons Following Vanishing Twin Phenomenon and Singletons with Initial Single Gestational Sac Conceived Following Assisted Reproductive Technology: A Retrospective Analysis

Aim:

The aim of the study was to compare the perinatal outcomes between singletons following vanishing twin phenomenon and singletons arising from initial single gestational sac following assisted reproductive technology (ART) treatment.

Setting and Design:

This was a retrospective cohort study.

Materials and Methods:

A retrospective cohort study included analysis of all singleton births following ART over a period of 7 years (January 2010 –December 2016). All women who underwent fresh or frozen embryo ART cycles were followed up. The study population included all singleton births following spontaneous reduction of one of the gestational sacs in dichorionic diamniotic twin pregnancies. The perinatal outcome of this group was compared with those of singletons arising from the initial single gestational sac.

Results:

A total of 521 singleton births were recorded during the study period. In the study group, 72 singleton births had spontaneous reduction of one of the gestational sacs (vanishing twin group) and the remaining 449 had an initial single gestational sac. The risk for low birth weight (LBW) (14/72, 19.4% vs. 96/449, 21.6%) and preterm birth (PTB) (17/72, 23.6% vs. 134/449, 29.8%) was not significantly different between those singletons who had spontaneous reduction from two gestational sacs to single sac compared to those with initial single sac. The miscarriage rate was significantly lower in vanishing twin group compared to control group (7/84, 8.3% vs. 157/622, 25.2%; P = 0.01). The subgroup analysis based on spontaneous reduction occurring before or after the appearance of the embryonic pole also showed similar risk of PTB (11/41, 26.8.% vs. 9/31, 29.0%) and LBW (7/41, 17.1% vs. 9/31, 29.0%).

Conclusion:

Perinatal outcomes in singleton live births following vanishing twin phenomenon are similar to those pregnancies with an initial single gestational sac following ART.

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.