Monozygotic twinning after assisted reproductive technologies: a case report of asymmetric development and incidence during 19 years in an international group of in vitro fertilization clinics

First case of dichorionic diamniotic triplet pregnancy after single blastocyst transfer

Multiple pregnancies are associated with significant maternal, fetal, and neonatal risks, including prematurity, low birth weight, pre-eclampsia, anemia, postpartum hemorrhage, intrauterine growth restriction, neonatal morbidity, and increased neonatal and infant mortality rates. Assisted reproductive technology (ART) treatments should prioritize efforts to reduce such events, resisting patient demand for the transfer of multiple embryos at each transfer to increase success rates. Extended culture, embryo selection, and single blastocyst transfer can mitigate the risk of high-order multiple pregnancies. Intriguingly, elective single-embryo transfer (eSET) greatly reduces, but does not completely eliminate, the likelihood of multiple gestations. The occurrence of monozygotic twinning (MZT) gives rise to identical twins. It is more prevalent in women undergoing in vitro fertilization (IVF) compared with natural conception. In fact, the reported risks of monozygotic twinning in IVF and natural conception are 1.7 and 0.4%, respectively. The factors suspected to increase the risk of MZT in IVF are multiple embryo transfer, micromanipulation, and extended in vitro culture. Determining chorionicity and amnionicity is crucial in the assessment of multiple pregnancies during the first-trimester ultrasound examination. Dichorionic twins result from embryo splitting within 3 days after fertilization, while monochorionic twins occur when the splitting takes place between 4 and 8 days after fertilization. These timings are suggested by observations carried out in natural pregnancies. In ART, there is evidence of dichorionic twins derived from single embryo transfer (SET). Here, we report a case of dichorionic diamniotic triplets after a single blastocyst transfer occurred in our center. To our knowledge, this is the first case documented so far.

Molecular Characterization of a Rare Case of Monozygotic Dichorionic Diamniotic Twin Pregnancy after Single Blastocyst Transfer in Preimplantation Genetic Testing (PGT)

Preimplantation genetic testing (PGT) is widely used to select unaffected embryos, increasing the odds of having a healthy baby. During the last few decades, it was accepted that monozygotic dichorionic diamniotic twin pregnancies occurred from the embryo splitting before Day 3 postfertilization according to Corner’s dogma. Hence, the occurrence of a dichorionic diamniotic twin pregnancy after a single blastocyst transfer was considered a dizygotic pregnancy resulting from blastocyst transfer and concurrent natural fertilization. In our study, we have provided for the first time molecular proof that a single blastocyst transfer can result in a monozygotic dichorionic diamniotic twin pregnancy, invalidating Corner’s dogma. In this case, we recommend systematically assessing the genetic status of dichorionic twins after single blastocyst transfer using prenatal diagnosis to exclude the risk from a potential concurrent spontaneous pregnancy and to ensure that both fetuses are unaffected. To achieve this goal, we have developed here an innovative noninvasive prenatal diagnosis by exclusion of paternal variants with droplet digital PCR, maximizing the reliability of genetic diagnosis. Further multicentric prospective studies using genetic testing are now required to establish the rate of blastocyst splitting leading to dichorionic pregnancy in PGT and to identify the risk factors.

Dichorionic quadruplet pregnancy comprising monozygotic triplets and singleton after intracytoplasmic sperm injection and transfer of two fresh embryos: a case report

Monozygotic triplet pregnancies are very rare in assisted reproductive technology, and the relationship between monozygotic multiple pregnancies and several assisted reproductive techniques, including blastocyst transfer, remains unclear. Here, the case of a 28-year-old female patient with dichorionic quadruplet pregnancy following intracytoplasmic sperm injection and transfer of two day-3 fresh embryos, without assisted hatching, is reported. At 7 weeks following embryo transfer, the dichorionic quadruplet pregnancy, comprising monozygotic monochorionic triamniotic (MCTA) triplets plus a singleton, was detected by a transabdominal ultrasound scan. After counselling, the patient underwent selective reduction of the MCTA triplet pregnancy at 7 weeks after embryo transfer. The remaining singleton pregnancy was uneventful, resulting in a live birth at 38⁺ weeks. As the predictors of monozygotic multiple gestations remain poorly characterized, clinicians and patients should give great consideration to the risks associated with monozygotic multiple pregnancies, even if the patient has not undergone blastocyst transfer.

On the origin of zygosity and chorionicity in twinning: evidence from human in vitro fertilization

Assisted reproduction is presumed to increase monozygotic twin rates, with the possible contribution of laboratory and medical interventions. Monozygotic dichorionic gestations are supposed to originate from the splitting of an embryo during the first four days of development, before blastocyst formation. Single embryo transfers could result in dichorionic pregnancies, currently explained by embryo splitting as described in the worldwide used medical textbooks, or concomitant conception. However, such splitting has never been observed in human in vitro fertilization, and downregulated frozen cycles could also produce multiple gestations. Several models of the possible origins of dichorionicity have been suggested. However, some possible underlying mechanisms observed from assisted reproduction seem to have been overlooked. In this review, we aimed to document the current knowledge, criticize the accepted dogma, and propose new insights into the origin of zygosity and chorionicity.

Monozygotic dichorionic-diamniotic pregnancies following single frozen-thawed blastocyst transfer: a retrospective case series

BACKGROUND

The primary aim of the study is to report cases of monozygotic dichorionic-diamniotic (DC-DA) pregnancies after single frozen-thawed blastocyst transfer.

METHODS

This is a retrospective case series. All single frozen-thawed blastocyst transfer cycles performed between June 2013 and December 2018 at the Shanghai Ji Ai Genetics and IVF Institute, Obstetrics and Gynecology Hospital, Fudan University, Shanghai, China, were reviewed retrospectively. We included frozen embryo transfer (FET) cycles which clinical pregnancy was confirmed with multiple gestational sacs showed on ultrasonography at around 6 to 7 weeks of gestation. We then conducted an in-depth analysis to further exclude cases which contained newborns of different genders or natural FET cycles.

RESULTS

Five thousand four hundred fifteen frozen-thawed single blastocyst transfer cycles were preformed between June 2013 and December 2018 at the Shanghai Ji Ai Genetics and IVF Institute, Obstetrics and Gynecology Hospital, Fudan University, Shanghai, China. Of these, fourteen women underwent a single blastocyst transfer and then achieved clinical pregnancy with an ultrasound diagnosis of multi-chorionic pregnancy. With one natural cycle FET excluded, we finally included thirteen single blastocyst transfer cycles performed in down-regulated controlled FET or hormone replacement FET, in which the possibility of concurrently spontaneous pregnancy was extremely small. These included 13 cases reveal the phenomenon of monozygotic DC-DA twinning after single blastocyst transfer, which challenges the classical theory that only monochorionic pregnancy could happen after 3 days of fertilization.

CONCLUSION

This case series suggest that single blastocyst transfer could result DC-DA pregnancies during IVF treatment.

Successful monozygotic triplet pregnancy after a single blastocyst transfer following in vitro maturation of oocytes from a woman with polycystic ovary syndrome: a case report

Background

Although women with polycystic ovarian syndrome (PCOS)-related sub-fertility are high responders to controlled ovarian stimulation, it is difficult to obtain mature oocytes in these women. Therefore, in vitro maturation (IVM), which is the technique of letting the contents of the ovarian follicles and the oocytes inside mature in vitro, has often been proposed in such women. We describe the first successful delivery of monozygotic triplets resulting from transfer of a single blastocyst following IVM of oocytes.

Case presentation

A 32-year-old nulligravida female with PCOS underwent IVM. She underwent vitrified-warmed single blastocyst transfer following IVM, and a dichorionic triamniotic triplet pregnancy was confirmed at 8 weeks. Healthy triplets were delivered by cesarean section at 33 weeks’ gestation. This is the first case of monozygotic triplets derived from IVM oocytes that were successfully delivered. The determination of chorionicity and amnionicity is generally supposed until 3 days after fertilization, and no division or splitting of her embryo was observed on transfer. Interestingly, her embryo might have split after the transfer, resulting in a dichorionic triamniotic triplet pregnancy.

Conclusions

Patients should be informed of a possible increased risk of monozygotic multiple pregnancies after single embryo transfer following IVM.

Risk factors for monozygotic twinning after in vitro fertilization: a systematic review and meta-analysis

OBJECTIVES

To establish the risk factors for monozygotic twin (MZT) and monochorionic twin (MCT) pregnancies after in vitro fertilization (IVF).

DESIGN

Systematic review and meta-analysis.

SETTING

Not applicable.

PATIENT(S)

Women who achieved MZT and non-MZT pregnancies through IVF.

INTERVENTION(S)

Systematic search of Medline from January 1995 to October 2018 with cross-checking of references from relevant articles in English.

MAIN OUTCOME MEASURE(S)

Possible risk factors for MZT or MCT pregnancies after IVF, comprising extended embryo culture, insemination method (conventional IVF and intracytoplasmic sperm injection [ICSI]), embryo biopsy for preimplantation genetic testing for aneuploidies or for monogenic/single-gene defects (PGT-A or PGT-M) programs, assisted hatching (AH), oocytes donation, female age, and embryo cryopreservation.

RESULT(S)

A total of 40 studies were included. Blastocyst transfer compared with cleavage-stage embryo transfer, and female age <35 years were associated with a statistically significant increase in the MZT and MCT pregnancy rate after IVF: (23 studies, OR 2.16, 95% CI, 1.74-2.68, I²=78%; 4 studies, OR 1.29; 95% CI, 1.03-1.62, I²=62%; and 3 studies, OR 1.90, 95% CI, 1.21-2.98, I²=59%; 2 studies, OR 2.34; 95% CI, 1.69-3.23, I²=0, respectively). Conventional IVF compared with ICSI and assisted hatching were associated with a statistically significantly increased risk of MZT pregnancy (9 studies, OR 1.19, 95% CI, 1.04-1.35, I²=0; 16 studies, OR 1.17, 95% CI, 1.09-1.27, I²=29%, respectively). Embryo biopsy for PGT-A or PGT-M, embryo cryopreservation, and oocytes donation were not associated with MZT pregnancies after IVF.

CONCLUSION(S)

Blastocyst transfer is associated with an increased risk of both MZT and MCT pregnancies after IVF. Further evidence is needed to clarify the impact of female age, insemination method and AH on the investigated outcomes.

Multi-chorionic pregnancies following single embryo transfer at the blastocyst stage: a case series and review of the literature

OBJECTIVE

To report cases of in vitro fertilization-frozen embryo transfer (IVF-FET) with single blastocyst transfer resulting in di- or tri-chorionic pregnancies, and to review the literature on monozygotic, multi-chorionic pregnancies originating at the blastocyst stage.

DESIGN

Retrospective case series and literature review.

MATERIALS AND METHODS

All in vitro fertilization cycles (fresh, frozen, autologous, and donor oocyte) performed between June 2012 and June 2017 at the University of California, San Francisco Center for Reproductive Health, were reviewed retrospectively. Cycles with cleavage-stage embryos or transfer of more than one blastocyst were excluded. Cycles were analyzed to determine if clinical pregnancy occurred with the presence of two or more gestational sacs noted on initial ultrasound. An in-depth chart review was performed with further exclusions applied that would lend credence to dizygosity rather than monozygosity such as fetal/neonatal sex discordance, fresh embryo transfer, and natural cycle FET (in which concomitant spontaneous pregnancy could have occurred). Demographic, clinical and IVF-FET cycle characteristics of the resulting patients were collected. Additionally, a review of the English language literature was performed (PUBMED, PMC) using the search words monozygotic twins, dichorionic diamniotic, in vitro fertilization, and single embryo transfer in order to identify cases of DC-DA monozygotic twinning from 1978 to 2017. Resulting articles were reviewed to eliminate all cases of dizygosity and day 3 embryo transfers. We obtained the following data from the literature search: basic patient demographics, type of fertilization, type and day of embryo transferred, number of embryos transferred, gestational ultrasound details, presence of any genetic testing if performed after delivery, and number of live births.

RESULT(S)

Two thousand four hundred thirty-four women underwent fresh or frozen single embryo transfer between June 2012 and June 2017 at the University of California, San Francisco Center for Reproductive Health. Of these, 11 women underwent a single blastocyst transfer with subsequent clinical pregnancies identified as multi-chorionic gestations. Four were in downregulated controlled FET cycles, in which concomitant spontaneous pregnancy could not have been possible. We then reviewed all cases of monozygotic dichorionic-diamniotic (DC-DA) splitting in IVF patients reported in the literature from 1978 to 2017. These eight cases demonstrate monozygotic splitting after the blastocyst stage, which challenges the existing dogma that only monochorionic twins can develop after day 3 post-fertilization.

CONCLUSION(S)

The accepted theory of monozygotic twinning resulting from the splitting of an embryo per a strict post-fertilization timing protocol must be re-examined with the advent of observed multi-chorionic pregnancies resulting from single blastocyst transfer in the context of IVF.

Risk of Monozygotic Twins After Assisted Reproduction: A Population-Based Approach

BACKGROUND

Recent studies have suggested that ovarian stimulation and assisted reproductive techniques (ART) may increase the frequency of monozygotic twins. In this article, we present the analysis of the estimated frequency of twin deliveries following in vitro fertilization (IVF) in Lombardy during the period 2010-2014 for a total of 450,949 pregnancies.

METHOD

This is a population-based study using data from the regional data base of Lombardy, a northern Italian region with a population of about 10 million inhabitants. During the considered period, a total of 461,424 single or multiple births were registered in Lombardy. After exclusion of triplets or more pregnancies, the total number of twin deliveries, in separate strata of like and unlike sex pregnancies twin deliveries, were obtained and the rate of twin deliveries was computed according to spontaneous and non-spontaneous conception and type of ART. Further, estimates of dizygotic or monozygotic twin births were calculated using Weinberg's methods.

RESULTS

The frequency of twins deliveries was 1.24/100 deliveries after natural conception and 20.05 after assisted conception. The estimated rates of monozygotic twins was 0.45 and 0.72/100 (95% CI: 0.58-0.91) deliveries after natural and assisted conception, respectively. This difference was statistically significant (p < .05).

CONCLUSION

the present population based study suggests that the risk of monozygotic twin is about 60% higher among assisted than after natural conception.

Estimating the Risk of Monochorionic Twins in IVF Pregnancies From the Perspective of a Prenatal Diagnosis Unit

The aim of the present work was to estimate the risk of monochorionic twin (MCT) pregnancies in in vitro fertilization (IVF) cycles using data from a prenatal diagnosis unit. This was a retrospective cross-sectional study reporting on the frequency of IVF pregnancies among women attending a prenatal diagnosis service specifically dedicated to the management of monochorionic pregnancies. The observed rate was compared with the local regional rate of IVF births (2.2%). A binomial distribution model was used to calculate the 95% CI of proportions. One hundred and forty-five monochorionic pregnancies were selected. Ten of these were achieved with IVF, corresponding to a rate of 6.9% (95% CI: 3.5–11.8), significantly higher than the background rate in the local population of 2.2%. When considering exclusively monochorionic pregnancies achieving delivery of two viable newborns (n = 132), the number of IVF pregnancies was nine (6.8%, 95% CI: 3.7–12.5). We did not detect major differences in pregnancy outcome between IVF and natural monochorionic pregnancies, with the exception of the proportion of newborns with a neonatal birth < 2,500 g (100% vs. 80%, p = .03). In conclusion, data obtained from the perspective of a prenatal diagnosis unit suggest that women undergoing IVF face a 3- to 4-fold increased risk of monochorionic pregnancies.

Monochorionic diamniotic in vitro fertilization twins have a decreased incidence of twin-to-twin transfusion syndrome

OBJECTIVE

To compare the incidence of twin-to-twin transfusion syndrome (TTTS) in spontaneous versus IVF-conceived twin pregnancies.

DESIGN

Retrospective multicenter study.

SETTING

University-affiliated tertiary medical centers.

PATIENT(S)

Women admitted for 11-14 week's scan between January 1997 and July 2013 who were diagnosed with monochorionic (MC) diamniotic twin pregnancies.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Mode of conception, TTTS.

RESULT(S)

The study cohort included 327 pregnant women with live MC diamniotic twins. Of them, 284 (86.9%) and 43 (13.1%) were spontaneous and IVF conceived, respectively. The mean maternal age was significantly higher in IVF compared with in spontaneously conceived pregnancies (33.8 ± 5.5 vs. 31.6 ± 5.4, respectively). Thirty-seven twins (11.3%) had TTTS, of whom 36/284 (12.7%) versus 1/43 (2.3%) were spontaneously and IVF conceived, respectively. The mean week of delivery was significantly lower in MC twins diagnosed with TTTS compared with those without TTTS (32.7 ± 3.3 vs. 35.5 ± 2.5, respectively). Furthermore, there was a significantly higher birthweight discordancy in twins diagnosed with TTTS compared with those without (20.6% vs. 11%, respectively).

CONCLUSION(S)

The significantly lower proportion of TTTS found in IVF-conceived twins may suggest a different embryological process that lies at the core of IVF conception of monozygotic twinning.

Discordant Growth of Monozygotic Twins Starts at the Blastocyst Stage: A Case Study

Discordant growth is a common complication of monochorionic/diamniotic pregnancies; in approximately 50% of cases, the cause is unknown. The case presented here suggests that discordant growth of monozygotic twins could start during preimplantation development. Two inner cell masses (ICMs) within the same blastocyst may originate in uneven splitting of a single “parental” ICM, or the two ICMs may be formed independently de novo. We studied the transcriptomes of two morphologically distinct ICMs within a single blastocyst using high-resolution RNA sequencing. The data indicated that the two ICM were at different stages of development; one was in the earliest stages of lineage commitment, while the other had already differentiated into epiblast and primitive endoderm. IGF1-mediated signaling is likely to play a key role in ICM growth and to be the major driver behind these differences.

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Two ICMs within the same blastocyst were at different stages of development

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IGF1-mediated signaling is likely to be the major driver behind these differences

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The expression pattern of YAP1 is different in human embryos from in the mouse