First-trimester ultrasound determination of chorionicity in twin gestations using the lambda sign: a systematic review and meta-analysis

Society for Maternal-Fetal Medicine Consult Series #72: Twin-twin transfusion syndrome and twin anemia-polycythemia sequence

Thirty percent of spontaneously occurring twins are monozygotic, of which two-thirds are monochorionic, possessing a single placenta. A common placental mass with shared intertwin placental circulation is key to the development and management of complications unique to monochorionic gestations. In this Consult, we review general considerations and a contemporary approach to twin-twin transfusion syndrome and twin anemia-polycythemia sequence, providing management recommendations based on the available evidence. The following are the Society for Maternal-Fetal Medicine recommendations: (1) we recommend routine first-trimester sonographic determination of chorionicity and amnionicity (GRADE 1B); (2) we recommend that ultrasound surveillance for twin-twin transfusion syndrome begin at 16 weeks of gestation for all monochorionic-diamniotic twin pregnancies and continue at least every 2 weeks until delivery, with more frequent monitoring indicated with clinical concern (GRADE 1C); (3) we recommend that routine sonographic surveillance for twin-twin transfusion syndrome minimally include assessment of amniotic fluid volumes on both sides of the intertwin membrane and evaluation for the presence or absence of urine-filled fetal bladders, and ideally incorporate Doppler study of the umbilical arteries (GRADE 1C); (4) we recommend fetoscopic laser surgery as the standard treatment for stage II through stage IV twin-twin transfusion syndrome presenting between 16 and 26 weeks of gestation (GRADE 1A); (5) we recommend expectant management with at least weekly fetal surveillance for asymptomatic patients continuing pregnancies complicated by stage I twin-twin transfusion syndrome, and consideration for fetoscopic laser surgery for stage I twin-twin transfusion syndrome presentations between 16 and 26 weeks of gestation complicated by additional factors such as maternal polyhydramnios-associated symptomatology (GRADE 1B); (6) we recommend an individualized approach to laser surgery for early- and late-presenting twin-twin transfusion syndrome (GRADE 1C); (7) we recommend that all patients with twin-twin transfusion syndrome qualifying for laser therapy be referred to a fetal intervention center for further evaluation, consultation, and care (Best Practice); (8) after laser therapy, we suggest weekly surveillance for 6 weeks followed by resumption of every-other-week surveillance thereafter, unless concern exists for post-laser twin-twin transfusion syndrome, post-laser twin anemia-polycythemia sequence, or fetal growth restriction (GRADE 2C); (9) following the resolution of twin-twin transfusion syndrome after fetoscopic laser surgery, and without other indications for earlier delivery, we recommend delivery of dual-surviving monochorionic-diamniotic twins at 34 to 36 weeks of gestation (GRADE 1C); (10) in twin-twin transfusion syndrome pregnancies complicated by posttreatment single fetal demise, we recommend full-term delivery (39 weeks) of the surviving co-twin to avoid complications of prematurity unless indications for earlier delivery exist (GRADE 1C); (11) we recommend that fetoscopic laser surgery not influence the mode of delivery (Best Practice); (12) we recommend that prenatal diagnosis of twin anemia-polycythemia sequence minimally require either middle cerebral artery Doppler peak systolic velocity values >1.5 and <1.0 multiples of the median in donor and recipient twins, respectively, or an intertwin Δ middle cerebral artery peak systolic velocity >0.5 multiples of the median (GRADE 1C); (13) we recommend that providers consider incorporating middle cerebral artery Doppler peak systolic velocity determinations into all monochorionic twin ultrasound surveillance beginning at 16 weeks of gestation (GRADE 1C); and (14) consultation with a specialized fetal care center is recommended when twin anemia-polycythemia sequence progresses to a more advanced disease stage (stage ≥II) before 32 weeks of gestation or when concern arises for coexisting complications such as twin-twin transfusion syndrome (Best Practice).

Non-invasive cell-free DNA prenatal screening for trisomy 21 as part of primary screening strategy in twin pregnancy

OBJECTIVES

The performance of non-invasive prenatal screening using cell-free DNA testing of maternal blood in twin pregnancy is underevaluated, while serum marker-based strategies yield poor results. This study aimed to assess the performance of non-invasive prenatal screening for trisomy 21 in twin pregnancy as a first-tier test. Secondary objectives were to assess its failure rate and factors associated with failure.

METHODS

This retrospective cohort study included twin pregnancies in which non-invasive prenatal screening using cell-free DNA was performed as the primary screening strategy between May 2017 and October 2019. We used the NIPT VeriSeq® test for in-vitro diagnosis and set a fetal fraction cut-off of 4% for monochorionic pregnancies and 8% for dichorionic ones. Clinical data and pregnancy outcome were collected from physicians or midwives via a questionnaire or were retrieved directly on-site. We calculated the performance of non-invasive cell-free DNA screening for trisomy 21, analyzed its failure rate and assessed potentially associated factors.

RESULTS

Among 1885 twin pregnancies with follow-up, there were six (0.32%) confirmed cases of trisomy 21. The sensitivity of non-invasive prenatal screening for trisomy 21 was 100% (95% CI, 54.1-100%) and the false-positive rate was 0.23% (95% CI, 0.06-0.59%). The primary failure rate was 4.6%, with 4.0% being due to insufficient fetal fraction. A successful result was obtained for 65.4% of women who underwent a new blood draw, reducing the overall failure rate to 2.8%. Maternal body mass index, gestational age at screening as well as chorionicity were significantly associated with the risk of failure.

CONCLUSION

This study provides further evidence of the high performance, at an extremely low false-positive rate, of non-invasive prenatal screening in twins as part of a primary screening strategy for trisomy 21. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Structural Anomalies in Multifetal Gestations

Multifetal gestations are at increased risk for structural anomalies relative to singletons. Determination of chorionicity is critical, as the risk is highest for monochorionic pregnancies. In a singleton gestation, counseling is structured around optimization of fetal outcomes and careful consideration of the patient's choices in management decisions. However, in multifetal gestations affected by a fetal anomaly, complex counseling with consideration for the pregnancy as a whole is necessary. We review the incidence of structural anomalies in twins and highlight unique considerations including selective termination for discordant anomalies. We emphasize the role of shared decision making between provider and patient.

The High-Risk Profile of Selective Growth Restriction in Monochorionic Twin Pregnancies

The present review aims to provide a critical appraisal of the sonographic diagnosis and follow-up and to evaluate the optimal clinical management of monochorionic twin pregnancies where one of the twins is complicated by selective fetal growth restriction (sFGR). The classification is based on the umbilical artery (UA) diastolic flow reflecting the outcome. If the sFGR twin has positive diastolic flow (Type I) then the prognosis is good, and it does not require close surveillance. Biweekly or weekly sonographic and Doppler surveillance and fetal monitoring are recommended strategies to detect unpredictable complications in type II and type III forms, which are defined by persistently absent/reverse end-diastolic flow (AREDF) or cyclically intermittent absent/reverse end-diastolic flow (iAREDF) in the umbilical waveforms, respectively. The latest forms are associated with an increased risk of unexpected fetal demise of the smaller twin and 10-20% risk of neurological injury in the larger twin in addition to the overall risk of prematurity. The clinical course can be affected by elective fetal therapy ('dichorinization' of the placenta with laser or selective fetal reduction) or elective delivery in the presence of severe fetal deterioration. The prediction of the clinical outcome in complicated cases of type II and III sFGR cases remains elusive. Novel routines in fetal and placental scans in order to predict neurological impairments and unexpected fetal death to optimize the delivery time-point are needed.

Clinician-reported Chorionicity and Zygosity Assignment using single-nucleotide polymorphism-based cell-free DNA Lessons learned from 55,344 Twin Pregnancies

Objective

Prenatal chorionicity assessment relies on ultrasound, which can be confounded by many factors. Noninvasive assessment of zygosity is possible using single nucleotide polymorphism (SNP)‐based cell‐free DNA testing. Our objective was to determine the relationship between provider‐reported chorionicity and SNP‐cfDNA assignment of twin zygosity.

Methods

All twin pregnancy blood samples received by a reference laboratory between September 27, 2017 and September 8, 2021 were included. Chorionicity assignment was requested on the requisition, recorded as; monochorionic (MC), dichorionic, or “don't know”. SNP‐cfDNA zygosity results, monozygotic (MZ) or dizygotic (DZ), were correlated with chorionicity assignment.

Results

59,471 twin samples (median gestational age = 12.0 weeks at draw) were received and analyzed; 55,344 (93.1%) received zygosity assignment. SNP‐cfDNA reported 16,673 (30.1%) MZ and 38,671 (69.9%) as DZ. Provider‐reported chorionicity was compared to the zygosity assignment for each case. Of 6283 provider‐reported MC twins, 318 (5.1%) were reported as DZ using SNP‐cfDNA.

Conclusion(s)

One in 20 suspected MC twin pregnancies were reported as DZ using SNP‐cfDNA. Approximately 30% of 55,344 twin pregnancies were found to be MZ, including cases where chorionicity was unknown. SNP‐cfDNA zygosity assessment is a useful adjunct assessment for twin pregnancies, particularly those reported as MC or without determined chorionicity.

What's already known about the topic?

The assignment of chorionicity early in pregnancy can improve perinatal outcomes of twin pregnancies. Prenatal assessment of chorionicity relies on ultrasound (US), and the accuracy of US can be confounded by many factors, including gestational age (GA) and operator experience. Noninvasive assessment of zygosity is now possible using single nucleotide polymorphism (SNP)‐based cell‐free DNA (cfDNA).

What does this study add?

This is the first population‐based study describing the correlation between cfDNA assessment of zygosity and chorionicity. In 55,344 twin pregnancies, approximately 30% were found to be monozygotic (MZ), including cases where chorionicity was unknown. We found that one in 20 suspected monochorionic (MC) twin pregnancies were reported as dizygotic (DZ) twins (DZ) by SNP‐cfDNA testing. SNP‐cfDNA zygosity assessment is a useful adjunct assessment for twin pregnancies, particularly those reported as MC or without determined chorionicity.

Guideline No. 428: Management of Dichorionic Twin Pregnancies

OBJECTIVE

To review evidence-based recommendations for the management of dichorionic twin pregnancies.

TARGET POPULATION

Pregnant women with a dichorionic twin pregnancy.

BENEFITS, HARMS, AND COSTS

Implementation of the recommendations in this guideline may improve the management of twin pregnancies and reduce neonatal and maternal morbidity and mortality.

EVIDENCE

Published literature was retrieved through searches of PubMed and the Cochrane Library using appropriate controlled vocabulary (e.g., twin, preterm birth). Results were restricted to systematic reviews, randomized controlled trials, controlled clinical trials, and observational studies. There were no date limits, but results were limited to English- or French-language materials.

VALIDATION METHODS

The content and recommendations were drafted and agreed upon by the principal authors. The Board of the SOGC approved the final draft for publication. The authors rated the quality of evidence and strength of recommendations using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. See online Appendix A (Tables A1 for definitions and A2 for interpretations of strong and weak recommendations).

INTENDED AUDIENCE

Obstetricians, family physicians, nurses, midwives, maternal-fetal medicine specialists, radiologists, and other health care providers who care for women with twin pregnancies.

SUMMARY STATEMENTS

RECOMMENDATIONS.

Perinatal outcomes in twin late preterm pregnancies: results from an Italian area-based, prospective cohort study

BACKGROUND

Multiple gestations represent a considerable proportion of pregnancies delivering in the late preterm (LP) period. Only 30% of LP twins are due to spontaneous preterm labor and 70% are medically indicated; among this literature described that 16-50% of indicated LP twin deliveries are non-evidence based. As non-evidence-based delivery indications account for iatrogenic morbidity that could be prevented, the objective of our observational study is to investigate first neonatal outcomes of LP twin pregnancies according to gestational age at delivery, chorionicity and delivery indication, then non evidence-based delivery indications.

METHODS

Prospective cohort study among twins infants born between 34 + 0 and 36 + 6 weeks, in Emilia Romagna, Italy, during 2013-2015. The primary outcome was a composite of adverse perinatal outcomes.

RESULTS

Among 346 LP twins, 84 (23.4%) were monochorionic and 262 (75.7%) were dichorionic; spontaneous preterm labor accounted for 85 (24.6%) deliveries, preterm prelabor rupture of membranes for 66 (19.1%), evidence based indicated deliveries were 117 (33.8%), while non-evidence-based indications were 78 (22.5%). When compared to spontaneous preterm labor or preterm prelabor rupture of membranes, pregnancies delivered due to maternal and/or fetal indications were associated with higher maternal age (p <  0.01), higher gestational age at delivery (p <  0.01), Caucasian race (p 0.04), ART use (p <  0.01), gestational diabetes (p <  0.01), vaginal bleeding (p <  0.01), antenatal corticosteroids (p <  0.01), diagnosis of fetal growth restriction (FGR) (p <  0.01), and monochorionic (p <  0.01). Two hundred twenty-six pregnancies (65.3%) had at least one fetus experiencing one composite of adverse perinatal outcome. Multivariate analysis confirmed that delivery indication did not affect the composite of adverse perinatal outcomes; the only characteristic that affect the outcome after controlling for confounding was gestational age at delivery (p <  0.01). Moreover, there was at least one adverse neonatal outcome for 94% of babies born at 34 weeks, for 73% of those born at 35 weeks and for 46% of those born at 36 weeks (p <  0.01).

CONCLUSION

Our study suggests that the decision to deliver or not twins in LP period should consider gestational age at delivery as the main determinant infants' prognosis. Delivery indications should be accurately considered, to avoid iatrogenic early birth responsible of preventable complications.

Sonographic evaluation of umbilical cord thickness in monochorionic diamniotic twin pregnancies

OBJECTIVE

To develop a nomogram of the thickness of the umbilical cord (UC) and its components in monochorionic diamniotic (MCDA) twin pregnancies.

METHODS

This prospective longitudinal study involved 47 MCDA twin pregnancies (94 fetuses) between 18 and 33 weeks of gestation. Ultrasound assessments of UC cross-sections and measurements of the umbilical cord area (UCA), the umbilical vein area (UVA), the umbilical artery area (UAA), and the Wharton jelly area (WJA) were made. The UC measurements were correlated with gestational ages. Reference values for the gestational ages of MCDA pregnancies were determined and compared with those of dichorionic twins and singletons. The cases which developed selective intrauterine growth restriction were contrasted with normal cases.

RESULTS

A positive correlation was found between all UC components and gestational age and fetal weight. The UCA of MCDA fetuses was significantly larger than that of DC fetuses (P < 0.001) at the expense of a larger WJA (P < 0.001) and similar to that of singleton pregnancies. The MCDA fetuses with an estimated fetal weight below the 10th percentile had a smaller UCA than fetuses with a normal estimated weight (P < 0.001).

CONCLUSION

The MCDA twins exhibited a thicker UC than that of dichorionic twins. This article is protected by copyright. All rights reserved.

Determining chorionicity and amnionicity in twin pregnancies: Pitfalls

Although the accuracy of chorioamnionicity determination in multiple pregnancy is nearly 100%, some pitfalls do exist. These pitfalls may arise from some confusing sonographic appearance or because of certain rare variations of twinning going against the general principles. Pitfalls in chorionicity determination include (1) the disappearance of the twin peak sign with the regression of chorion frondosum and thinning of the intertwin membrane with advancing gestation; (2) fake twin peak sign because of other structures creeping into the intertwin membrane-placental junction; (3) intrauterine septum or synechia being mistaken as a thick intertwin membrane; (4) bipartite placenta in monochorionic twin being misinterpreted as two separate placentas of dichorionic twin; (5) erroneous fetal sex determination in sex chromosome mosaicism, monogenic disorders, and malformed genitalia in one fetus; and (6) rare twinning types such as dizygotic monochorionic twin and sesquizygotic twin. Pitfalls in amnionicity determination are (1) the lack of correlation between the number of yolk sacs and amnionicity and (2) failure to visualize the intertwin membrane because of technical issues.

What fetal medicine specialists should know about the monochorionic placenta

Monochorionic twins are at risk of transfusion imbalances as long as they are connected to the shared placenta during their intrauterine journey. This review article addresses the macroscopic examination of the monochorionic placenta at the time of birth and explains placental dye injection studies to document the vascular anastomoses and placental sharing. We elaborate on the different types of anastomoses, the importance of how the placenta is divided between the twins, and the angioarchitecture in twin-twin transfusion syndrome, twin anemia polycythemia sequence and selective fetal growth restriction.

Introducing a New Predictor of Chorionicity in the Second and Third Trimesters: The “Cleft Sign”

Objective:

The aim of this study was to suggest a new sonographic sign, which could be helpful in the determination of chorionicity in twin pregnancies, during the second and third trimesters.

Materials and Methods:

This was a retrospective study evaluating the sonographic images of 50 women with twin pregnancy. Out of 50 twin pregnancy case reviewed, only 27 were included. Those patient cases that were included were scanned by a single radiologist. The presence of a hypoechoic cleft, in the thickness of placental bulk, could be detected in all of the dichorionic pregnancy cases. This sonographic appearance was referred to as the “cleft sign.”

Results:

The “cleft sign” was present in all the dichorionic diamniotic (DC-DA) twin pregnancy cases, but no similar appearance was seen in the monochorionic diamniotic (MC-DA) twins. Considering this sign, the radiologist was able to correctly diagnose the chorionicity of all 24 patients in the second and third trimester.

Conclusion:

The findings of the present study suggest a possible role for this newly identified “cleft sign.” This sonographic appearance is a hypoechoic cleft in the thickness of placenta, of dichorionic pregnancies, as an indicator of DC twin pregnancy. In this retrospective case analysis, the “cleft sign” was diagnostically significant in the second and third trimesters.

Multifetal Gestations and Associated Perinatal Risks

Along with the rise of assisted reproductive technology, multifetal gestations increased dramatically. Twin pregnancies account for 97% of multifetal pregnancies and 3% of all births in the United States. Twins and higher-order multiples carry increased risks of obstetric, perinatal, and maternal complications; these risks increase with increasing fetal number. Neonatal morbidity and mortality in multifetal gestations is driven primarily by prematurity. Both spontaneous and indicated preterm births are increased in multifetal gestations, and only a limited number of strategies are available to mitigate this risk. No single intervention has been shown to decrease the rate of spontaneous preterm birth in most twin pregnancies. Low-dose aspirin prophylaxis is recommended in all multifetal pregnancies to reduce the risk of preeclampsia and its associated complications. Antenatal management of multifetal gestations depends on chorionicity, which should be established using ultrasonography in the first trimester. Unlike dichorionic twin gestations, monochorionic pregnancies experience unique complications because of their shared vascular connections, and therefore, need frequent ultrasound surveillance. Even uncomplicated twin gestations have higher rates of unanticipated stillbirth compared with singletons. Delivery of twin pregnancies is generally indicated in the late preterm to early term period depending on chorionicity and other clinical factors. For most diamniotic twin pregnancies with a cephalic presenting fetus, vaginal delivery after 32 weeks' gestation is a safe and reasonable option with high rates of success and no increased risk of perinatal morbidity.

Committee Opinion No. 418: The Complete 11-14 Week Prenatal Sonographic Examination

OBJECTIVE

Sonography during the first trimester provides an opportunity to assess a pregnancy in its early stage. This document provides an opinion about the implementation and content of prenatal sonographic examinations at 11-14 weeks gestation in Canada.

TARGET POPULATION

Pregnant women at 11-14 weeks gestation.

BENEFITS, HARMS, AND COSTS

The 11-14 week prenatal sonographic examination can provide important information that may contribute to pregnancy management. It can be used to confirm viability, establish gestational age, determine the number of fetuses, assess the adnexa/ovaries, and, in a multiple pregnancy, assess chorionicity and amnionicity. Scanning also offers an opportunity to detect fetal abnormalities and perform aneuploidy screening by measuring the nuchal translucency thickness. It may be valuable in screening for preeclampsia and other obstetrical disorders (by combining uterine artery Doppler scanning with other bio-clinical markers) and for invasive placentation. There are no physical harms to mother or fetus from offering a routine 11-14 week prenatal sonographic examination, and there are no extra costs for patients.

EVIDENCE

Articles related to routine 11-14 week prenatal sonography were identified in a search of EMBASE and MEDLINE using the search terms first trimester ultrasound, nuchal translucency, and 11-14 week ultrasound. The search included all articles published on the topic until May 2019. Abstracts were reviewed by one author, and articles deemed relevant were then reviewed in full to determine whether to include them in the study. Articles that were not in English and articles that did not pertain to 11-14 week prenatal sonography were excluded.

INTENDED AUDIENCE

This document is intended for sonographers, midwives, family physicians, obstetricians, and maternal-fetal medicine specialists.

Screening, Management and Delivery in Twin Pregnancy

The following AWMF guideline (DGGG/AGG & DEGUM responsible) deals with the diagnosis, screening and management of twins as well as the timing and mode of birth.Twin pregnancies can be classified as dichorionic diamniotic (DC DA), monochorionic diamniotic (MC DA) and monochorionic monoamniotic (MC MA) which are always monochorionic.Twin pregnancies can be concordant (both twins are affected) or discordant (only one twin is affected) for chromosomal defects, malformations, growth restriction and hemodynamic disorders.Chorionicity is the prognostically most significant parameter. Monochorial twins have significantly higher risks of intrauterine morbidity and mortality compared to dichorial twins.In particular, general aspects of twin pregnancies such as dating, determination of chorionicity and amnionicity, the labeling of twin fetuses and the perinatal switch phenomenon are discussed.Routine monitoring of MC and DC twin pregnancies with ultrasound at 11-13^+ 6 weeks of gestation for chromosomal defects, invasive prenatal diagnosis, first-trimester NT or CRL discrepancies, early diagnosis of fetal anatomical defects, and management of twins with abnormalities, including selective fetocide, is described.Second trimester screening and management for preterm birth, intrauterine selective growth restriction (sFGR), classification of monochorial twins with sFGR, and management of the surviving twin after the death of the co-twin are described.Complications exclusively affecting MC twins include Twin to Twin Transfusion Syndrome (TTTS) with the important topics screening, prognosis, complications of laser therapy, timing of delivery, risks for brain abnormalities and delayed neurological development, Twin Anemia-Polycythemia Sequence (TAPS) and Twin Reversed Arterial Perfusion (TRAP) Sequence. This also includes MC MA twins as well as conjoined twins.Finally, the birth mode and time for DC and MC twin pregnancies are described.The information is summarized in 62 recommendations for action, 4 tables and 8 illustrations with comprehensive background texts.The guideline is an international guideline adaptation (ISUOG, NICE) as well as a systematic literature search and is up-to-date.

Changes in the Ultrasonographical Appearance of Intertwin-Dividing Membrane of Monochorionic Diamniotic Twin Pregnancy

Ultrasound determination of chorionicity in the first trimester has a high accuracy, but it is associated with some pitfalls. This report presents changes in ultrasound findings during a monochorionic pregnancy with chorionic membrane folding (CMF). The patient was a 32-year-old woman, gravida 2 para 0. Her transvaginal ultrasonography identified two gestational sacs (GSs) and two embryos at 7 weeks of gestation. At 9 weeks' gestation, an ultrasound image showed a lambda sign at both sides and the interruption of chorionic membranes, resulting in the diagnosis of a monochorionic diamniotic (MCDA) twin pregnancy with CMF. At 11 weeks' gestation, an ultrasound image showed a lambda sign at one portion of the septum and a T sign at another portion. This change suggested that the folded chorionic membrane had partially flattened. At 35 weeks' gestation, an emergency cesarean section was performed. Two healthy male neonates were delivered. Histological placental examination confirmed that the intertwin membrane was composed of two amniotic membranes without a folded chorionic membrane, confirming the diagnosis of a MCDA twin pregnancy. This case presents two important ultrasound chorionicity findings: a monochorionic pregnancy with CMF can show two GSs and a lambda sign and the CMF can flatten or change during the pregnancy.

Additional benefits of three-dimensional ultrasound for prenatal assessment of twins

Three-dimensional ultrasound (3DUS) may provide additional information for prenatal assessment of twins. It may improve the diagnostic confidence of dating, nuchal translucency (NT) and chorionicity assignment in twin pregnancies. The "virtual 3DUS placentoscopy" can guide selective fetoscopic laser photocoagulation (SFLP) to treat twin-twin transfusion syndrome (TTTS). Volumetric assessment of the dysmorphic acardiac twin with the Virtual Organ Computer-aided Analysis (VOCAL) software is more accurate than the conventional ultrasound measurement. Twin anemia polycythemia (TAP) sequence and selective intrauterine growth restriction (sIUGR) may be clinically monitored with 3DUS placental volume (PV) and power Doppler vascular indices. Congenital anomalies are more common in twins. Evaluation of fetal anomalies with 3DUS could assist perinatal management. The 3DUS power Doppler can provide a better understanding of true and false umbilical cord knots, which are commonly found in monoamniotic (MA) twins. Single demise in monochorionic (MC) twin pregnancies can cause severe neurologic morbidity in the surviving co-twin. Prenatal prediction of brain injury in the surviving co-twin with unremarkable neurosonographic examination is difficult. The 3DUS power Doppler may aid in prenatal detection of subtle abnormal cerebral perfusion. Prenatal assessment of conjoined twins with 3DUS is important if emergency postnatal surgical separation is anticipated. There is no significant additional advantage in using real-time 3DUS to guide prenatal interventions. Assessment of the cervix and pelvic floor during twin pregnancies is enhanced with 3DUS. Due to lack of high-quality studies, routine prenatal 3DUS in twin pregnancies needs to be balanced with risks of excessive ultrasound exposure.

Validation of a Single-Nucleotide Polymorphism-Based Non-Invasive Prenatal Test in Twin Gestations: Determination of Zygosity, Individual Fetal Sex, and Fetal Aneuploidy

We analyzed maternal plasma cell-free DNA samples from twin pregnancies in a prospective blinded study to validate a single-nucleotide polymorphism (SNP)-based non-invasive prenatal test (NIPT) for zygosity, fetal sex, and aneuploidy. Zygosity was evaluated by looking for either one or two fetal genome complements, fetal sex was evaluated by evaluating Y-chromosome loci, and aneuploidy was assessed through SNP ratios. Zygosity was correctly predicted in 100% of cases (93/93; 95% confidence interval (CI) 96.1%-100%). Individual fetal sex for both twins was also called with 100% accuracy (102/102; 95% weighted CI 95.2%-100%). All cases with copy number truth were also correctly identified. The dizygotic aneuploidy sensitivity was 100% (10/10; 95% CI 69.2%-100%), and overall specificity was 100% (96/96; 95% weighted CI, 94.8%-100%). The mean fetal fraction (FF) of monozygotic twins (n = 43) was 13.0% (standard deviation (SD), 4.5%); for dizygotic twins (n = 79), the mean lower FF was 6.5% (SD, 3.1%) and the mean higher FF was 8.1% (SD, 3.5%). We conclude SNP-based NIPT for zygosity is of value when chorionicity is uncertain or anomalies are identified. Zygosity, fetal sex, and aneuploidy are complementary evaluations that can be carried out on the same specimen as early as 9 weeks' gestation.

Inpatient vs outpatient management and timing of delivery of uncomplicated monochorionic monoamniotic twin pregnancy: the MONOMONO study

OBJECTIVES

Monoamniotic twin pregnancies are at increased risk of perinatal complications, primarily owing to the risk of cord entanglement. There is no recommendation on whether such pregnancies should be managed in hospital or can be safely managed in an outpatient setting, and the timing of planned delivery is also a subject of debate. The aim of this study was to compare the perinatal outcomes of inpatient vs outpatient fetal surveillance approaches employed among 22 participating study centers, and to calculate the fetal and neonatal death rates according to gestational age, in non-anomalous monoamniotic twins from 26 weeks' gestation.

METHODS

The MONOMONO study was a multinational cohort study of consecutive women with monochorionic monoamniotic twin pregnancies, who were referred to 22 university hospitals in Italy, the USA, the UK and Spain, from January 2010 to January 2017. Only non-anomalous uncomplicated monoamniotic twin pregnancies with two live fetuses at 26 + 0 weeks' gestation were included in the study. In 10 of the centers, monoamniotic twins were managed routinely as inpatients, whereas in the other 12 centers they were managed routinely as outpatients. The primary outcome was intrauterine fetal death. We also planned to assess fetal and neonatal death rates according to gestational age per 1-week interval. Outcomes are presented as odds ratio (OR) with 95% CIs. The main outcome was analyzed using both standard logistic regression analysis, in which each fetus was treated as an independent unit, and a generalized mixed-model approach, with each twin pair treated as a cluster unit, considering that the outcome for a twin is not independent of that of its cotwin.

RESULTS

195 consecutive pregnant women with a non-anomalous uncomplicated monoamniotic twin gestation (390 fetuses) were included. Of these, 75 (38.5%) were managed as inpatients and 120 (61.5%) as outpatients. The overall perinatal loss rate was 10.8% (42/390) with a peak fetal death rate of 4.3% (15/348) occurring at 29 weeks' gestation. There was no significant difference in mean gestational age at delivery (31 weeks), birth weight (∼1.6 kg), or emergency delivery rate between the inpatient and outpatient surveillance groups. Based on generalized mixed-model analysis, there was no statistically significant difference in fetal death rates between inpatient management commencing from around 26 weeks compared with outpatient surveillance protocols from 30 weeks (3.3% vs 10.8%; adjusted OR 0.21 (95% CI, 0.04-1.17)). Maternal length of stay in the hospital was 42.1 days in the inpatient group, and 7.4 days in the outpatient group (mean difference 34.70 days (95% CI, 31.36-38.04 days). From 32 + 0 to 36 + 6 weeks, no fetal or neonatal death in either group was recorded. 46 fetuses were delivered after 34 + 0 weeks, and none of them died in utero or within the first 28 days postpartum.

CONCLUSION

In uncomplicated monoamniotic twins, inpatient surveillance is associated with similar fetal mortality as outpatient management. After 31 + 6 weeks, and up to 36 + 6 weeks, there were no intrauterine fetal deaths or neonatal deaths. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Antenatal intervention for congenital fetal lower urinary tract obstruction (LUTO): a systematic review and meta-analysis

Objective: To evaluate the effectiveness of antenatal intervention for the treatment of congenital lower urinary tract obstruction (LUTO) in improving perinatal survival and postnatal renal function.Methods: Electronic databases were searched from their inception until May 2018. Selection criteria included randomized controlled trials and nonrandomized studies including fetuses with ultrasound evidence of LUTO evaluating antenatal intervention for improving perinatal outcomes. Any type of antenatal bladder drainage technique was analyzed. The primary outcome was perinatal survival. The secondary outcome was postnatal survival with normal renal function. The summary measures were reported as summary odds ratio (OR) with 95% of confidence interval (CI).Results: Ten articles with a total of 355 fetuses were included in the meta-analysis. Inclusion criteria of the selected studies were singleton pregnancy with severe LUTO confirmed on detailed fetal ultrasound examination. Nine studies analyzed the efficacy of vesico-amniotic shunt performed in the second trimester. The overall estimate survival was higher in the vesico-amniotic shunt group compared to the conservative group (OR: 2.54, 95% CI: 1.14-5.67). 64/112 fetuses (57.1%) survived in the vesico-amniotic shunt group compared to 52/134 (38.8%) in the control group. Five studies reported on postnatal renal function between 6 months and 2 years. Rate of good postnatal renal function was higher in the vesico-amniotic shunt group compared to the conservative group (OR: 2.09, 95% CI: 0.74-5.9). Fetal cystoscopy was performed in only two included studies. Overall, 45 fetuses underwent fetal cystoscopy. The perinatal survival was higher in the cystoscopy group compared to the conservative management group (OR: 2.63, 95% CI: 1.07-6.47). Normal renal function was noted in 13/34 fetuses in the cystoscopy group versus 12/61 in the conservative management group at 6 months follow-up (OR: 1.75, 95% CI: 1.05-2.92)Conclusions: Antenatal bladder drainage appears to improve perinatal survival in cases of LUTO.

Maternal steroid therapy for fetuses with immune-mediated complete atrioventricular block: a systematic review and meta-analysis

INTRODUCTION

To explore the effect of maternal fluorinated steroid therapy on fetuses affected by immune-mediated complete atrio-ventricular block (CAVB) in utero.

MATERIAL AND METHODS

Pubmed, Embase, Cinahl, and ClinicalTrials.gov databases were searched. Only studies reporting the outcome of fetuses with immune CAVB diagnosed on prenatal ultrasound without any cardiac malformations and treated with fluorinated steroids compared to those not treated were included. The primary outcome observed was the regression of CAVB; secondary outcomes were need for pacemaker insertion, overall mortality, defined as the occurrence of either intrauterine (IUD) or neonatal (NND) death, IUD, NND, termination of pregnancy (TOP). Furthermore, we assessed the occurrence of all these outcomes in hydropic fetuses compared to those without hydrops at diagnosis. Meta-analyses of proportions using random effect model and meta-analyses using individual data random-effect logistic regression were used to combine data.

RESULTS

Eight studies (162 fetuses) were included. The rate of regression was 3.0% (95%CI 0.2-9.1) in fetuses treated and 4.3% (95%CI 0.4-11.8) in those not treated, with no difference between the two groups (odds ratio (OR): 0.9, 95%CI 0.1-15.1). Pacemaker at birth was required in 71.5% (95%CI 56.0-84.7) of fetuses-treated and 57.8% (95%CI 40.3-74.3) of those not treated (OR: 9, 95%CI 0.4-3.4). There was no difference in the overall mortality rate (OR: 0.5, 95%CI 0.9-2.7) between the two groups; in hydropic fetuses, mortality occurred in 76.2% (95%CI 48.0-95.5) of the treated and in 23.8% (95%CI 1.2-62.3) of the untreated group, while in those without hydrops the corresponding figures were 8.9% (95%CI 2.0-20.3) and 12% (95%CI 8.7-42.2), respectively. Improvement or resolution of hydrops during pregnancy occurred in 76.2% (95%CI 48.0-95.5) of cases treated and in 23.3% (95%CI 1.2-62.3) of those nontreated with fluorinated steroids.

CONCLUSIONS

The findings from this systematic review do not suggest a potential positive contribution of antenatal steroid therapy in improving the outcome of fetuses with immune CAVB.

Pitfalls in assessing chorioamnionicity: novel observations and literature review

Accurate diagnosis of chorioamnionicity in multiple pregnancies is the key to appropriate clinical management of multiple gestation. Although prenatal ultrasound assessment of chorioamnionicity is well established and highly accurate if performed in early pregnancy, exceptions and artifacts arise from anatomic variations in multiple pregnancies and unusual sonographic features do exist. We have summarized our own experiences and reports from the literature on these pitfalls as follows: (1) discordant fetal sex in monochorionic pregnancies due to sex chromosome abnormalities, genital malformation in 1 fetus, or dizygotic twins forming a monochorionic placenta; (2) separate placental masses in monochorionic pregnancies due to bipartite placenta; (3) false-negative and false-positive λ sign can arise for various reasons, and in partial monochorionic/dichorionic placentas both T and λ sign may co-exist; (4) intrauterine synechia appearing as a thick and echogenic intrauterine septum may lead to erroneous diagnosis of dichorionic twins; and (5) errors in ascertaining amnionicity by the visualization of thin intertwin amniotic membranes and the number of yolk sacs. The ultrasound techniques to reduce inaccuracy in prenatal determination of chorioamnionicity and the use of single nucleotide polymorphisms based on noninvasive prenatal test to determine zygosity are also reviewed.

Midtrimester transvaginal ultrasound cervical length screening for spontaneous preterm birth in diamniotic twin pregnancies according to chorionicity

OBJECTIVE

To compare the mean transvaginal ultrasound (TVU) cervical length (CL) at midtrimester screening for spontaneous preterm birth in asymptomatic monochorionic diamniotic versus dichorionic diamniotic twin pregnancies STUDY DESIGN: This was a multicenter retrospective cohort study. Study subjects were identified at the time of a routine second trimester fetal ultrasound exam at 18 0/7-23 6/7 weeks gestation. We excluded women that received progesterone, pessary, or cerclage. Distribution of CL was determined and normality was examined. Mean of TVU CL were compared between monochorionic diamniotic and dichorionic diamniotic pregnancies. The relationship of TVU CL with gestational age (GA) at delivery and incidence of spontaneous preterm birth (SPTB) at different TVU CL cut offs were assessed. Incidence of short TVU CL, defined as TVU CL ≤30 mm, was also calculated in the two groups.

RESULTS

580 women with diamniotic twin pregnancies underwent TVU CL screening between 18 0/6 and 23 6/7 weeks. 175 (30.2%) were monochorionic diamniotic pregnancies, and 405 (69.8%) were dichorionic pregnancies. The demographic characteristics were similar on both groups. The mean GA at TVU CL was about 20 week in both groups. The mean TVU CL was significantly lower in the monochorionic diamniotic (32.8 ± 10.1) compared to the dichorionic (34.9 ± 8.6) group (MD -2.10 mm, 95% CI -3.91 to -0.29). TVU CL ≤30 mm was 16.6% (29/175) in the monochorionic group, and 11.9% (48/405) in the dichorionic group (aOR 1.48, 95% CI 1.03-2.43). Twins with a monochorionic diamniotic pregnancy had a significantly higher incidence of SPTB (53.1% vs 44.9%; aOR 1.22, 95% CI 1.22-1.79). For any given CL measured between 18 0-7 and 23 6/7 weeks, gestational age at delivery for monochorionic diamniotic pregnancies was about 2 weeks earlier compared to dichorionic pregnancies (MD -2.1 weeks; ANCOVA P < 0.001).

CONCLUSION

Monochorionic diamniotic twin pregnancies had a higher rate of spontaneous preterm birth than dichorionic diamniotic pregnancies. The higher rate of spontaneous preterm delivery in monochorionic pregnancies is associated with lower midtrimester TVU CL when compared to dichorionic pregnancies.

Evaluation of placental vascularization indices in monochorionic diamniotic and dichorionic diamniotic twin pregnancies

OBJECTIVES

We aimed to investigate and compare placental vascularization indices between monochorionic-diamniotic, dichorionic-diamniotic normal twin pregnancies, and normal singular pregnancies. We hypothesized that there is correlation between placental three-dimensional power Doppler vascularization indices and birth weight in case of twin pregnancies, and that normal singular pregnancies have higher placental vascularization indices than normal twin pregnancies.

STUDY DESIGN

Placental three-dimensional power Doppler vascularization indices, such as vascularization index, flow index, and vascularization-flow index were measured in monochorionic-diamniotic (N = 15) and dichorionic-diamniotic (N = 36) normal twin pregnancies, and in normal singular (N = 109) pregnancies. Correlations were analyzed between vascularization indices, and birth weight, APGAR score, umbilical pH, umbilical venous bicarbonate, lactate, and base excess.

RESULTS

Vascularization indices and birth weight were significantly (p < 0.01) higher in normal singular gestations (vascularization index = 10.36, flow index = 46.08, vascularization-flow index = 4.08, average birth weight = 3377 g at 38.2 weeks average gestational age) compared to monochorionic-diamniotic and dichorionic-diamniotic normal twin pregnancies. No significant differences were found in vascularization indices between monochorionic-diamniotic and dichorionic-diamniotic normal twins. There were no significant differences in APGAR score, umbilical pH, umbilical venous bicarbonate, lactate, and base excess between groups examined (p < 0.01). We found strong linear correlations between placental vascularization indices and birth weight in both twin groups.

CONCLUSION

Placental three-dimensional power Doppler vascularization indices seem appropriate for predicting birth weight in monochorionic-diamniotic and dichorionic-diamniotic normal twin pregnancies. Our pilot study revealed reference values for vascularization indices in case of twin pregnancies examined.

Role of ultrasonography in the management of twin gestation

Twins represent 1%-2% of all pregnancies, yet continue to account for a disproportionate share of neonatal adverse events including neonatal intensive care admission, morbidity, and mortality. Ultrasonography is central to the proper diagnosis of the type of twinning. Ideally, ultrasonography is performed before 14 weeks of gestation to determine chorionicity and amnionicity. Correct identification of the chorionicity in a twin pregnancy facilitates proper counseling and management of the gestation, including ultrasonography follow-up. Herein, the different types of twinning are reviewed, together with the implications for ultrasonography monitoring of each specific type of twin gestation.

Risk of spontaneous preterm birth in IVF-conceived twin pregnancies

OBJECTIVE

To compare the mean transvaginal ultrasound (TVU) cervical length (CL) at midtrimester in screening for preterm birth in in vitro (IVF)-conceived twin pregnancies versus spontaneously-conceived twin pregnancies.

METHODS

This was a retrospective cohort study. Potential study subjects were identified at the time of a routine second trimester fetal ultrasound exam at 18 0/7 to 23 6/7-week gestation. All women with twin diamniotic pregnancies screened with a single TVU CL for this trial were included. Mean TVU CLs were compared between IVF-conceived twin pregnancies and spontaneously-conceived twin pregnancies. The relationship of TVU CL with gestational age at delivery was assessed. Incidence of short TVU CL, defined as TVU CL ≤30 mm, was also calculated in the two groups. The primary outcome was the mean of TVU CL. Distribution of CL was determined and normality was examined in both groups Results: A total of 668 women with diamniotic twin pregnancies who underwent TVU CL screening between 18 0/6 and 23 6/7 weeks were included. 158 (23.7%) were IVF-conceived pregnancies, and 510 (76.3%) were spontaneously-conceived pregnancies. No women received progesterone, pessary, or cerclage for preterm birth prevention during pregnancy. The mean TVU CL was significantly lower in the IVF-conceived group (32.2 ± 10.5 mm) compared to the spontaneously-conceived group (34.1 ± 9.1 mm) (mean difference (MD) - 1.90 mm, 95%CI -3.72 to -0.08). The incidence of TVU CL ≤30 mm was 30.4% in the IVF-conceived group and 21.6% in the spontaneously-conceived group (adjusted odds ratio (aOR) 1.59, 95%CI 1.06-2.37). IVF-conceived twins had a significantly higher risk of spontaneous preterm birth <34 weeks (32.9 versus 21.2%; aOR 1.83, 95% confidence interval (CI) 1.23-2.71) and higher rate of delivery due to spontaneous onset of labor (64.5 versus 54.9%; aOR 1.50, 95%CI 1.03-2.17). For any given TVU CL measured between 18 0-7 and 23 6/7 weeks, gestational age at delivery for IVF-conceived twins was earlier by about 1 week on average compared with spontaneously-conceived twins.

CONCLUSIONS

The higher rate of spontaneous preterm birth in IVF-conceived twin pregnancies is predicted by lower midtrimester TVU CL, as well as by the lower gestational age at birth per any given CL in the IVF-conceived compared to the spontaneously-conceived twin pregnancies.

Adverse pregnancy, birth, and infant outcomes in twins: effects of maternal fertility status and infant gender combinations; the Massachusetts Outcomes Study of Assisted Reproductive Technology

BACKGROUND

It is unknown whether the risk of adverse outcomes in twin pregnancies among subfertile women, conceived with and without in vitro fertilization, differs from those conceived spontaneously.

OBJECTIVE

We sought to evaluate the effects of fertility status on adverse perinatal outcomes in twin pregnancies on a population basis.

STUDY DESIGN

All twin live births of ≥22 weeks' gestation and ≥350 g birthweight to Massachusetts resident women in 2004 through 2010 were linked to hospital discharge records, vital records, and in vitro fertilization cycles. Women were categorized by their fertility status as in vitro fertilization, subfertile, or fertile, and by twin pair genders (all, like, unlike). Women whose births linked to in vitro fertilization cycles were classified as in vitro fertilization; those with indicators of subfertility but without in vitro fertilization treatment were classified as subfertile; all others were classified as fertile. Risks of 6 adverse pregnancy outcomes (gestational diabetes, pregnancy hypertension, uterine bleeding, placental complications [placenta abruptio, placenta previa, and vasa previa], prenatal hospitalizations, and primary cesarean) and 9 adverse infant outcomes (very low birthweight, low birthweight, small-for-gestation birthweight, large-for-gestation birthweight, very preterm [<32 weeks], preterm, birth defects, neonatal death, and infant death) were modeled by fertility status with the fertile group as reference, using multivariate log binomial regression and reported as adjusted relative risk ratios and 95% confidence intervals.

RESULTS

The study population included 10,352 women with twin pregnancies (6090 fertile, 724 subfertile, and 3538 in vitro fertilization). Among all twins, the risks for all 6 adverse pregnancy outcomes were significantly increased for the subfertile and in vitro fertilization groups, with highest risks for uterine bleeding (adjusted relative risk ratios, 1.92 and 2.58, respectively) and placental complications (adjusted relative risk ratios, 2.07 and 1.83, respectively). Among all twins, the risks for those born to subfertile women were significantly increased for very preterm birth and neonatal and infant death (adjusted relative risk ratios, 1.36, 1.89, and 1.87, respectively). Risks were significantly increased among in vitro fertilization twins for very preterm birth, preterm birth, and birth defects (adjusted relative risk ratios, 1.28, 1.07, and 1.26, respectively).

CONCLUSION

Risks of all maternal and most infant adverse outcomes were increased for subfertile and in vitro fertilization twins. Among all twins, the highest risks were for uterine bleeding and placental complications for the subfertile and in vitro fertilization groups, and neonatal and infant death in the subfertile group. These findings provide further evidence supporting single embryo transfer and more cautious use of ovulation induction.

Interventions for treating hyperemesis gravidarum: a Cochrane systematic review and meta-analysis

INTRODUCTION

While nausea and vomiting in early pregnancy are very common, affecting approximately 80% of the pregnancies, hyperemesis gravidarum is a severe form affecting 0.3-1.0% of the pregnancies. Although hyperemesis gravidarum is rarely a source of mortality, it is a significant source of morbidity. It is one of the most common indications for hospitalization in pregnancy. Beyond the maternal and fetal consequences of malnutrition, the severity of hyperemesis symptoms causes a major psychosocial burden leading to depression, anxiety, and even pregnancy termination. The aim of this meta-analysis was to examine all randomized controlled trials of interventions specifically for hyperemesis gravidarum and evaluate them based on both subjective and objective measures of efficacy, maternal and fetal/neonatal safety, and economic costs.

MATERIAL AND METHODS

Randomized controlled trials were identified by searching electronic databases. We included all randomized controlled trials for the treatment of hyperemesis gravidarum. The primary outcome was intervention efficacy as defined by severity, reduction, or cessation in nausea/vomiting; number of episodes of emesis; and days of hospital admission. Secondary outcomes included other measures of intervention efficacy, adverse maternal/fetal/neonatal outcomes, quality of life measures, and economic costs.

RESULTS

Twenty-five trials (2052 women) met the inclusion criteria but the majority of 18 different comparisons described in the review include data from single studies with small numbers of participants. Selected comparisons reported below: No primary outcome data were available when acupuncture was compared with placebo. There was insufficient evidence to identify clear differences between acupuncture and metoclopramide in a study with 81 participants regarding reduction/cessation in nausea or vomiting (risk ratio (RR) 1.40, 95% CI 0.79-2.49 and RR 1.51, 95% CI 0.92-2.48, respectively). Midwife-led outpatient care was associated with fewer hours of hospital admission than routine inpatient admission (mean difference (MD) - 33.20, 95% CI -46.91 to -19.49) with no difference in pregnancy-unique quantification of emesis and nausea (PUQE) score, decision to terminate the pregnancy, miscarriage, small-for-gestational age infants, or time off work when compared with routine care. Women taking vitamin B6 had a slightly longer hospital stay compared with placebo (MD 0.80 days, 95% CI 0.08-1.52). There was insufficient evidence to demonstrate a difference in other outcomes including mean number of episodes of emesis (MD 0.50, 95% CI -0.40-1.40) or side effects. A comparison between metoclopramide and ondansetron identified no clear difference in the severity of nausea or vomiting (MD 1.70, 95% CI -0.15-3.55, and MD -0.10, 95% CI -1.63-1.43; one study, 83 women, respectively). However, more women taking metoclopramide complained of drowsiness and dry mouth (RR 2.40, 95% CI 1.23-4.69, and RR 2.38, 95% CI 1.10-5.11, respectively). There were no clear differences between groups for other side effects. In a single study with 146 participants comparing metoclopramide with promethazine, more women taking promethazine reported drowsiness, dizziness, and dystonia (risk ratio (RR) 0.70, 95% CI 0.56-0.87, RR 0.48, 95% CI 0.34-0.69, and RR 0.31, 95% CI 0.11-0.90, respectively). There were no clear differences between groups for other important outcomes including quality of life and other side effects. In a single trial with 30 women, those receiving ondansetron had no difference in duration of hospital admission compared to those receiving promethazine (mean difference (MD) 0.00, 95% CI -1.39-1.39), although there was increased sedation with promethazine (RR 0.06, 95% CI 0.00-0.94). Regarding corticosteroids, in a study with 110 participants there was no difference in days of hospital admission compared to placebo (MD -0.30, 95% CI -0.70-0.10), but there was a decreased readmission rate (RR 0.69, 95% CI 0.50-0.94; 4 studies, 269 women). For hydrocortisone compared with metoclopramide, no data were available for primary outcomes and there was no difference in the readmission rate (RR 0.08, 95% CI 0.00-1.28; one study, 40 women). In a study with 80 women, compared to promethazine, those receiving prednisolone had increased nausea at 48 h (RR 2.00, 95% CI 1.08-3.72), but not at 17 days (RR 0.81, 95% CI 0.58-1.15). There was no clear difference in the number of episodes of emesis or subjective improvement in nausea/vomiting.

CONCLUSIONS

While there were a wide range of interventions studied, both pharmaceutical and otherwise, there were a limited number of placebo controlled trials. In comparing the efficacy of the commonly used antiemetics, metoclopramide, ondansetron, and promethazine, the results of this review do not support the clear superiority of one over the other in symptomatic relief. Other factors such as side effect profile medication safety and healthcare costs should also be considered when selecting an intervention.