Ultrasound in twin pregnancies

Clinical practice guidelines for the antenatal management of dichorionic diamniotic twin pregnancies: a systematic review

OBJECTIVE

This review aimed to identify guidelines with recommendations applicable to the antenatal management of dichorionic diamniotic twin pregnancies within high-income countries, appraise their methodological quality, and discuss the similarities and variability across guidelines.

METHOD

A systematic literature review of electronic databases was performed. Manual searches of guideline repositories and websites of professional organisations were performed to identify additional guidelines. The protocol for this systematic review was registered on PROSPERO (CRD42021248586, 25 June 2021). AGREE II and AGREE-REX tools were applied to assess the quality of eligible guidelines. A narrative and thematic synthesis described and compared the guidelines and their recommendations.

RESULTS

Twenty-four guidelines were included, from which 483 recommendations were identified across 4 international organisations and 12 countries. Guidelines addressed eight themes and recommendations were classified accordingly: chorionicity and dating (103 recommendations), fetal growth (105 recommendations), termination of pregnancy (12 recommendations), fetal death (13 recommendations), fetal anomalies (65 recommendations), antenatal care (65 recommendations), preterm labour (56 recommendations) and birth (54 recommendations). Guidelines showed significant variability in recommendations, with conflicting recommendations regarding non-invasive preterm testing, definitions surrounding selective fetal growth restriction, screening for preterm labour and the timing of birth. Guidelines lacked a focus on standard antenatal management of DCDA twins, management of discordant fetal anomaly and single fetal demise.

CONCLUSIONS

Specific guidance for dichorionic diamniotic twins is overall indistinct and access to guidance regarding the antenatal management of these pregnancies is currently difficult. Management of discordant fetal anomaly or single fetal demise needs greater consideration.

Doppler Ultrasound of the Umbilical Artery: Clinical Application

OBJECTIVE

 To provide a survey of relevant literature on umbilical artery Doppler ultrasound use in clinical practice, technical considerations and limitations, and future perspectives.

METHODS

 Literature searches were conducted in PubMed and Medline, restricted to articles written in English. Additionally, the references of all analyzed studies were searched to obtain necessary information.

RESULTS

 The use of this technique as a routine surveillance method is only recommended for high-risk pregnancies with impaired placentation. Meta-analyses of randomized trials have established that obstetric management guided by umbilical artery Doppler findings can improve perinatal mortality and morbidity. The values of the indices of Umbilical artery Doppler decrease with advancing gestational age; however, a lack of consensus on reference ranges prevails.

CONCLUSION

 Important clinical decisions are based on the information obtained with umbilical artery Doppler ultrasound. Future efforts in research are imperative to overcome the current limitations of the technique.

Should twin-specific growth charts be used to assess fetal growth in twin pregnancies?

One of the hallmarks of twin pregnancies is the slower rate of fetal growth when compared with singleton pregnancies during the third trimester. The mechanisms underlying this phenomenon and whether it represents pathology or benign physiological adaptation are currently unclear. One important implication of these questions relates to the type growth charts that should be used by care providers to monitor growth of twin fetuses. If the slower growth represents pathology (ie, intrauterine growth restriction caused uteroplacental insufficiency), it would be preferable to use a singleton growth chart to identify a small twin fetus that is at risk for perinatal mortality and morbidity. If, however, the relative smallness of twins is the result of benign adaptive mechanisms, it is likely preferable to use a twin-based charts to avoid overdiagnosis of intrauterine growth restriction in twin pregnancies. In the current review, we addressed this question by describing the differences in fetal growth between twin and singleton pregnancies, reviewing the current knowledge regarding the mechanisms responsible for slower fetal growth in twins, summarizing available empirical evidence on the diagnostic accuracy of the 2 types of charts for intrauterine growth restriction in twin pregnancies, and addressing the question of whether uncomplicated dichorionic twins are at an increased risk for fetal death when compared with singleton fetuses. We identified a growing body of evidence that shows that the use of twin charts can reduce the proportion of twin fetuses identified with suspected intrauterine growth restriction by up to 8-fold and can lead to a diagnosis of intrauterine growth restriction that is more strongly associated with adverse perinatal outcomes and hypertensive disorders than a diagnosis of intrauterine growth restriction based on a singleton-based chart without compromising the detection of twin fetuses at risk for adverse outcomes caused by uteroplacental insufficiency. We further found that small for gestational age twins are less likely to experience adverse perinatal outcomes or to have evidence of uteroplacental insufficiency than small for gestational age singletons and that recent data question the longstanding view that uncomplicated dichorionic twins are at an increased risk for fetal death caused by placental insufficiency. Overall, it seems that, based on existing evidence, the of use twin charts is reasonable and may be preferred over the use of singleton charts when monitoring the growth of twin fetuses. Still, it is important to note that the available data have considerable limitations and are primarily derived from observational studies. Therefore, adequately-powered trials are likely needed to confirm the benefit of twin charts before their use is adopted by professional societies.

Controversies in the management of twin pregnancy

Despite many advances in antenatal care, twin pregnancies still experience more adverse outcomes, in particular perinatal morbidity and mortality. They also pose a multitude of challenges and controversies, as outlined in this Review. Moreover, they are less likely to be included in clinical trials. Many issues on classification and management remain under debate. Efforts at standardizing diagnostic criteria, monitoring protocols, management and outcome reporting are likely to reduce their perinatal risks. The top 10 most important research uncertainties related to multiple pregnancies have been identified by both clinicians and patients. More robust research in the form of randomized trials and large well-conducted prospective cohort studies is needed to address these controversies. © 2020 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Ultrasound for diagnosis of birth weight discordance in twin pregnancies

BACKGROUND

There is a need to standardize monitoring in obstetric research of twin pregnancies. Identification of birth weight discordance (BWD), defined as a difference in the birth weights of twins, is a well-documented phenomenon in twin pregnancies. Ultrasound for the diagnosis of BWD informs complex decision making including whether to intervene medically (via laser photo coagulation) or deliver the twins to avoid fetal morbidities or even death. The question is, how accurate is this measurement?

OBJECTIVES

To determine the diagnostic accuracy (sensitivity and specificity) of ultrasound estimated fetal weight discordance (EFWD) of 20% and 25% using different estimated biometric ultrasound measurements compared with the actual BWD as the reference standard in twin pregnancies.

SEARCH METHODS

The search for this review was performed on 15 March 2019. We searched CENTRAL, MEDLINE (Ovid), Embase (Ovid), seven other databases, conference proceedings, reference lists and contacted experts. There were no language or date restrictions applied to the electronic searches, and no methodological filters to maximize sensitivity.

SELECTION CRITERIA

We selected cohort-type studies with delayed verification that evaluated the accuracy of biometric measurements at ultrasound scanning of twin pregnancies that had been proposed for the diagnosis of estimated BWD, compared to BWD measurements after birth as a reference standard. In addition, we only selected studies that considered twin pregnancies and applied a reference standard for EFWD for the target condition of BWD.

DATA COLLECTION AND ANALYSIS

We screened all titles generated by electronic database searches. Two review authors independently assessed the abstracts of all potentially relevant studies. We assessed the identified full papers for eligibility, and extracted data to create 2 × 2 tables. Two review authors independently performed quality assessment using the QUADAS-2 tool. We excluded studies that did not report data in sufficient detail to construct 2 × 2 tables, and where this information was not available from the primary investigators. We assessed the certainty of the evidence using the GRADE approach.

MAIN RESULTS

We included 39 eligible studies with a median study sample size of 140. In terms of risk of bias, there were many unclear statements regarding patient selection, index test and use of proper reference standard. Twenty-one studies (53%) were of methodological concern due to flow and timing. In terms of applicability, most studies were of low concern. Ultrasound for diagnosis of BWD in twin pregnancies at 20% cut-off Twenty-two studies provided data for a BWD of 20% and the summary estimate of sensitivity was 0.51 (95% CI 0.42 to 0.60), and the summary estimate of specificity was 0.91 (95% CI 0.89 to 0.93) (8005 twin pregnancies; very low-certainty evidence). Ultrasound for diagnosis of BWD in twin pregnancies at 25% cut-off Eighteen studies provided data using a BWD discordance of 25%. The summary estimate of sensitivity was 0.46 (95% CI 0.26 to 0.66), and the summary estimate of specificity was 0.93 (95% CI 0.89 to 0.96) (6471 twin pregnancies; very low-certainty evidence). Subgroup analyses were possible for both BWD of 20% and 25%. The diagnostic accuracy did not differ substantially between estimation by abdominal circumference and femur length but femur length had a trend towards higher sensitivity and specificity. Subgroup analyses were not possible by sex of twins, chorionicity or gestational age due to insufficient data.

AUTHORS' CONCLUSIONS

Very low-certainty evidence suggests that EFWD identified by ultrasound has low sensitivity but good specificity in detecting BWD in twin pregnancies. There is uncertain diagnostic value of EFWD; this review suggests there is insufficient evidence to support this index as the sole measure for clinical decision making to evaluate the prognosis of twins with growth discordance. The diagnostic accuracy of other measures including amniotic fluid index and umbilical artery Doppler resistive indices in combination with ultrasound for clinical intervention requires evaluation. Future well-designed studies could also evaluate the impact of chorionicity, sex and gestational age in the diagnostic accuracy of ultrasound for EFWD.

Cervical Assessment for Predicting Preterm Birth-Cervical Length and Beyond

Preterm birth is considered one of the main etiologies of neonatal death, as well as short- and long-term disability worldwide. A number of pathophysiological processes take place in the final unifying factor of cervical modifications that leads to preterm birth. In women at high risk for preterm birth, cervical assessment is commonly used for prediction and further risk stratification. This review outlines the rationale for cervical length screening for preterm birth prediction in different clinical settings within existing and evolving new technologies to assess cervical remodeling.

Clinical Practice Guidelines for Prenatal Aneuploidy Screening and Diagnostic Testing from Korean Society of Maternal-Fetal Medicine: (2) Invasive Diagnostic Testing for Fetal Chromosomal Abnormalities

The Korean Society of Maternal Fetal Medicine proposed the first Korean guideline on prenatal aneuploidy screening and diagnostic testing, in April 2019. The clinical practice guideline (CPG) was developed for Korean women using an adaptation process based on good-quality practice guidelines, previously developed in other countries, on prenatal screening and invasive diagnostic testing for fetal chromosome abnormalities. We reviewed current guidelines and developed a Korean CPG on invasive diagnostic testing for fetal chromosome abnormalities according to the adaptation process. Recommendations for selected 11 key questions are: 1) Considering the increased risk of fetal loss in invasive prenatal diagnostic testing for fetal genetic disorders, it is not recommended for all pregnant women aged over 35 years. 2) Because early amniocentesis performed before 14 weeks of pregnancy increases the risk of fetal loss and malformation, chorionic villus sampling (CVS) is recommended for pregnant women who will undergo invasive prenatal diagnostic testing for fetal genetic disorders in the first trimester of pregnancy. However, CVS before 9 weeks of pregnancy also increases the risk of fetal loss and deformity. Thus, CVS is recommended after 9 weeks of pregnancy. 3) Amniocentesis is recommended to distinguish true fetal mosaicism from confined placental mosaicism. 4) Anti-immunoglobulin should be administered within 72 hours after the invasive diagnostic testing. 5) Since there is a high risk of vertical transmission, an invasive prenatal diagnostic testing is recommended according to the clinician's discretion with consideration of the condition of the pregnant woman. 6) The use of antibiotics is not recommended before or after an invasive diagnostic testing. 7) The chromosomal microarray test as an alternative to the conventional cytogenetic test is not recommended for all pregnant women who will undergo an invasive diagnostic testing. 8) Amniocentesis before 14 weeks of gestation is not recommended because it increases the risk of fetal loss and malformation. 9) CVS before 9 weeks of gestation is not recommended because it increases the risk of fetal loss and malformation. 10) Although the risk of fetal loss associated with invasive prenatal diagnostic testing (amniocentesis and CVS) may vary based on the proficiency of the operator, the risk of fetal loss due to invasive prenatal diagnostic testing is higher in twin pregnancies than in singleton pregnancies. 11) When a monochorionic twin is identified in early pregnancy and the growth and structure of both fetuses are consistent, an invasive prenatal diagnostic testing can be performed on one fetus alone. However, an invasive prenatal diagnostic testing is recommended for each fetus in cases of pregnancy conceived via in vitro fertilization, or in cases in which the growth of both fetuses differs, or in those in which at least one fetus has a structural abnormality. The guidelines were established and approved by the Korean Academy of Medical Sciences. This guideline is revised and presented every 5 years.

Early ultrasound diagnosis of conjoined twins at eight weeks of pregnancy: A case report

BACKGROUND

Conjoined twins are a rare occurrence, and the majority of these malformations are detected during second trimester screening.

CASE SUMMARY

Herein we report a case of conjoined twins, which was diagnosed by ultrasound at 8 wk gestation and was normal at 7 wk gestation. The two fetuses shared one heart and were diagnosed as thoracopagus twins. This is the first report of conjoined twins diagnosed at 8 wk gestation. The pregnancy was terminated electively at 9 wk gestation. Because some congenital malformations can be diagnosed earlier, a prenatal ultrasound examination at an early gestational stage cannot be dismissed.

CONCLUSION

This case demonstrates that a 7-8 wk gestation might be the earliest period when conjoined twins can be diagnosed by ultrasound.

No. 363-Investigation and Management of Non-immune Fetal Hydrops

OBJECTIVE

To describe the current investigation and management of non-immune fetal hydrops with a focus on treatable or recurring etiologies.

OUTCOMES

To provide better counselling and management in cases of prenatally diagnosed non-immune hydrops.

EVIDENCE

Published literature was retrieved through searches of PubMed or MEDLINE, CINAHL, and The Cochrane Library in 2017 using key words (non-immune hydrops fetalis, fetal hydrops, fetal therapy, fetal metabolism). Results were restricted to systematic reviews, randomized controlled trials/controlled clinical trials, observational studies, and significant case reports. Additional publications were identified from the bibliographies of these articles. There were no date or language restrictions. Searches were updated on a regular basis and incorporated in the guideline to September 2017. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology-related agencies, clinicalpractice guideline collections, clinical trial registries, and national and international medical specialty societies.

BENEFITS, HARMS, AND COSTS

These guidelines educate readers about the causes of non-immune fetal hydrops and its prenatal counselling and management. It also provides a standardized approach to non-immune fetal hydrops, emphasizing the search for prenatally treatable conditions and recurrent genetic etiologies.

VALUES

The quality of evidence in this document was rated using the criteria described in the Report of the Canadian Task Force on Preventive Health Care.

RECOMMENDATIONS

Two cases of atypical twinning: Phenotypically discordant monozygotic and conjoined twins

Atypical twinning highlights that complex mechanisms responsible for twinning are not fully understood and may give further insight into the mechanisms involved. To assume that phenotypic difference is the result of dizygotic twinning would be erroneous and could have significant implications in the care and counseling provided to these patients.

The value of ultrasound in predicting isolated inter-twin discordance and adverse perinatal outcomes

PURPOSE

To investigate the value of ultrasound approaching delivery to predict isolated inter-twin discordance and adverse perinatal outcomes.

METHODS

We retrospectively included twin pregnancies with sonography approaching delivery in ten maternal-foetal medicine centres in China from 2013 to 2014. Estimated foetal weight (EFW) and inter-twin EFW disparity (EFWD) were calculated based on biometry parameters. Percentage errors between EFW and actual birthweight or between EFWD and actual inter-twin disparity were calculated. ROC curves and multiple logistic regression were applied to evaluate the ability of EFWD to predict inter-twin disparity ≥ 25%, stillbirth, asphyxia and admission to a neonatal intensive unit (NICU). Chorionicity-stratified analysis was further performed.

RESULTS

Two hundred sixty-six monochorionic and 760 dichorionic twin pregnancies were analysed. The percentage errors in foetal weight estimations were 7-13%, whereas percentage errors in the estimation of inter-twin disparity were nearly 100%. Among eight formulas, Hadlock1 performed best, with a detectable rate of 65% and a false positive rate of 5% when predicting inter-twin disparity ≥ 25%. EFWD ≥ 22% was strongly associated with stillbirth (OR = 4.17, 95% CI 1.40-12.40) and NICU admission (OR = 3.48, 95% CI 2.03-5.97) after adjustment for gestational age, parity and abnormal umbilical systolic/diastolic ratio. Ultrasound had better predictive ability in monochorionic twins.

CONCLUSION

The predictive value of ultrasound for isolated inter-twin discordance and adverse perinatal outcomes was limited, which was possibly due to the magnifying of systematic errors in the disparity estimation compared with weight estimation. Despite this, abnormal biometry was an independent contributor for the poor prognosis of neonates.

Prognosis of the co-twin following spontaneous single intrauterine fetal death in twin pregnancies: a systematic review and meta-analysis

BACKGROUND

Single intrauterine fetal death affects approximately 6% of twin pregnancies and can have serious sequelae for the surviving co-twin.

OBJECTIVES

Determine the prognosis of the surviving co-twin following spontaneous single intrauterine fetal death to aid counselling patients and highlight future research areas.

SEARCH STRATEGY

Medline, Embase, Web of Science, and Cochrane Library, from 1980 to June 2017.

SELECTION CRITERIA

Studies of five or more cases of spontaneous single intrauterine fetal death after 14 weeks gestation, in diamniotic twin pregnancies.

DATA COLLECTION AND ANALYSIS

Summary event rates were calculated and stratified by chorionicity. Monochorionic and dichorionic twins, and sub-groups, were compared by odds ratios.

MAIN RESULTS

In monochorionic twins, when single intrauterine fetal death occurred at less than 28 weeks' gestation, this significantly increased the rate of co-twin intrauterine fetal death [odds ratio (OR) 2.31, 95% confidence interval (CI) 1.02-5.25, I²  = 0.0%, 12 studies, 184 pregnancies] and neonatal death (OR 2.84, 95% CI 1.18-6.77, I²  = 0.0%, 10 studies, 117 pregnancies) compared with when the single intrauterine fetal death occurred at more than 28 weeks' gestation. Neonatal death in monochorionic twins was significantly higher if the pregnancy was complicated by fetal growth restriction (OR 4.83, 95% CI 1.14-20.47, I²  = 0.0%, six studies, 60 pregnancies) or preterm birth (OR 4.95, 95% CI 1.71-14.30, I²  = 0.0%, 11 studies, 124 pregnancies). Abnormal antenatal brain imaging was reported in 20.0% (95% CI 12.8-31.1, I²  = 21.9%, six studies, 116 pregnancies) of surviving monochorionic co-twins. The studies included in the meta-analysis demonstrated small study effects and possible selection bias.

CONCLUSIONS

Preterm birth was the commonest adverse outcome affecting 58.5 and 53.7% of monochorionic and dichorionic twin pregnancies. Outcomes regarding brain imaging and neurodevelopmental comorbidity are an important area for future research, but meta-analysis may be limited due to different methods of assessment.

TWEETABLE ABSTRACT

Preterm birth is the highest risk in single co-twin death. Abnormal antenatal brain imaging was found in 1/5 surviving MC twins.

Ultrasound surveillance in twin pregnancy: An update for practitioners

Ultrasound has revolutionised the management of multiple pregnancies and their complications. Increasing frequency of twin pregnancies mandates familiarity of all clinicians with the relevant pathologies and evidence-based surveillance and management protocols for their care. In this review, we summarise the latest evidence relating to ultrasound surveillance of twin pregnancies including first trimester assessment and screening, growth surveillance and the detection and management of the complications of monochorionic pregnancies including twin-to-twin-transfusion syndrome, selective fetal growth restriction, twin reversed arterial perfusion sequence and conjoined twinning.

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.

N° 363 - Évaluation et prise en charge de l'anasarque fœtoplacentaire non immune

OBJECTIF

Décrire les méthodes actuelles d'évaluation et de prise en charge de l'anasarque fœtoplacentaire non immune en mettant l'accent sur les étiologies traitables ou récurrentes. RéSULTATS: Offrir de meilleurs services de conseil et de prise en charge en cas d'anasarque fœtoplacentaire non immune diagnostiquée en période prénatale. DONNéES: La littérature publiée a été récupérée au moyen de recherches menées dans PubMed, MEDLINE, CINAHL, et la Bibliothèque Cochrane en 2017 à l'aide de mots-clés (« non-immune hydrops fetalis », « fetal hydrops », « fetal therapy », « fetal metabolism »). Les articles retenus portaient sur des revues systématiques, des essais cliniques contrôlés, randomisés ou non, des études observationnelles et des études de cas importantes. D'autres publications ont été repérées dans les bibliographies de ces articles. Aucune restriction de date ou de langue n'a été employée. Les recherches ont été mis à jour régulièrement, et les résultats ont été incorporés à la directive clinique jusqu'en septembre 2017. Nous avons également tenu compte de la littérature grise (non publiée) trouvée sur les sites Web d'organismes d'évaluation des technologies de la santé et d'autres organismes liés aux technologies de la santé, dans des collections de directives cliniques et des registres d'essais cliniques, et obtenue auprès d'associations nationales et internationales de médecins spécialistes. AVANTAGES, INCONVéNIENTS ET COûTS: La présente directive clinique renseigne les lecteurs sur les causes de l'anasarque fœtoplacentaire non immune ainsi que sur son évaluation et sa prise en charge. Elle propose également une approche standardisée d'évaluation et de prise en charge, et met l'accent sur la recherche des conditions traitables en période prénatale et des étiologies génétiques récurrentes.

VALEURS

La qualité des données probantes a été évaluée en fonction des critères décrits dans le rapport du Groupe d'étude canadien sur les soins de santé préventifs. RECOMMANDATIONS.

ACR Appropriateness Criteria® Multiple Gestations

Women with twin or higher-order pregnancies will typically have more ultrasound examinations than women with a singleton pregnancy. Most women will have at minimum a first trimester scan, a nuchal translucency evaluation scan, fetal anatomy scan at 18 to 22 weeks, and one or more scans in the third trimester to evaluate growth. Multiple gestations are at higher risk for preterm delivery, congenital anomalies, fetal growth restriction, placenta previa, vasa previa, and velamentous cord insertion. Chorionicity and amnionicity should be determined as early as possible when a twin pregnancy is identified to permit triage of the monochorionic group into a closer surveillance model. Screening for congenital heart disease is warranted in monochorionic twins because they have an increased rate of congenital cardiac anomalies. In addition, monochorionic twins have a higher risk of developing cardiac abnormalities in later gestation related to right ventricular outflow obstruction, in particular the subgroups with twin-twin transfusion syndrome or selective intrauterine growth restriction. Monochorionic twins have unique complications including twin-to-twin transfusion syndrome, twin embolization syndrome, and acardius, or twin-reversed arterial perfusion sequence. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Clinical guidelines for prevention and management of preterm birth: a systematic review

BACKGROUND

Clinical practice guidelines (CPG) endorse multiple strategies to prevent or manage preterm birth (PTB).

OBJECTIVES

To summarise CPG recommendations for PTB and identify areas of international consensus.

SEARCH STRATEGY

In May 2017 we searched for all CPG relevant to PTB without language restrictions.

SELECTION CRITERIA

CPG were eligible if the following criteria were met: (1) the guideline was published or current from June 2013; (2) the guideline recommended practices for the prevention or management of PTB relevant to our prespecified clinical questions for screening, medications or surgery and other interventions; (3) publications on methods of guideline development for eligible CPG were included to enable quality assessment.

DATA COLLECTION AND ANALYSIS

Two authors classified CPG recommendations relevant to prespecified clinical questions. When more than 70% of CPGs reporting on a topic recommended or rejected an intervention, we regarded this as consensus. We summarised recommendations in tables.

MAIN RESULTS

We identified 49 guidelines from 16 guideline developers. We found consensus for several clinical practices: cervical length screening for high-risk women; short-term tocolysis; steroids for fetal lung maturation; and magnesium sulphate for fetal neuroprotection. We found discrepant recommendations for progesterone and fibronectin. No guideline identified an effective strategy for women with multiple pregnancy.

CONCLUSIONS

We identified interventions for which there is an international consensus on benefit for PTB. Systematic reviews of CPG using standardised methodology will help avoid duplication and target scarce resources for guideline developers globally.

TWEETABLE ABSTRACT

International clinical guidelines agree on the benefits and harmful effects of several important interventions to prevent preterm birth.

Examining the provisional guidelines for weight gain in twin pregnancies: a retrospective cohort study

BACKGROUND

Weight gain during pregnancy has an important impact on maternal and neonatal health. Unlike the Institute of Medicine (IOM) recommendations for weight gain in singleton pregnancies, those for twin gestations are termed "provisional", as they are based on limited data. The objectives of this study were to determine the neonatal and maternal outcomes associated with gaining weight below, within and above the IOM provisional guidelines on gestational weight gain in twin pregnancies, and additionally, to explore ranges of gestational weight gain among women who delivered twins at the recommended gestational age and birth weight, and those who did not.

METHODS

A retrospective cohort study of women who gave birth to twins at ≥20 weeks gestation, with a birth weight ≥ 500 g was conducted in Nova Scotia, Canada (2003-2014). Our primary outcome of interest was small for gestational age (<10th percentile). In order to account for gestational age at delivery, weekly rates of 2nd and 3rd trimester weight gain were used to categorize women as gaining below, within, or above guidelines. We performed traditional regression analyses for maternal outcomes, and to account for the correlated nature of the neonatal outcomes in twins, we used generalized estimating equations (GEE).

RESULTS

A total of 1482 twins and 741 mothers were included, of whom 27%, 43%, and 30% gained below, within, and above guidelines, respectively. The incidence of small for gestational age in these three groups was 30%, 21%, and 20%, respectively, and relative to gaining within guidelines, the adjusted odds ratios were 1.44 (95% CI 1.01-2.06) for gaining below and 0.92 (95% CI 0.62-1.36) for gaining above. The gestational weight gain in women who delivered twins at 37-42 weeks with average birth weight ≥ 2500 g and those who delivered twins outside of the recommend ranges were comparable to each other and the IOM recommendations.

CONCLUSIONS

While gestational weight gain below guidelines for twins was associated with some adverse neonatal outcomes, additional research exploring alternate ranges of gestational weight gain in twin pregnancies is warranted, in order to optimize neonatal and maternal outcomes.

Optimal threshold for birth weight discordance: Does knowledge of chorionicity matter?

OBJECTIVE

To establish the optimal threshold of birth weight discordance (BWD) for prediction of stillbirth, perinatal mortality and morbidity in twins born in British Columbia with or without chorionicity information.

STUDY DESIGN

This is a retrospective population-based cohort study of twins born in British Columbia from 2000 to 2010. Data from one hospital was used to adjust for chorionicity. Multivariate generalized estimating equation and receiver operating characteristic curve analyses were performed to evaluate the predictability of BWD in comparison with other fetal anthropometric measurements. Positive likelihood ratio is used to estimate test accuracy. Survival analysis was conducted to take gestational age and other confounders into account.

RESULTS

We analyzed two cohorts, with (pairs=1493) and without (pairs=6328) chorionicity information, of which 1.5% experienced stillbirth, 2.9% suffered perinatal mortality and 22.6% identified with perinatal morbidities. BWD was a significant predictor of stillbirth. Standard receiver operating characteristic curve analysis and survival analysis suggested that BWD of ⩾30% is the optimal thresholds for stillbirth and perinatal mortality irrespective of chorionicity. However, the P-value for predictive accuracy of BWD was nonsignificant for perinatal morbidity, after adjusting for confounding variables engaging multivariate analysis. Sex discordance can be used as a proxy for chorionicity.

CONCLUSION

BWD is a good predictor for stillbirth. A BWD cutoff limit of 30% and higher has optimal accuracy for detecting perinatal mortality.

The role of routine cervical length screening in selected high- and low-risk women for preterm birth prevention

Preterm birth remains a major cause of neonatal death and short and long-term disability in the US and across the world. The majority of preterm births are spontaneous and cervical length screening is one tool that can be utilized to identify women at increased risk who may be candidates for preventive interventions. The purpose of this document is to review the indications and rationale for CL screening to prevent preterm birth in various clinical scenarios. The Society for Maternal-Fetal Medicine recommends (1) routine transvaginal cervical length screening for women with singleton pregnancy and history of prior spontaneous preterm birth (grade 1A); (2) routine transvaginal cervical length screening not be performed for women with cervical cerclage, multiple gestation, preterm premature rupture of membranes, or placenta previa (grade 2B); (3) practitioners who decide to implement universal cervical length screening follow strict guidelines (grade 2B); (4) sonographers and/or practitioners receive specific training in the acquisition and interpretation of cervical imaging during pregnancy (grade 2B).

Future Directions in the Management of Twin-to-Twin Transfusion Syndrome

Twin-to-twin transfusion syndrome (TTTS) is the major complication of monochorionic (MC) pregnancy. The outcomes of this condition have been significantly improved after the introduction and widespread uptake of fetoscopic laser ablation over the last decade. However, there is still a significant fetal loss rate and morbidity associated with this condition. Improvements in the management of TTTS will require improvements in many areas. They are likely to involve refinements in the prediction of the disease and clarification of the optimum frequency of surveillance and monitoring. Improvements in training for fetoscopic surgery as well as in the technique of fetoscopic laser ablation may lead to better outcomes. New technologies as well as a better understanding of the pathophysiology of TTTS may lead to adjuvant medical therapies that may also improve short- and long-term results.

Dichorionic twin ultrasound surveillance: sonography every 4 weeks significantly underperforms sonography every 2 weeks: results of the Prospective Multicenter ESPRiT Study

OBJECTIVE

A 2-week ultrasound scanning schedule for monochorionic twins is endorsed widely. There is a lack of robust data to inform a schedule for the surveillance of dichorionic gestations. We aimed to determine how ultrasound scanning that is performed at 2- or 4-week intervals (or every 4 weeks before 32 weeks' gestation and every 2 weeks thereafter) may impact the prenatal detection of fetal growth restriction (FGR) and ultimately influence timing of delivery.

STUDY DESIGN

In a consecutive cohort of 789 dichorionic twin pregnancies that were recruited prospectively for the multicenter Evaluation of Sonographic Predictors of Restricted Growth in Twins study, ultrasound determination of fetal growth and interrogation of umbilical and middle cerebral artery Doppler scans were performed every 2 weeks from 24 weeks' gestation until delivery. Complete delivery and perinatal outcome data were recorded for all pregnancies. Where delivery was prompted by FGR, abnormal umbilical artery Doppler examination or poor biophysical profile and in the absence of ruptured membranes, onset of labor, preeclampsia, or antepartum hemorrhage, the delivery was considered "ultrasound-indicated." For ultrasound-indicated deliveries, detection probabilities for FGR/abnormal umbilical artery Doppler scans/poor biophysical were determined according to the interval between examinations, by the suppression if alternate examination data.

RESULTS

Among 789 dichorionic twin pregnancies, 66 pairs (8%) had an "ultrasound indicated" delivery. Detection of FGR was reduced from 88-69%, and detection of abnormal umbilical artery Doppler was reduced from 82-62% when a 4-week ultrasound schedule was simulated. Both of these reductions reached statistical significance. There was a nonsignificant trend toward a reduction in the recording of oligohydramnios with a 4-week interval between examinations.

CONCLUSION

This study suggests that the ultrasound surveillance program of every 2 weeks that is recommended currently for monochorionic twins should be extended to dichorionic gestations.

Discordance in fetal biometry and Doppler are independent predictors of the risk of perinatal loss in twin pregnancies

OBJECTIVE

Impaired fetal growth might be better evaluated in twin pregnancies by assessing the intertwin discordance rather than the individual fetal size. The aim of this study was to investigate the prediction of perinatal loss in twin pregnancy using discordance in fetal biometry and Doppler.

STUDY DESIGN

This was a retrospective cohort study in a tertiary referral center. The estimated fetal weight (EFW), umbilical artery (UA) pulsatility index (PI), middle cerebral artery (MCA) PI, cerebroplacental ratio (CPR), and their discordance recorded at the last ultrasound assessment before delivery or demise of one or both fetuses were converted into centiles or multiples of the median (MoM). The discordance was calculated as the larger value-smaller value/larger value. A logistic regression analysis was performed to identify, and adjust for, potential confounders. The predictive accuracy was assessed using receiver-operating characteristic curve analysis.

RESULTS

The analysis included 620 (464 dichorionic diamniotic and 156 monochorionic diamniotic) twin pregnancies (1240 fetuses). Perinatal loss of one or both fetuses complicated 16 pregnancies (2.6%). The combination of EFW discordance and CPR discordance had the best predictive performance (area under the curve, 0.96; 95% confidence interval, 0.92-1.00) for perinatal mortality. The detection rate, false-positive rate, positive likelihood ratio, and negative likelihood ratio were 87.5%, 6.7%, 13.08, and 0.13, respectively. The EFW centile, EFW below the 10th centile (small for gestational age), UA PI discordance, MCA PI discordance, and MCA PI MoM were significantly associated with the risk of perinatal loss on univariate analysis, but these associations became nonsignificant after adjusting for other confounders (P = .097, P = .090, P = .687, P = .360, and P = .074, respectively). The UA PI MoM, CPR MoM, EFW discordance, and CPR discordance were all independent predictors of the risk of perinatal loss, even after adjusting for potential confounders (P = .022, P = .002, P < .001, and P = .010, respectively).

CONCLUSION

EFW discordance and CPR discordance are independent predictors of the risk of perinatal loss in twin pregnancies. Their combination could identify the majority of twin pregnancies at risk of perinatal loss. These findings highlight the importance of discordance in Doppler indices of fetal hypoxia, as well as fetal size, in assessing the risk of perinatal mortality.

First-trimester Ultrasound and Aneuploidy Screening in Multifetal Pregnancies

First-trimester ultrasound provides valuable information to help optimize the management of multifetal pregnancies. First trimester ultrasound the use of ultrasound and screening for aneuploidy has been well studied in singleton pregnancies. While evidence supporting the use of ultrasound in multiple gestations is well established, aneuploidy screening continues to evolve and its role in the prenatal setting has been less well studied. We review the importance of early first trimester ultrasound in assessing gestational age and chorionicity and early identification of anomalies, and review the various methods and limitations of aneuploidy screening and invasive diagnostic procedures in multiples.

Obstetrical and neonatal outcomes of triplet births - spontaneous versus assisted reproductive technology conception

OBJECTIVE

To determine the average gestational age at birth and to compare obstetrical and neonatal outcomes of triplet births conceived spontaneously versus via assisted reproductive technology (ART).

METHODS

A retrospective chart review of triplet pregnancies that resulted in three live babies was conducted at Mount Sinai Hospital (Toronto, Canada) from January 2000 to June 2013.

RESULTS

A total of 230 women and 690 fetuses were identified. The mean gestational age at birth was 32.0 ± 3.8 weeks. Obstetrical outcomes included preterm premature rupture of the membranes in 29%, preterm labor in 26%, preeclampsia or HELLP syndrome in 19% and gestational diabetes in 10%. The mean birth weight of infants born after 24 weeks was 1655 ± 550 g and the rate of small for gestational age was 28%. The neonatal mortality rate prior to discharge was 7%. Aside from respiratory distress syndrome (30.6 versus 46.6%; p = 0.02), there were no differences in gestational age at birth, obstetrical or neonatal outcomes between spontaneous versus ART triplet conception. Monochorionicity carried a higher risk of small for gestational age, congenital anomalies and neonatal mortality compared to trichorionicity.

CONCLUSION

Rates of preterm birth and related complications remain high in triplet gestation. However, obstetrical and neonatal outcomes were similar for triplets conceived spontaneously versus via ART.

Fetal growth reference ranges in twin pregnancy: analysis of the Southwest Thames Obstetric Research Collaborative (STORK) multiple pregnancy cohort

OBJECTIVE

To generate reference charts for expected fetal growth in dichorionic diamniotic (DCDA) and monochorionic diamniotic (MCDA) twin pregnancies and to compare these with those from singleton pregnancies.

METHODS

This was a retrospective study of biometric measurements from serial ultrasound examinations of twin pregnancies in the second and third trimesters, from 14 weeks' gestation to term, collected by nine hospitals over a 10-year period. The measurements obtained in each fetus at each examination included head circumference (HC), biparietal diameter (BPD), abdominal circumference (AC) and femur length (FL). Multilevel mixed effects statistical models were used to evaluate growth in each biometric variable in relation to gestational age, taking account of the serial examinations and the association between the two fetuses in each pregnancy, with separate models constructed for DCDA and MCDA pregnancies.

RESULTS

The final dataset for analysis included a total of 9866 second- and third-trimester ultrasound examinations in 1802 DCDA and 323 MCDA twin pregnancies, with a median of five (range, 1-14) scans per pregnancy. For each variable, the mean value for DCDA twins was close to the reported value in singletons at 20-30 weeks and showed a decrease relative to singletons beyond 30 weeks. The differences were greater for AC and HC, for which the mean in twins was approximately equivalent to the 30th percentile in singletons at 18 weeks, the 35th percentile at 25 weeks and the 30th percentile at 35 weeks. Fetuses in MCDA twin pregnancies displayed lower mean measurements than did those in DCDA pregnancies throughout the gestational age range considered.

CONCLUSIONS

Ultrasound biometry shows a small but statistically significant reduction in fetal growth in twin pregnancies relative to that in singletons, particularly in the third trimester, with a more marked difference for MCDA than for DCDA pregnancies.

Twin-twin transfusion syndrome: a frequently missed diagnosis with important consequences

OBJECTIVE

To evaluate the incidence and consequences of 'misdiagnosed' cases of twin-twin transfusion syndrome (TTTS).

METHODS

Chorionicity and referral diagnoses were reviewed in pregnant women with monochorionic twin pregnancies complicated by TTTS treated with fetoscopic laser ablation. 'Misdiagnosed' cases, defined as failure to correctly identify chorionicity and/or to diagnose TTTS prior to referral, were compared with cases in whom chorionicity and TTTS were diagnosed correctly. TTTS stage, gestational age at referral, overall survival, fetal and perinatal mortality, gestational age at delivery, operating time and maternal complications were compared.

RESULTS

Failure to identify monochorionicity and/or TTTS was observed in 33% (107/323) of referrals to our center. Compared with cases in whom chorionicity and TTTS were correctly diagnosed, misdiagnosed patients were referred at a more advanced stage of disease (Stage IV TTTS: 16.8% vs 7.9%, P = 0.014) and later in pregnancy (gestational age at laser: 20.9 weeks vs 20.1 weeks, P = 0.018). They also delivered more prematurely (30.3 weeks' gestation vs 31.5 weeks' gestation, P = 0.04) and fetal and neonatal mortality were higher (neonatal death within 7 days: 19.6% vs 6.0%, P < 0.001). When the diagnosis was incorrect, major maternal complications and intensive care unit admissions were increased.

CONCLUSIONS

Poor recognition of chorionicity in the first trimester of pregnancy might lead to inadequate ultrasound follow up (failure to assess every 2 weeks) and patient education. Early accurate recognition of both chorionicity and TTTS, with timely referral to a fetal therapy center, are key to ensuring optimal maternal and fetal outcomes.

Prenatal screening and diagnosis of aneuploidy in multiple pregnancies

Prenatal screening for aneuploidy has changed significantly over the last 30 years, from being age-based to maternal serum and ultrasound based techniques. Multiple pregnancies present particular challenges with regards to screening as serum-based screening techniques are influenced by all feti while ultrasound-based techniques can be fetus specific. Tests currently available tend to not perform as well in multiple compared to singleton pregnancies. Considerations must be given to these variations when discussing and performing screening for aneuploidy in this situation. Prenatal invasive diagnosis techniques in multiple pregnancies bring their own challenges from a technical and counselling point of view, in particular with regards to sampling error, mapping and assignment of results and management of abnormal results. This review addresses these particular challenges and provides information to facilitate care.

Polyhydramnios: Causes, Diagnosis and Therapy

Polyhydramnios is defined as a pathological increase of amniotic fluid volume in pregnancy and is associated with increased perinatal morbidity and mortality. Common causes of polyhydramnios include gestational diabetes, fetal anomalies with disturbed fetal swallowing of amniotic fluid, fetal infections and other, rarer causes. The diagnosis is obtained by ultrasound. The prognosis of polyhydramnios depends on its cause and severity. Typical symptoms of polyhydramnios include maternal dyspnea, preterm labor, premature rupture of membranes (PPROM), abnormal fetal presentation, cord prolapse and postpartum hemorrhage. Due to its common etiology with gestational diabetes, polyhydramnios is often associated with fetal macrosomia. To prevent the above complications, there are two methods of prenatal treatment: amnioreduction and pharmacological treatment with non-steroidal anti-inflammatory drugs (NSAIDs). However, prenatal administration of NSAIDs to reduce amniotic fluid volumes has not been approved in Germany. In addition to conventional management, experimental therapies which would alter fetal diuresis are being considered.

Ultrasound in twins: dichorionic and monochorionic

The objective of this review is to assess the evidence that supports the use of ultrasound in twin pregnancies. Although many of the indications for obstetric ultrasound are the same in both singleton and multiple gestations, there are special considerations as well as unique conditions in twins that require additional imaging studies. The reasons for ultrasound in twins include pregnancy dating, determination of chorionicity, nuchal translucency assessment, anatomical survey, placental evaluation, cervical length assessment, routine fetal growth, and serial surveillance of pregnancies complicated by anomalies, cervical shortening, fetal growth disturbances, and amniotic fluid abnormalities. Twins with monochorionic placentation require heightened scrutiny for monoamnionicity, conjoined twins, twin reversed arterial perfusion (TRAP) syndrome, twin-twin transfusion syndrome, unequal placental sharing with discordant twin growth or selective intrauterine fetal growth restriction (IUGR), twin anemia-polycythemia sequence (TAPS), and single fetal demise. Ultrasound is essential for the detection and management of conditions that can complicate dichorionic and monochorionic twin pregnancies.

Amniotic fluid as a vital sign for fetal wellbeing

Introduction: Amniotic fluid, once thought to merely provide protection and room for necessary movement and growth for the fetus, is now understood to be a highly complex and dynamic system that is studied as a data point to interpret fetal wellbeing. Methods: Assessment of amniotic fluid volume is now routine when performing a sonographic evaluation of fetal status and is an important consideration in the assessment and management of perinatal morbidity and mortality.1,2 In this review, we will cover the dynamics that affect amniotic fluid volume, review methods for measurement and quantification of volume, review definitions for normative data as related to neonatal outcomes, and provide evidence based guidance on the workup and management options for oligoydramnios and polyhydramnios in singleton and twin pregnancies. Conclusions: When abnormalities of fluid exist, appropriate workup to uncover the underlying etiology should be initiated as adverse fetal outcomes are sometimes associated with these variations from normalcy.

Active management of selective intrauterine growth restriction with abnormal Doppler in monochorionic diamniotic twin pregnancies diagnosed in the second trimester of pregnancy

OBJECTIVE

This study aims to compare outcomes of active management of monochorionic diamniotic twin pregnancies complicated with severe intrauterine growth restriction (IUGR) of one twin before 24 weeks with continuous or intermittent absent or reversed end-diastolic flow (AREDF) in the umbilical artery, with or without twin-to-twin transfusion syndrome (TTTS).

METHOD

This study is a retrospective comparison of 45 consecutive cases of severe selective IUGR (s-IUGR) defined as an estimated fetal weight at or below the fifth centile with a >25% weight discordance and AREDF in the umbilical artery before 24 weeks and 166 consecutive cases of TTTS stage III, with AREDF in the donor (TTTS3D) and also with s-IUGR. These were treated by either selective laser photocoagulation of chorionic vessels (SLPCV) or cord coagulation (CC).

RESULTS

The 166 cases of TTTS3D were treated by SLPCV, whereas 23 and 22 cases of s-IUGR were treated by SLPCV and CC, respectively. Overall survival was 52.17% or 45.45% in s-IUGR treated by SLPCV or CC, respectively, and 48.49% in TTTS3D. The survival of appropriately grown for gestational age (AGA) twins following CC (90.9%) was higher than that following SLPCV in s-IUGR (74%) or in recipient twins of TTTS3D (55.42%) (p = 0.001). Survival of the IUGR twin was 30% and 41.56% with SLPCV in s-IUGR and TTTS3D, respectively.

CONCLUSIONS

Active management of severe IUGR with AREDF in the umbilical artery seems beneficial. Survival rates with SLPCV were similar in s-IUGR and TTTS3D. However, there was a trend for higher survival rates in the AGA twin for CC. The choice of the technique should be driven by objective counseling on survival of both IUGR and AGA twins and therefore by the utility-based ethical values expressed by the pregnant woman.

Blood flow changes in dichorionic twins with growth discordance

AIM

The study evaluated the applicability of Doppler ultrasonography in predicting the course of pregnancy and neonatal outcome in dichorionic pregnancy complicated by growth discordance.

METHODS

Doppler examination of the umbilical artery (UA) and middle cerebral artery (MCA) was performed in 106 twins. Abnormal values of the UA pulsatility index (PI) were considered to be above the 95th percentile and below 5th percentile for the MCA PI for gestational week. The difference of UA PI ~0.5 in twin pairs was considered abnormal. Doppler results were compared with selected parameters that characterize the course of pregnancy and fetal outcome.

RESULTS

Abnormal UA PI as well as the intertwine PI difference of 0.5 and more correlated significantly with lower gestational age at delivery, intertwine growth discordance of 35% or more, lower birth weight, and abnormal fetal outcome. The abnormal cerebra-umbilical(C/U) ratio correlated statistically with lower birth weight, abnormal fetal outcome, and an increased risk of premature delivery. There were no statistically significant differences in the majority of parameters that characterize the neonatal outcome between the groups with normal and abnormal MCA Pl.

CONCLUSION

The intertwine UA PI difference ~0.5 had the highest predictive value in the assessment of adverse fetal outcome and risk for small for gestational age (SGA). Relatively poor sensitivity was noted with regard to the abnormal values of UA PI and C/U ratio. The worse correlation was found in case of MCA Pl.

Undiagnosed xiphopagus twins: a perinatal malady

Conjoined twins are a very rare entity. It is associated with poor survival rate in the presence of vital organ sharing. The entity can be diagnosed as early as the first trimester. A conjoined twin diagnosed late in labor is a malady with high perinatal mortality and maternal morbidity. We present one such case of xiphopagus twins. The management of a case diagnosed late in labor can be very challenging. Such obstetric challenges can be avoided by a meticulous early scan with a high index of suspicion, especially in the absence of separating membrane while scanning multiple pregnancies.