Monochorionic quadramniotic and triamniotic pregnancies following single embryo transfers: two case reports and a review of the literature

Cellular mechanisms of monozygotic twinning: clues from assisted reproduction

BACKGROUND

Monozygotic (MZ) twins are believed to arise from the fission of a single fertilized embryo at different stages. Monochorionic MZ twins, who share one chorion, originate from the splitting of the inner cell mass (ICM) within a single blastocyst. In the classic model for dichorionic MZ twins, the embryo splits before compaction, developing into two blastocysts. However, there are a growing number of ART cases where a single blastocyst transfer results in dichorionic MZ twins, indicating that embryo splitting may occur even after blastocyst formation.

OBJECTIVE AND RATIONALE

For monochorionic MZ twins, we conducted a comprehensive analysis of the cellular mechanisms involved in ICM splitting, drawing from both ART cases and animal experiments. In addition, we critically re-examine the classic early splitting model for dichorionic MZ twins. We explore cellular mechanisms leading to two separated blastocysts in ART, potentially causing dichorionic MZ twins.

SEARCH METHODS

Relevant studies including research articles, reviews, and conference papers were searched in the PubMed database. Cases of MZ twins from IVF clinics were found by using combinations of terms including 'monozygotic twins' with 'IVF case report', 'ART', 'single embryo transfer', or 'dichorionic'. The papers retrieved were categorized based on the implicated mechanisms or as those with unexplained mechanisms. Animal experiments relating to MZ twins were found using 'mouse embryo monozygotic twins', 'mouse 8-shaped hatching', 'zebrafish janus mutant', and 'nine-banded armadillo embryo', along with literature collected through day-to-day reading. The search was limited to articles in English, with no restrictions on publication date or species.

OUTCOMES

For monochorionic MZ twins, ART cases and mouse experiments demonstrate evidence that a looser ICM in blastocysts has an increased chance of ICM separation. Physical forces facilitated by blastocoel formation or 8-shaped hatching are exerted on the ICM, resulting in monochorionic MZ twins. For dichorionic MZ twins, the classic model resembles artificial cloning of mouse embryos in vitro, requiring strictly controlled splitting forces, re-joining prevention, and proper aggregation, which allows the formation of two separate human blastocysts under physiological circumstances. In contrast, ART procedures involving the transfer of a single blastocysts after atypical hatching or vitrified-warmed cycles might lead to blastocyst separation. Differences in morphology, molecular mechanisms, and timing across various animal model systems for MZ twinning can impede this research field. As discussed in future directions, recent developments of innovative in vitro models of human embryos may offer promising avenues for providing fundamental novel insights into the cellular mechanisms of MZ twinning during human embryogenesis.

WIDER IMPLICATIONS

Twin pregnancies pose high risks to both the fetuses and the mother. While single embryo transfer is commonly employed to prevent dizygotic twin pregnancies in ART, it cannot prevent the occurrence of MZ twins. Drawing from our understanding of the cellular mechanisms underlying monochorionic and dichorionic MZ twinning, along with insights into the genetic mechanisms, could enable improved prediction, prevention, and even intervention strategies during ART procedures.

REGISTRAITON NUMBER

N/A.

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.

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.

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.

Analysis of 122 triplet and one quadruplet pregnancies after single embryo transfer in Japan

RESEARCH QUESTION

What is the prevalence of triplet and quadruplet pregnancies after single embryo transfer (SET) in Japan.

DESIGN

A retrospective observational study was conducted on 274,605 pregnancies after 937,848 SET cycles in registered assisted reproductive technology (ART) data from the Japanese ART national registry database between 2007 and 2014. A questionnaire survey of ART centres was also conducted. Data on pregnancies with embryo division into three or more after SET were analysed.

RESULTS

According to the Japanese ART national registry database, SET resulted in 109 triplet pregnancies (0.04% of pregnancies), and the questionnaire reports from 31 centres revealed 33 triplet and one quadruplet pregnancies. After exclusion of 20 duplicated cases, 122 triplet and one quadruplet pregnancies included 46 monochorionic (one gestational sac [37.4%]), 18 dichorionic (two gestational sacs [14.6%]) and 59 trichorionic pregnancies (three gestational sacs [48.0%]). Compared with singleton pregnancies, patients with monozygotic triplet or quadruplet pregnancies were less frequently diagnosed with unexplained infertility (P = 0.004), more often received gonadotrophin injections for ovarian stimulation in 39 cases with information available (P = 0.021) and underwent more blastocyst transfers and assisted hatching (P = 0.002 and P < 0.001, respectively). The proportion of live birth, defined as at least one baby born, excluding induced abortion, was 64.6% (73/116 pregnancies) of monozygotic triplet or quadruplet pregnancies.

CONCLUSIONS

Combined Japanese ART national registry and survey data revealed 122 triplet and one quadruplet pregnancies, the majority after cryopreserved embryo transfer. Most were conceived after blastocyst transfer and often after assisted hatching, which are potential risk factors for zygotic splitting.

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.

Successful quintuplet pregnancy of monochorionic male quadruplets and single female after double embryo transfer: case report and review of the literature

OBJECTIVE

To report a rare case of quintuplets with monochorionic male quadruplets and a single female after two-blastocyst transfer.

DESIGN

Case report.

SETTING

University teaching hospital.

PATIENT(S)

A 37-year-old gravida 1, para 1, presenting after two-embryo IVF with monochorionic male quadruplets and a single female.

INTERVENTION(S)

Ultrasound examinations and cesarean delivery.

MAIN OUTCOME MEASURE(S)

Successful delivery of five live-born infants at 28 weeks and 6 days of gestation for preterm labor.

RESULT(S)

The patient was diagnosed with quintuplets consisting of monochorionic male quadruplets and a single female after the placement of two embryos in blastocyst stage. She was followed closely with ultrasound examinations and hospitalized at 23 weeks' gestation. Cesarean delivery was performed at 28 weeks and 6 days of gestation, with eventual discharge of all infants in healthy condition.

CONCLUSION(S)

This case represents successful assisted reproductive technology quintuplets with monochorionic quadruplets and a co-sibling. Higher-order monozygotic pregnancies with monochorionic quadruplets are exceedingly rare and a potential complication of IVF.

Dichorionic triplets following frozen-thawed poor-stage embryo transfer: a report of two cases and a review

BACKGROUND

We describe two cases of dichorionic triplet pregnancy after a frozen-thawed poor-stage embryo transfer. A 39-year-old and a 41-year-old woman underwent ART treatment. The first patient underwent intracytoplasmic sperm injection (ICSI) at 34 years of age, and two frozen-thawed poor-stage embryos were transferred at 39 years of age with assisted hatching, resulting in a trichorionic triamniotic triplet pregnancy. The second patient underwent ICSI, and two poor-grade blastocysts were transferred followed by assisted hatching, resulting in a dichorionic triamniotic triplet pregnancy. In the first case, the heartbeat of one monozygotic twin fetus had stopped on day 48 post-transfer (9 weeks 2 days), resulting in a dichorionic diamniotic twin pregnancy. A healthy boy and girl were delivered by elective caesarean section at 36 weeks, 5-days gestation. In the second case, the patient underwent selective reduction of the monochorionic twins, resulting in a single pregnancy that was vaginally delivered without any problems at 38 weeks 0-days gestation.

SHORT CONCLUSIONS

Numerous factors may be associated with the development of a monochorionic pregnancy; however, controversies still remain. The present morphological grading for embryos is insufficient for inhibiting the development of a monochorionic pregnancy.

Dynamics of a Pregnancy When Two Become Four: A Case Report and Literature Review

The incidence of pregnancies with multiple gestational sacs has increased with the use of assisted reproductive technology because more than one embryo is frequently transferred. The splitting of one or more embryos further complicates the pregnancy. Some of these complications include intrauterine fetal death, growth restriction, discordant birth weight, and preterm delivery. Monozygotic twins suffer from a few unique complications including twin-twin transfusion syndrome, twin reversed arterial perfusion sequence, and twin anemia-polycythemia sequence. Therefore, patients should be informed about the possible obstetric complications regarding monozygotic twinning after embryo transfer as poor obstetric/perinatal outcome is significantly impacted by the presence of an "extra" fetus. The etiology of monozygotic twinning is not fully understood although a few risk factors have been identified. The objective of this communication is to report successful management of a pregnancy resulting in four gestational sacs after transfer of two embryos on day-three post retrieval.

Standards of Care in infertility in Europe

Evidence-based medicine is the principal approach to medical practice. There are several debatable issues in infertility, which require clarification. Over the past 20 years, reliable methodology has been developed for the management of infertile couples. This includes high quality diagnostic and therapeutic procedures, which are applied in highly specialised infertility centres. The European Board and College of Obstetrics and Gynaecology (EBCOG) has published Standards of Care for Women's Health in Europe, which should be the cornerstone for the clinicians and service providers in the European Union to establish common protocols within their centres. Each infertility treatment should result in the highest possible success rate and all appropriate measures for the patient's safety should be in place. The treatment protocols should minimise risk of complications, such as ovarian hyperstimulation syndrome (OHSS). The current use of GnRH agonists to trigger final follicle maturation has provided the means for avoiding this syndrome. Additionally, multiple pregnancy rates are still high in assisted reproductive technology (ART). These rates should be reduced by the adoption of single embryo transfer during IVF treatment and by the proper monitoring of ovulation induction protocols. EBCOG Standards of Care for infertility and assisted conception treatment derived from the best available evidence should underpin the provision of high quality infertility services in European countries.

Do ARTs affect the incidence of monozygotic twinning?

STUDY QUESTION

Does the manipulation of gametes or embryos during ARTs increase the risk for monozygotic twinning (MZT)?

SUMMARY ANSWER

Frozen embryo transfer (ET) is associated with a lower MZT rate, while blastocyst culture is associated with an increased risk of monozygotic pregnancy.

WHAT IS KNOWN ALREADY

Monozygotic twins have a higher risk for perinatal complications. Although an increased incidence of monozygotic pregnancies after ART has been previously reported, data regarding the possible impact of different laboratory procedures are conflicting.

STUDY DESIGN, SIZE, DURATION

All clinical pregnancies after single ET carried out in our centre between 2004 and 2013 (n = 6096) were retrospectively analysed for the incidence of MZT. The effect of different laboratory procedures on the incidence of MZT was evaluated.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The following ART risk factors were assessed: maternal age, type of ET (fresh versus frozen), zona pellucida (ZP) manipulation (specifically, ICSI, embryo biopsy and assisted hatching), use of donor oocytes, embryo stage at time of ET (cleavage, compaction, early or advanced blastocyst) and culture media.

MAIN RESULTS AND THE ROLE OF CHANCE

The overall MZT rate was 2.2% (136/6096). Frozen ET was associated with a significant reduction in MZT incidence (adjusted odds ratio (aOR) 0.48, 95% CI 0.29-0.80), while blastocyst transfer (early or advanced blastocyst) was associated with a significant increase in MZT risk (aOR 2.70, 95% CI 1.36-5.34; aOR 2.05, 95% CI 1.29-3.26, respectively). No significant differences were found between the MZT and singleton (non-MZT) groups regarding maternal age, the use of different ZP manipulation techniques, not type of culture media used.

LIMITATION, REASONS FOR CAUTION

This study is limited by its retrospective nature and the fact that monozygosity was not confirmed by genetic testing. Furthermore, since monozygotic pregnancy is a rare event, other ART parameters that may influence its incidence could not be assessed during our analysis.

WIDER IMPLICATION OF THE FINDINGS

Our findings warrant future studies designed to investigate the association between specific ART procedures and MZT, namely the potential risk of blastocyst transfer to increase MZT.

STUDY FUNDING/COMPETING INTERESTS

No external funding was used for this study. There are no conflicts of interest.