Monochorionic and dichorionic twin pregnancies discordant for fetal anencephaly: a systematic review of prenatal management options

Pregnancy outcomes of foetal reduction from twin to singleton gestation compared to ongoing twin gestations: a systematic review and meta-analysis

BACKGROUND

Foetal reduction, which involves selectively terminating one or more foetuses in a multiple gestation pregnancy, has become more common. This systematic review and meta-analysis aims to assess and compare pregnancy outcomes of foetal reduction from twin to singleton gestation to ongoing twin gestations.

METHODS

A comprehensive search of electronic databases (MEDLINE, EMbase, Cochrane Library, CINAHL and PsycINFO) was done for studies published until 15 April 2023. The outcomes analysed included gestational diabetes mellitus (DM), hypertension, caesarean delivery, foetal loss, perinatal death, preterm birth (PTB), intrauterine growth restriction (IUGR), preterm prelabour rupture of membranes (PPROM) and birth weight.

RESULTS

A total of 13 studies comprising 1241 cases of twin to singleton foetal reduction gestation were compared to 20,693 ongoing twin gestations. Our findings indicate that foetal reduction was associated with a significantly lower risk of developing maternal gestational DM (odds ratio [OR] = 0.40, 95% confidence interval [CI] 0.27-0.59) and hypertension (OR = 0.36, 95% CI 0.23-0.57) compared to the control group. Incidence rate of caesarean delivery (OR = 0.65, 95% CI 0.53-0.81) after foetal reduction was significantly lower compared to ongoing twin gestations. There was a 63% lower chance of PTB before 37 weeks of pregnancy. However, there was no significant association between foetal reduction and outcomes such as foetal loss, perinatal death, IUGR and PPROM.

CONCLUSIONS

Our findings suggest that foetal twin to singleton reduction entails potential benefits as compared to ongoing twin gestations. Further well planned studies are needed to explore underlying mechanisms to understanding of the outcomes associated with foetal reduction procedures and inform clinical decision-making for pregnant individuals and healthcare providers alike.

Perinatal outcomes between immediate vs deferred selective termination in dichorionic twin pregnancies with fetal congenital anomalies: a French multicenter study

BACKGROUND

Because selective termination for discordant dichorionic twin anomalies carries a risk of pregnancy loss, deferring the procedure until the third trimester can be considered in settings where it is legal.

OBJECTIVE

To determine whether perinatal outcomes were more favorable following deferred rather than immediate selective termination.

STUDY DESIGN

A French multicenter retrospective study from 2012 to 2023 on dichorionic twin pregnancies with selective termination for fetal conditions, which were diagnosed before 24 weeks gestation. Pregnancies with additional risk factors for late miscarriage were excluded. We defined 2 groups according to the intention to perform selective termination within 2 weeks after the diagnosis of the severe fetal anomaly was established (immediate selective termination) or to wait until the third trimester (deferred selective termination). The primary outcome was perinatal survival at 28 days of life. Secondary outcomes were pregnancy losses before 24 weeks gestation and preterm delivery.

RESULTS

Of 390 pregnancies, 258 were in the immediate selective termination group and 132 in the deferred selective termination group. Baseline characteristics were similar in both groups. Overall survival of the healthy co-twin was 93.8% (242/258) in the immediate selective termination group vs 100% (132/132) in the deferred selective termination group (P<.01). Preterm birth <37 weeks gestation was lower in the immediate than in the deferred selective termination group (66.7% vs 20.2%; P<.01); preterm birth <28 weeks gestation and <32 weeks gestation did not differ significantly (respectively 1.7% vs 0.8%; P=.66 and 8.26% vs 11.4%; P=.36). In the deferred selective termination group, an emergency procedure was performed in 11.3% (15/132) because of threatened preterm labor, of which 3.7% (5/132) for imminent delivery.

CONCLUSION

Overall survival after selective termination was high regardless of the gestational age at which the procedure was performed. Postponing selective termination until the third trimester seems to improve survival, whereas immediate selective termination reduces the risk of preterm delivery. Furthermore, deferred selective termination requires an expert center capable of performing the selective termination procedure on an emergency basis if required.

First report of surgery for anencephaly in twin pregnancies: Technical notes and postoperative management

Anencephaly, the most severe form of neural tube defect, has no known cure, and in most cases, patients die before or shortly after birth. To date, no surgical intervention has been reported in the management of anencephaly. This study presents a case of dichorionic-diamniotic twin pregnancy in which 1 twin was anencephalic and describes the surgical management of this complex case. We aimed to share the problems experienced during the follow up of a patient who survived for a long time after surgery. We also aimed to highlight several clinical issues, including the challenges of managing anencephaly in twin pregnancies, problems experienced during the follow up process in our case, diagnosis of brain death in anencephaly cases, and ethical dilemmas related to organ donation. This case is notable because of the challenging nature of the surgical procedure and complexity of postoperative care. By highlighting the difficulties encountered during the follow up period, we hope to provide insights to health professionals that can inform the management of similar cases in the future.

Maternal outcome of selective feticide due to fetal anomaly in late trimester: A retrospective 10 years' experience in Taiwan

BACKGROUND

Feticide was suggested to avoid delivering children with abnormalities. Recently, twin pregnancies have increased. Selective feticide was proposed to achieve a good outcome of pregnancy. This study aimed to evaluate the performance of feticide in twin pregnancy with fetal anomaly.

METHODS

This was a retrospective study enrolled from 2009 to 2018. A total of 68 pregnancies with fetal anomalies received feticide. Potassium chloride was injected into the left ventricle to induce fetal asystole. Maternal and fetal characteristics of 16 dichorionic twins were documented to compare before and after 24th gestational week.

RESULTS

All pregnant women received feticide without any maternal or fetal complication. The reasons for choosing feticide were divided into four groups, including morphologic defect (61.8%), genetic-chromosomal abnormality (30.9%), obstetrical complication (5.9%), and maternal request (1.5%). Mean gestational age at delivery was significantly higher in dichorionic twins who underwent selective feticide before than after 24th gestational week (36.7 vs 33.4, p = 0.04).

CONCLUSION

Intracardiac injection of potassium chloride was effective for feticide and safe for mothers and fetuses. Selective feticide served as an alternative approach for twin pregnancy with fetal anomaly after sufficient discussion.

Multifetal Gestations: Twin, Triplet, and Higher-Order Multifetal Pregnancies: ACOG Practice Bulletin, Number 231

The incidence of multifetal gestations in the United States has increased dramatically over the past several decades. For example, the rate of twin births increased 76% between 1980 and 2009, from 18.9 to 33.3 per 1,000 births (1). However, after more than three decades of increases, the twin birth rate declined 4% during 2014-2018 to 32.6 twins per 1,000 total births in 2018 (2). The rate of triplet and higher-order multifetal gestations increased more than 400% during the 1980s and 1990s, peaking at 193.5 per 100,000 births in 1998, followed by a modest decrease to 153.4 per 100,000 births by 2009 (3). The triplet and higher-order multiple birth rate was 93.0 per 100,000 births for 2018, an 8% decline from 2017 (101.6) and a 52% decline from the 1998 peak (193.5) (4). The long-term changes in the incidence of multifetal gestations has been attributed to two main factors: 1) a shift toward an older maternal age at conception, when multifetal gestations are more likely to occur naturally, and 2) an increased use of assisted reproductive technology (ART), which is more likely to result in a multifetal gestation (5). A number of perinatal complications are increased with multiple gestations, including fetal anomalies, preeclampsia, and gestational diabetes. One of the most consequential complications encountered with multifetal gestations is preterm birth and the resultant infant morbidity and mortality. Although multiple interventions have been evaluated in the hope of prolonging these gestations and improving outcomes, none has had a substantial effect. The purpose of this document is to review the issues and complications associated with twin, triplet, and higher-order multifetal gestations and present an evidence-based approach to management.

Management of monochorionic twins discordant for structural fetal anomalies

OBJECTIVE

To review the perinatal management and outcomes of monochorionic twin pregnancies (MC) discordant for congenital anomalies (DCA).

METHODS

Retrospective, study of all MC DCA cases referred to our tertiary referral center from 1997 to 2018. We excluded cases complicated with twin-to-twin transfusion syndrome, twin anemia-polycythemia sequence, twin reversed arterial perfusion sequence or selective intra-uterine growth restriction. Patients were counseled about the possibility of expectant (EM) or interventional management (selective feticide [SF] or termination of the entire pregnancy [TOP]).

RESULTS

One hundred eight of 4157 (2.6%) MC pregnancies were discordant for anomaly. Fifty two of 108 n(48.1%) underwent SF at a mean gestational age of 31.4 ± 5.9 weeks while 52/108(48.1%) opted for EM. Livebirth rate of the healthy co-twin was similar between the two groups (SF: 88.5% vs EM: 82.7%, P = .87). In the SF group, six healthy co-twins (6/52, 11.5%) died 5.3 ± 3.1 days after SF of the abnormal co-twin. In the EM group, in-utero demise of the abnormal twin occurred in 9 of 52 (17.3%) of the cases and was followed by the spontaneous demise of the healthy co-twin in 4 of 9 (44.4%) of these cases.

CONCLUSION

Selective feticide does not seem to significantly alter survival of the healthy co-twin compared to EM.

Transabdominal fetal reduction: a report of 124 cases

To prevent fetal loss, preterm delivery, and perinatal morbidity of multifetal pregnancies (MPs), fetal reduction (FR) is offered to some patients. We retrospectively analysed the data of 124 MPs that underwent transabdominal FR to twin (n = 63) and singleton (n = 61) pregnancies at a mean gestational age of 12 + 6 weeks between December 2006 and January 2018. FR was performed transabdominally with the injection of potassium chloride into the intracardiac or intrathoracic space of the fetus or fetuses after ultrasound screening for nuchal translucency and anatomical defects. The initial number of embryos were 48 twins, 63 triplets, 11 quadruplets, and 2 quintuplets. The procedure-related pregnancy loss rate was 0.8% (1/124), the overall pregnancy loss rate was 2.4% (3/124), the fetal loss rate was 1.6% (2/124), and the neonatal death rate was 0.8% (1/124). The baby take-home rates were 96% for twin pregnancies and 96.7% for singletons. This study shows that transabdominal FR is an effective and safe procedure with a pregnancy loss rate of 2.4%.Impact statementWhat is already known on this subject? The incidence of multifetal pregnancies has increased over the years. Because multifetal pregnancies increase perinatal morbidity and mortality due to prematurity, fetal reduction is offed to some patients.What the results of this study add? The results of this study add to the growing body of research on fetal reduction. The study showed that transabdominal fetal reduction is a safe procedure with a pregnancy loss rate of 2.4%.What the implications are of these findings for clinical practice and/or further research? The results of this study can be used in counselling couples with multifetal pregnancies who are considering fetal reduction. Further research is needed to confirm the current findings.

Perinatal outcomes in dichorionic diamniotic twins with multifetal pregnancy reduction versus expectant management: A systematic review and meta-analysis

BACKGROUND

Published findings on perinatal outcomes of multifetal pregnancy reduction (MPR) of dichorionic diamniotic (DCDA) twin pregnancy to singleton are controversial. We performed a meta-analysis to appraise the effects of MPR of DCDA twin pregnancy versus expectant management on perinatal outcomes.

METHODS

Four electronic databases were searched from their inception to June 15, 2019, to identify publications that appraised MPR before 15 weeks of gestation. Studies reporting perinatal outcomes of both MPR of DCDA twin pregnancy to singleton and expectant management were considered. The relative risks (RRs) and mean differences with 95% confidence intervals (CIs) were pooled using a random-effects model.

RESULTS

Six studies involving 7398 participants showed that MPR of DCDA twin pregnancy to singleton was associated with a lower risk of preterm birth (5 studies with 7297 participants; RR: 0.30, 95% CI: 0.22-0.40; P < .001) and higher birth weight (4 studies with 5763 participants; mean differences: 548.10 g, 95% CI: 424.04-672.15; P < .001) than expectant management; there was no difference in the occurrence of miscarriages (5 studies with 7355 participants; RR: 1.57, 95% CI: 0.90-2.75; P = .11). Sensitivity analysis showed that all the results were stable and reliable, with the omission of 2 studies with serious risk of bias.

CONCLUSION

Compared to expectant management, MPR of DCDA twin pregnancy to singleton prevents preterm birth and low birth weight, without increasing the risk of miscarriages. Regarding perinatal morbidity related to preterm birth, MPR can be reserved as a remediation measure to improve the perinatal outcomes of DCDA twin pregnancies.

Transabdominal selective feticide in dichorionic twins: Ten years' experience at a single center

AIM

The present study investigates the procedure-related fetal loss rate and obstetrical outcomes of selective feticide in dichorionic twins.

METHODS

We retrospectively analyzed the data of 44 cases of dichorionic twins. Two different indications for selective feticide were set: (i) the presence of genetic or congenital anomaly; and (ii) an obstetrical indication specified as a past maternal history of preterm delivery that caused fetal death or cerebral palsy of the child. Primarily, data on procedure-related fetal loss and obstetrical outcomes were retrieved. Additionally, data on obstetrical outcomes by reduction time and by indication of SF were obtained.

RESULTS

Selective feticide was performed in 44 cases - specifically, in 23 cases with genetic or congenital anomaly and in 21 cases with obstetrical indications. The median gestational age at delivery was 38 + 4 weeks. One pregnancy loss (2.3%, 1/44) occurred within 4 weeks after the procedure. The overall pregnancy loss rate throughout the pregnancy term was 2.3% (1/44). When selective feticide was performed at 15 weeks and beyond, the birth weight was significantly decreased compared with when selective feticide was performed earlier than 15 weeks.

CONCLUSION

Transabdominal ultrasound-guided selective feticide in dichorionic twins is an effective and safe procedure. If a patient desires to maximize her chances of having a healthy child and decrease the risk of prematurity, the option of selective feticide should be considered in certain cases of twin pregnancies. Selective feticide may be a reasonable alternative to expectant management or termination of the whole twin pregnancy.

Expectant management in di-chorionic pregnancies complicated by discordant anomalous twin

Fetal malformations are more frequent in twins than in singletons. The aim of our study was to define the influence of a malformed twin on di-chorionic pregnancy outcomes. We performed a retrospective cohort study of di-chorionic pregnancies delivered between 2000 and 2015. Exclusion criteria were: both twins affected by fetal malformations, double intra-uterine fetal death in pregnancies without fetal malformation, selective feticide and therapeutic pregnancy termination. We compared maternal and fetal outcomes of di-chorionic pregnancies not complicated by fetal malformations with pregnancies affected by a single malformed fetus with conservative management. We included 642 di-chorionic pregnancies: 56 (case group, 8.7%) with one twin affected by a malformation (20 minor, 36 major ones), 586 (control group, 91.3%) without fetal malformation. No differences were found on maternal and not malformed co-twin outcomes when compared to pregnancies with no malformation; case vs control group presented similar rates of preeclampsia (8.9% vs. 10.8%, respectively), intrauterine growth restriction (7.1% vs. 9.4%) and composite adverse neonatal outcomes (19.6% vs. 15.1%). No case of fetal death in not malformed co-twin was reported. Expectant management could be a safe option for both mother and co-twin in case of di-chorionic twin pregnancy complicated by only one malformed fetus.

Outcome of Twin Pregnancies Complicated by a Neural Tube Defect

Twin pregnancies discordant for neural tube defects (NTD) is a management dilemma. Risks of preterm delivery from polyhydramnios must be balanced with the risks of selective termination (ST) of the anomalous fetus. We investigated the prevalence of twin pregnancies discordant for NTD and the rate of pregnancy complications in our institution over a 10-year period. Cases were obtained by searching the hospital ultrasound database and findings were confirmed by expert review of ultrasound images. Outcomes of ST and expectant management were assessed. Each unaffected co-twin was assigned to three consecutive twin pregnancy controls matched by chorionicity and maternal age. Primary outcome was birth before 34 weeks' gestation. Secondary outcomes were small for gestational age, mode of delivery, neonatal unit admission, and neonatal death. In total, 13 pregnancies were identified as potential cases. Of these, 11 were included in the analysis: 9 dichorionic diamniotic and 2 monochorionic diamniotic twins. Seven cases had ST and four were managed expectantly. We found 100% (4/4) of expectantly managed pregnancies delivered <34 weeks compared with 14% (1/7) of the ST group (p = .015). Polyhydramnios complicated three expectantly managed pregnancies and one pregnancy in the ST group. The birthweight SD score of all unaffected co-twins was ≥-2. The case-control analysis showed a higher rate of polyhydramnios in twin pregnancies discordant for NTD compared with controls, but little evidence for differences between groups in delivery rates <34 weeks, birthweight, neonatal unit admission, or neonatal death. ST warrants serious consideration to avoid potential complications to the unaffected co-twin.

Perinatal Outcome of Discordant Anomalous Twins: A Single-Center Experience in a Developing Country

A dramatic increase in twin pregnancies has been observed in the past few decades, primarily related to assisted reproductive techniques (ART) and increased average maternal age during pregnancy. Multiple pregnancies, compared to singleton pregnancies, are associated with greater perinatal morbidity and mortality. The present study evaluated the perinatal outcomes of pregnancies with discordant anomalous twins in a tertiary maternity ward in a developing country. Data were retrospectively collected from the Instituto Fernandes Figueira/FIOCRUZ, Brazil between January 2002 and December 2014. We identified 74 twin pregnancies with discordant anomalous twins. Final data analysis was based on 40 pregnancies. Congenital defects were classified according to the International Classification of Diseases: ICD-10: the digestive system was responsible in 27 (34%) cases; the central nervous system was responsible in 18 (22%) cases; the urinary tract was responsible in 14 (17%) cases; and the circulatory system was responsible in 14 (17%) cases. A total of 19 deaths occurred during the study period, and delivery before 30.4 weeks was a significant prediction of fetal death (p = .01). The presence of hydrops in the affected fetus was related to a higher number of deaths in healthy fetuses and contributed to a worse prognosis. The presence of this condition was the cause of 12 (55.6%) deaths in healthy fetuses. A 10 times higher risk of death of a normal co-twin was observed in cases of death of the anomalous twin (p = .002, OR 10.55, 95% CI: 1.9–58.52).

Pregnancy outcome after fetal reduction in women with a dichorionic twin pregnancy

STUDY QUESTION

What are the pregnancy outcomes for women with a twin pregnancy that is reduced to a singleton pregnancy?

SUMMARY ANSWER

Fetal reduction of a twin pregnancy significantly improves gestational age at birth and neonatal birthweight, however at an increased risk of pregnancy loss and preterm delivery.

WHAT IS KNOWN ALREADY

Women with a multiple pregnancy are at increased risk for preterm delivery. Fetal reduction can be considered in these women.

STUDY DESIGN, SIZE, AND DURATION

Retrospective cohort study of 118 women with a twin pregnancy reduced to a singleton pregnancy between 2000 and 2010.

PARTICIPANTS/MATERIALS, SETTING, AND METHODS

We compared the outcome of pregnancy in consecutive women with a dichorionic twin pregnancy that was reduced to a singleton pregnancy to that of women with a dichorionic twin pregnancy that was managed expectantly and women with a primary singleton pregnancy. Reductions were performed between 10-23(6/7) weeks' gestation by intracardiac or intrathoracic injection of potassium chloride, mostly for congenital anomalies. We compared median gestational age, pregnancy loss <24 weeks, preterm delivery <32 weeks, neonatal birthweight and perinatal deaths.

MAIN RESULTS AND THE ROLE OF CHANCE

We studied 118 women with a twin pregnancy that was reduced to a singleton, 818 women with an ongoing dichorionic twin pregnancy and 611 women with a primary singleton pregnancy. Loss of the entire pregnancy <24 weeks and preterm delivery occurred significantly more in the reduction group compared with the ongoing twin group (11.9 versus 3.1% <24 weeks, P< 0.001 and 18.6 versus 11.5% <32 weeks, respectively, P < 0.001). In the reduction group, the percentage of women without any surviving child was significantly higher compared with the ongoing twin and primary singleton group (14.4, 3.4 and 0.7%, respectively, P < 0.001). Median gestational age was 38.9 weeks (interquartile range (IQR) 34.7-40.3) for reduced pregnancies, 37.1 weeks (IQR 35.3-38.1) for ongoing twin pregnancies and 40.1 (IQR 39.1-40.9) for primary singletons (P < 0.001 for all comparisons).

LIMITATIONS, REASONS FOR CAUTION

The main limitations of the study were its retrospective character, and the fact that indications for reduction were heterogeneous.

WIDER IMPLICATIONS OF THE FINDINGS

In women with a dichorionic twin pregnancy fetal reduction increases median gestational age only at considerable risk of complete early pregnancy loss.

STUDY FUNDING/COMPETING INTERESTS

The study was not funded. None of the authors has conflicts of interest.

[Selective termination of pregnancy for monochorionic twins: a national survey of professional practice]

OBJECTIVES

Selective Termination of Pregnancy (STOP) for discordant fetal condition in monochorionic twin pregnancy is a rarely performed procedure raising technical and ethical considerations. There are no epidemiological data available in France concerning STOP and no guideline or scientific consensus on how or when to perform has been published.

MATERIALS AND METHODS

We conducted a study of national practice using a declarative questionnaire sent by e-mail to each medical coordinator of every 48 Multidisciplinary Center for Prenatal Diagnosis in France. The questions focused on the issues of 2010 and 2011. Two reminders were sent in case of no answer.

RESULTS

The response rate to the questionnaire was 56 %; 81 % of centers have experienced at least once during the two years 2010-2011 a discordant fetal anomaly in monochorionic twin pregnancy. Only 59 % of centers perform all the techniques of STOP. When interruption of the umbilical blood flow is considered, bipolar forceps coagulation is the most used (75 %). Achieving STOP during a cesarean section is a common practice (75 % of centers). Locoregional anesthesia is the preferred mode of anesthesia for STOP.

DISCUSSION AND CONCLUSION

STOP on monochorionic twin pregnancy is not practiced in all Multidisciplinary Center for Prenatal Diagnosis in France. The most widely practiced and most studied technique is bipolar forceps coagulation. The option of an expectant management should always be considered and its risks should be balanced with those of STOP. The practice of STOP during cesarean section is not unusual.

Differences between selective termination of pregnancy and fetal reduction in multiple pregnancy: a narrative review

Although selective termination of pregnancy and fetal reduction in multiple pregnancy both involve the termination in utero of the development of live fetuses, these two procedures are different in several aspects. Nevertheless, several authors tend to amalgamate and confuse their psychosocial consequences and the ethical issues they raise. Therefore, this narrative review, derived from a comparative analysis of 91 articles, shines a light on these amalgamations and confusions, as well as on the medical, contextual, experiential and ethical differences specific to selective termination and fetal reduction.

Dichorionic, diamnionic twin pregnancy discordant for anencephaly: Report of two cases and literature review

Anencephaly is a lethal diagnosis. In the unique situation of a twin pregnancy discordant for anencephaly, early ultrasound diagnosis based on the discrepancy in the appearance of the heads can facilitate management and potentially decrease morbidity and mortality for the unaffected twin. We report two such cases of dichorionic, diamniotic twin pregnancies and provide a review of the literature.

Expectant management in twin pregnancies with discordant structural fetal anomalies

OBJECTIVE

Routine obstetric ultrasound increasingly leads to the detection of structural fetal anomalies. In twin pregnancies with one anomalous twin, counseling on management strategies is complicated.

PATIENTS AND METHODS

Twin pregnancies (n = 212) were referred to a tertiary center between January 2007 and July 2009. In a retrospective analysis, twins discordant for a structural fetal anomaly were compared to twins without anomalies in the prenatal ultrasound. Outcome parameters were survival and gestational age at birth.

RESULTS

Anomalies were seen in at least one fetus of 30 twin pairs. The two pregnancies in which the anomalies were concordant were terminated. Selective feticide was performed in three cases of major but non-lethal anomalies in dichorionic twins. The remaining 25 cases were managed expectantly. In three of these cases, spontaneous fetal demise of the affected fetus was observed. In five cases with major (lethal) anomalies, the pregnant women and their partners opted for non-intervention comfort care after birth for the affected fetus. Median gestational age at delivery was 257 days for twins without structural anomalies and was 254 days (n = 22) for twins with one anomalous fetus. This was not significantly different (Mann Whitney U, p = .69). Again, no difference was found for median gestational age at delivery in normal vs. discordant anomalous dichorionic twins if subdivided for chorionicity (Mann Whitney U, p = .68).

CONCLUSION

In this cohort we describe the request for expectant management by pregnant women and their partners of those twins discordant for major (lethal) anomalies. Expectant management was not associated with increased risk of premature delivery. Fetocide was only opted for in a small number of cases with severe but non-lethal anomalies in dichorionic twins.

Dichorionic twin pregnancy discordant for fetal anencephaly: a case report

Dichorionic twin pregnancy discordant for fetal anencephaly is a serious condition that threatens the normal co-twin's life by causing polyhydramniosis, preterm labor and sudden death of one or both of the fetuses. We report a case of dichorionic twin pregnancy discordant for fetal anencephaly delivered at the 32(nd) week of gestation because of preterm labor and nonreassuring fetal monitoring. The aim of this case report is to summarize management options in this situation.

Twin pregnancies complicated by a single malformed fetus: chorionicity, outcome and management

The objective of this study was to evaluate the impact of one abnormal fetus in a twin pregnancy, to compare impact of chorionicity and clinical outcome of intervention and expectant management. Thirty-seven dichorionic (DC) twins and 18 monochorionic (MC) twins complicated with one malformed fetus were evaluated for gestational age, birthweight and perinatal outcome. Six hundred and forty-two twin pregnancies were evaluated in the database. The control groups consisted of 429 DC and 86 MC twins without anomalous fetus. Mean birthweight and gestational age at birth for DC control group were (n = 429; 2137g and 34.71 weeks), DC study group, n = 37; 2117g (p = .338) and 33.97 weeks (p = .311), and DC study group with major malformations, n = 30; 2019g (p = .289) and 33.3 weeks (p = .01), and showed only significance for gestational age. There was no statistical significance between MC control group, n = 86; 2097g and 34.93 weeks, and MC study group, n = 18; 2237g (p = .338), and 34.42 weeks (p = .502). Because of limited data, the preliminary evaluation for expectant management and intervention, and survival of at least one normal fetus showed no impact. We conclude that, although, all DC twin pregnancies have a risk for preterm delivery, DC twins complicated with major malformation of one twin, have a lower mean gestational age at birth. Preliminary results for intervention does not improve fetal outcome for DC and MC twins and needs further evaluation with greater studies of impact or review.

[Discordant anomaly in twin pregnancy]

The risk of fetal loss is multiplied by 4 in monochorionic pregnancies by comparison with dichorionic one. The incidence of selective growth retardation (sIUGR) is between 12.5 to 25%. This variation is explained by the mixture between pure twin-to-twin transfusion syndrome (TTTS) and pregnancies without TTTS but with a pure sIUGR. The ability to diagnose prenatally sIUGR is low; the positive predictive value is only 37% (EL4). The umbilical flow velocity waveforms with absent diastolic flow (Type II) or with diastolic intermittent flow (Type III) is clearly a strong risk factor of mortality of the IUGR and also a risk factor of leucomalacia of the bigger fetus (EL3). The observed incidence of malformations in twins is 4.05% versus 2.38% for singletons (OR=1.7 [IC 95% 1.47-1.97]). Furthermore, the rate of fetal malformations is higher in monochorionic pregnancies by comparison with dichorionic one, 6.33% versus 3.43% (OR=1.8 [IC 95% 1.3-2.5]) (EL3). In the majority of the cases, the malformation is concerning only one fetus. The most frequent malformations are those of the central nervous system by comparison with singletons, those of the urinary tract and the cardiovascular malformations. Monozygotic pregnancies are not necessarily phenotypically and genetically identical. In situation of asymmetrical malformation, it is necessary to propose fetal karyotype of the malformed fetus. In case aneuploidy of the malformed fetus, secondarily it will be necessary to explore the other apparently normal one. Uniparental disomy should be suspected in such situation (EL3). In TRAP sequence, an intensive follow up should be organised with serial measurement of the respective size of the acardiac fetus and the normal one, Doppler exploration should be done to look for early sign of cardiac decompensation (expert viewpoint). In dichorionic pregnancies, when the malformation is threatening the whole pregnancy like anencephaly, a selective feticide allow a prolongation of the pregnancy, but with a risk of fetal loss of 8% and a risk of iatrogenic prematurity of 12%. In such situation, it could be wise to evaluate the evolution or to wait until the third trimester to undergo the procedure (EL3). In monochorionic pregnancies, in the same situation of anencephalic fetus the best option is bipolar cord coagulation. The result seems to be better after 18 weeks of gestation (EL4). There is a 20% risk of premature rupture of membrane. In the up to date analysis of the literature, there is no formal indication of selective feticide expect case of TRAP sequence with cardiac decompensation of the normal fetus. The very special situation of sIUGR is the object of a randomized trial. In all cases the active participation of the patients to the therapeutic option is mandatory (expert viewpoint).