Diffusion MRI findings in monochorionic twin pregnancies after intrauterine fetal death

Risk factors for brain injury in premature infants with twin-to-twin transfusion syndrome: a retrospective cohort study

Background

Brain injury (BI) is prevalent in premature infants with twin-to-twin transfusion syndrome (TTTS), while risk factors of BI in these patients remains unknown. Our study aims to discern potential risk factors that contribute to BI in premature infants with TTTS.

Methods

We conducted a retrospective cohort and analyzed clinical data of premature infants diagnosed with TTTS at the Northwest Women's and Children's Hospital between January 1, 2015 and January 1, 2020. Data included the infants' perinatal information, key postnatal examinations, laboratory tests, and treatments.

Results

Of the 84 patients enrolled in the study, 22 (26.2%) were categorized in the BI group and 62 (73.8%) in the non-BI group, based on cranial imaging. No significant differences were found at baseline between the groups in relation to the proportion of males (40.9% vs. 35.5%, P=0.845), median gestational age (weeks) [31.9 (31.5, 33.4) vs. 34.2 (31.6, 35.4), P=0.061], average weight (g) (1,676.4±567.5 vs. 1,845.2±511.7, P=0.200), maternal age (years) [29.5 (26.0, 31.0) vs. 28.5 (27.8, 31.0), P=0.656], the proportion of in-vitro fertilization (9.1% vs. 16.1%, P=0.648), cesarean sections (86.4% vs. 93.5%, P=0.549) or TTTS donor infants (50.0% vs. 51.6%, P=0.897). Multivariate logistic regression analysis indicated that invasive mechanical ventilation [invasive mechanical ventilation (IMV); odds ratio (OR) =4.365; 95% confidence interval (CI): 1.066-17.870; P=0.040], [necrotizing enterocolitis (NEC); OR =8.632; 95% CI: 1.542-48.318; P=0.014], [single intrauterine fetal demise (sIUFD); OR =14.067; 95% CI: 1.298-224.421; P=0.031], and a 5-minute Apgar score <9 (OR =4.663; 95% CI: 1.015-21.419; P=0.048) were strongly associated with BI in TTTS premature infants.

Conclusions

Our study identifies IMV, NEC, sIUFD, and a 5-minute Apgar score <9 as independent risk factors for BI in premature infants with TTTS.

Cutting-edge applications of fetal MR neuro-imaging in clinical routine: a pictorial essay

Over time, fetal MR neuro-imaging has undergone continuous improvement; presently, it plays a pivotal role in the diagnosis of an expanding array of complex neurological conditions. Within this pictorial essay, our focus will be exclusively directed towards those cutting-edge clinical applications, which currently yield valuable diagnostic insights on a single case basis. Specifically, the pictorial examples will center on some abnormal entities and their features at an earlier fetal stage.

Directive clinique no 440 : Prise en charge de la grossesse gémellaire monochoriale

OBJECTIF

Cette directive clinique passe en revue les données probantes sur la prise en charge de la grossesse gémellaire monochoriale normale et compliquée.

POPULATION CIBLE

Les femmes menant une grossesse gémellaire ou multiple de haut rang. BéNéFICES, RISQUES ET COûTS: L'application des recommandations de cette directive devrait améliorer la prise en charge des grossesses gémellaires (ou multiples de haut rang) monochoriales compliquées et non compliquées. Ces recommandations aideront les fournisseurs de soins à surveiller adéquatement les grossesses gémellaires monochoriales ainsi qu'à détecter et prendre en charge rapidement les complications associées de façon optimale afin de réduire les risques de morbidité et mortalité périnatales. Ces recommandations impliquent une surveillance échographique plus fréquente en cas de grossesse monochoriale qu'en cas de grossesse bichoriale. DONNéES PROBANTES: La littérature publiée a été colligée par des recherches dans les bases de données PubMed et Cochrane Library au moyen de termes MeSH pertinents (Twins, Monozygotic; Ultrasonography, Prenatal; Placenta; Fetofetal Transfusion; Fetal Death; Fetal Growth Retardation). Les résultats ont été restreints aux revues systématiques, aux essais cliniques randomisés et aux études observationnelles. Aucune date limite n'a été appliquée, mais les résultats ont été limités aux contenus en anglais ou en français. MéTHODES DE VALIDATION: Les auteurs principaux ont rédigé le contenu et les recommandations et ils se sont entendus sur ces derniers. Le conseil d'administration de la SOGC a approuvé la version définitive aux fins de publication. Les auteurs ont évalué la qualité des données probantes et la force des recommandations en utilisant le cadre méthodologique GRADE (Grading of Recommendations Assessment, Development and Evaluation). Voir l'annexe A en ligne (tableau A1 pour les définitions et tableau A2 pour l'interprétation des recommandations fortes et conditionnelles [faibles]). PROFESSIONNELS CONCERNéS: Spécialistes en médecine fœto-maternelle, obstétriciens, radiologues, échographistes, médecins de famille, infirmières, sages-femmes, résidents et autres fournisseurs de soins de santé qui s'occupent de femmes menant une grossesse gémellaire ou multiple de haut rang. RéSUMé POUR TWITTER: Directive canadienne (SOGC) pour le diagnostic, la surveillance échographique et la prise en charge des complications de la grossesse gémellaire monochoriale (p. ex., STT, TAPS, retard de croissance sélectif, cojumeau acardiaque, monoamnionicité et mort d'un jumeau). DÉCLARATIONS SOMMAIRES: RECOMMANDATIONS.

Guideline No. 440: Management of Monochorionic Twin Pregnancies

OBJECTIVE

This guideline reviews the evidence-based management of normal and complicated monochorionic twin pregnancies.

TARGET POPULATION

Women with monochorionic twin or higher order multiple pregnancies.

BENEFITS, HARMS, AND COSTS

Implementation of these recommendations should improve the management of both complicated and uncomplicated monochorionic (and higher order multiple) twin pregnancies. They will help users monitor monochorionic twin pregnancies appropriately and identify and manage monochorionic twin complications optimally in a timely manner, thereby reducing perinatal morbidity and mortality. These recommendations entail more frequent ultrasound monitoring of monochorionic twins compared to dichorionic twins.

EVIDENCE

Published literature was retrieved through searches of PubMed and the Cochrane Library using appropriate MeSH headings (Twins, Monozygotic; Ultrasonography, Prenatal; Placenta; Fetofetal Transfusion; Fetal Death; Fetal Growth Retardation). Results were restricted to systematic reviews, randomized 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 conditional [weak] recommendations).

INTENDED AUDIENCE

Maternal-fetal medicine specialists, obstetricians, radiologists, sonographers, family physicians, nurses, midwives, residents, and other health care providers who care for women with monochorionic twin or higher order multiple pregnancies.

TWEETABLE ABSTRACT

Canadian (SOGC) guidelines for the diagnosis, ultrasound surveillance and management of monochorionic twin pregnancy complications, including TTTS, TAPS, sFGR (sIUGR), acardiac (TRAP), monoamniotic twins and intrauterine death of one MC twin.

SUMMARY STATEMENTS

RECOMMENDATIONS.

Early detection of ischemic brain injuries by diffusion-weighted imaging after radiofrequency ablation for fetal reduction in monochorionic pregnancies

BACKGROUND

This study aimed to investigate the additional advantages of magnetic resonance imaging (MRI), particularly diffusion-weighted imaging (DWI) over fetal ultrasound in the detection of acute ischemic cerebral injuries in complicated monochorionic (MC) pregnancies that underwent selective reduction by radiofrequency ablation (RFA).

METHODS

This prospective cohort study was conducted on 40 women with complicated MC pregnancies who were treated by RFA. Fetal brain imaging by DWI and conventional MRI was performed either in the early (within 10 days after RFA) or late phase (after 3-6 weeks) in the surviving fetuses to detect both acute and chronic ischemic injuries. The presence of anemia after RFA was also evaluated by Doppler ultrasound.

RESULTS

Overall, 13 of the total 43 fetuses (30.23%) demonstrated MRI abnormalities with normal brain ultrasound results including germinal matrix hemorrhage (GMH), extensive cerebral ischemia, and mild ventriculomegaly. Although seven fetuses with GMH eventually survived, fetuses that demonstrated ischemic lesions and ventriculomegaly on MRI died in the uterus.

CONCLUSION

The absence of abnormal cerebral lesions or anemia on ultrasound and Doppler exams does not necessarily rule out fetal brain ischemia. Performing early MRI, particularly DWI seems to be a reasonable option for detection of early intracranial ischemic changes and better management of complicated multiple pregnancies which were treated by RFA.

Incidence and outcome of prenatal brain abnormality in twin-to-twin transfusion syndrome: systematic review and meta-analysis

OBJECTIVES

To evaluate the incidence of antenatally diagnosed brain injury in twin pregnancy complicated by twin-to-twin transfusion syndrome (TTTS) and to quantify the perinatal mortality, morbidity and long-term neurodevelopmental outcome of these fetuses.

METHODS

MEDLINE, EMBASE, ClinicalTrials.gov and The Cochrane Library databases were searched. Inclusion criteria were studies reporting on brain abnormality diagnosed antenatally in twin pregnancies complicated by TTTS. The primary outcome was the incidence of prenatal brain abnormality. The secondary outcomes were intrauterine demise (IUD), neonatal death, termination of pregnancy (TOP) and long-term morbidity. Outcomes were explored in the population of fetuses with antenatal diagnosis of brain abnormality. Subgroup analysis according to the type of treatment, gestational age, Quintero stage at diagnosis and/or treatment, and cotwin death was planned. Meta-analysis of proportions was used to combine data and pooled proportions and their 95% CI were reported.

RESULTS

Thirteen studies including 1573 cases of TTTS and 88 fetuses with an antenatal diagnosis of brain abnormality were included in the systematic review. The meta-analysis included only studies reporting on brain abnormality in twin pregnancy complicated by TTTS cases and treated with laser surgery. Overall, brain injury occurred in 2.2% (52/2410) of fetuses (eight studies). Brain abnormality was reported in 1.03% and 0.82% of recipients and donors, respectively. The most common type of abnormality was ischemic lesions (30.4% (95% CI, 19.1-43.0%)), followed by destructive lesions (23.9% (95% CI, 13.7-35.9%)), ventriculomegaly (19.9% (95% CI, 10.6-31.3%)) and hemorrhagic lesions (15.3% (95% CI, 7.1-25.8%)). Spontaneous IUD occurred in 13.4% (95% CI, 5.1-24.8%) of fetuses, while TOP was chosen by parents in 53.5% (95% CI, 38.9-67.8%) cases. Neonatal death was reported by only three studies, with an incidence of 15.4% (95% CI, 2.8-35.4%). Finally, only two studies reported on composite morbidity, with an overall rate of the outcome of 20.4% (95% CI, 2.5-49.4%) and rates of 29.7% and 20.4% in the recipient and donor fetuses, respectively. Due to the small numbers, only composite morbidity was analyzed and no information on neonatal intensive care unit admission, respiratory distress syndrome or other long-term outcomes, such as neurodevelopmental delay and cerebral palsy, could be retrieved reliably.

CONCLUSIONS

The overall incidence of antenatally diagnosed fetal brain abnormality in twin pregnancy complicated by TTTS treated with laser surgery is around 2% and is mainly ischemic in nature (30.4%). TOP was chosen by parents in more than half of cases (53.5%). No information could be retrieved on morbidity outcomes, highlighting the urgent need for long-term follow-up studies of these children. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Early imaging predictors of fetal cerebral ischemic injury in monochorionic twin pregnancy complicated by spontaneous single intrauterine death

OBJECTIVE

Monochorionic twin pregnancies are at increased risk of single intrauterine death (sIUD) and subsequent brain injury in the surviving twin owing to shared placentation. We assessed the association between middle cerebral artery peak systolic velocity (MCA-PSV) and cerebral injury on magnetic resonance imaging (MRI) and examined the association between cerebral findings on diffusion-weighted imaging (DWI) and those on T2-weighted imaging following spontaneous sIUD.

METHODS

This was a retrospective cohort study of monochorionic pregnancies complicated by spontaneous sIUD followed at a tertiary center between January 2008 and January 2020. Pregnancies with sIUD following laser treatment, those with selective feticide, double IUD occurring on the same day or sIUD before 14 weeks' gestation were excluded, as were cases in which MCA-PSV was not measured or DWI-MRI was not performed. The ability of MCA-PSV Doppler to predict subsequent cerebral injury on MRI was assessed, and DWI findings were analyzed and compared with those on susceptibility-weighted imaging (SWI) and T2-weighted MRI to determine its diagnostic accuracy.

RESULTS

We assessed 64 monochorionic pregnancies complicated by spontaneous sIUD. Of these, 47 (73.4%) pregnancies underwent fetal brain MRI and met the inclusion criteria. Sixteen (34.0%) of these fetuses demonstrated cerebral injury on MRI. The median interval between the diagnosis of sIUD and MRI examination was 5 days. Fetuses with increased MCA-PSV > 1.5 multiples of the median (MoM) following sIUD were significantly more likely to demonstrate cerebral injury on MRI than were those with normal MCA-PSV (68.8% vs 38.7%; P = 0.05). The sensitivity and specificity of MCA-PSV > 1.5 MoM for predicting cerebral injury on MRI were 68.8% (95% CI, 41.3-88.9%) and 61.3% (95% CI, 42.2-78.2%), respectively. Patterns of early cerebral injury on T2-weighted and SWI-MRI included acute or subacute tissue swelling (n = 6), parenchymal atrophy (n = 7), loss of cortical ribbon (n = 1) and hemorrhage (n = 8). Early MRI within approximately 2 weeks after the diagnosis of sIUD demonstrated abnormal DWI along with coexisting SWI and T2-weighted sequelae in 56.3% (9/16) of cases. When DWI was normal and a second MRI examination was performed later (n = 7), there were no ischemic changes evident on T2-weighted imaging.

CONCLUSIONS

Increased MCA-PSV is associated with, but predicts poorly, cerebral injury after sIUD. Early MRI with DWI within approximately 2 weeks after the diagnosis of sIUD is valuable in identifying any cerebral injury. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Third Trimester Structural and Diffusion Brain Imaging after Single Intrauterine Fetal Death in Monochorionic Twins: MRI-Based Cohort Study

BACKGROUND AND PURPOSE

Single intrauterine fetal death increases the risk of antenatal brain lesions in the surviving twin. We evaluated the prevalence of structural brain lesions, biometry, and diffusivity on routine third trimester MR imaging performed following single intrauterine fetal death.

MATERIALS AND METHODS

In a retrospective MR imaging-based cohort study, we compared 29 monochorionic twins complicated with single intrauterine fetal death (14 following laser ablation treatment for twin-to-twin transfusion syndrome, 8 following selective fetal reduction, and 7 spontaneous) with 2 control cohorts (49 singleton fetuses and 28 uncomplicated twin fetuses). All fetuses in the single intrauterine fetal death group underwent fetal brain MR imaging as a routine third trimester evaluation. Structural brain lesions were analyzed. Cerebral biometry and diffusivity were measured and compared.

RESULTS

Brain lesions consistent with the evolution of prior ischemic injury were found in 1 of 29 fetuses, not detected by ultrasound. No acute brain infarction, hemorrhage, or cortical abnormalities were found. Supratentorial biometric measurements in the single intrauterine fetal death group were significantly smaller than those in the singleton group, but not significantly different from those in the uncomplicated twin group. There were no significant differences in ADC values of the cerebral hemispheres, basal ganglia, and pons between the single intrauterine fetal death group and either control group.

CONCLUSIONS

Although smaller brain biometry was found, normal diffusivity in surviving twins suggests normal parenchymal microstructure. The rate of cerebral structural injury was relatively low in our cohort, arguing against the routine use of fetal brain MR imaging in twin pregnancies complicated with single intrauterine fetal death. Larger prospective studies are necessary to guide appropriate surveillance protocol and parental counseling in twin pregnancies complicated by single intrauterine fetal death.

Imaging diagnosis and legal implications of brain injury in survivors following single intrauterine fetal demise from monochorionic twins - a review of the literature

Brain injury of the surviving twin from monochorionic pregnancies following intrauterine fetal demise during the second and third trimesters is a rare but severe complication. Monochorionicity and gestational age at the time of stillbirth seem to be decisive factors in terms of long-term neurologic outcome prediction for the survivor. Magnetic resonance imaging (MRI), diffusion weighted imaging (DWI) in particular, seem to bring the earliest and most accurate diagnosis. Ultrasound detection of brain damage is possible in later stages of fetal brain injury. It is essential to provide early diagnosis and multidisciplinary counsel to the parents to ensure informed decision making. For couples who choose to terminate pregnancy legislation related to late abortion might lead to further distress. Our paper aims to stress the importance of MRI DWI in the evaluation of surviving twins following single intrauterine fetal demise in monochorionic pregnancies and the delicate context of the medical professionals and parents facing this clinical situation, sometimes complicated by legal constraints.

The prevalence of brain lesions after in utero surgery for twin-to-twin transfusion syndrome on third-trimester MRI: a retrospective cohort study

OBJECTIVE

Due to the increased risk of antenatal brain lesions, we offer a third-trimester magnetic resonance imaging (MRI) scan to all patients who underwent an in utero intervention for twin-twin transfusion syndrome (TTTS). However, the usefulness of such a policy has not been demonstrated yet. Therefore, we determined the prevalence of antenatal brain lesions detected on third-trimester MRI and the proportion of lesions detected exclusively on MRI.

MATERIALS AND METHODS

We conducted a retrospective cohort study of monochorionic diamniotic twin pregnancies complicated by TTTS that underwent laser coagulation of the vascular anastomoses or fetal reduction by umbilical cord occlusion between 2010 and 2017. We reviewed the third-trimester MRI findings and compared those with the prenatal ultrasonography.

RESULTS

Of the 141 patients treated with laser coagulation and 17 managed by cord occlusion, 112/141 (79%) and 15/17 (88%) patients reached 28 weeks. Of those, 69/112 (62%) and 11/15 (73%) underwent an MRI between 28 and 32 weeks. After laser coagulation, MRI detected an antenatal brain lesion in 6 of 69 pregnancies (9%) or in 6 of 125 fetuses (5%). In 4 cases (67%), the lesion was detected only on MRI. In the 11 patients treated with cord occlusion, no brain lesions were diagnosed.

CONCLUSION

The prevalence of brain lesions detected by third-trimester MRI is higher compared to prenatal ultrasonography alone, making MRI a useful adjunct to detect antenatal brain lesions in twin pregnancies after in utero treatment for TTTS.

KEY POINTS

• In utero interventions for twin-to-twin transfusion syndrome (TTTS) do not prevent the occurrence of antenatal brain lesions. • Fetal magnetic resonance imaging (MRI) has high accuracy in detecting anomalies of cortical development and can be a useful adjunct to ultrasonography in diagnosing certain brain abnormalities. • After laser coagulation of the anastomoses for TTTS, third-trimester MRI diagnosed a brain lesion that was not detected earlier on ultrasound scan in 6% of pregnancies.

In Utero Diffusion MRI: Challenges, Advances, and Applications

In utero diffusion magnetic resonance imaging (MRI) provides unique opportunities to noninvasively study the microstructure of tissue during fetal development. A wide range of developmental processes, such as the growth of white matter tracts in the brain, the maturation of placental villous trees, or the fibers in the fetal heart remain to be studied and understood in detail. Advances in fetal interventions and surgery furthermore increase the need for ever more precise antenatal diagnosis from fetal MRI. However, the specific properties of the in utero environment, such as fetal and maternal motion, increased field-of-view, tissue interfaces and safety considerations, are significant challenges for most MRI techniques, and particularly for diffusion. Recent years have seen major improvements, driven by the development of bespoke techniques adapted to these specific challenges in both acquisition and processing. Fetal diffusion MRI, an emerging research tool, is now adding valuable novel information for both research and clinical questions. This paper will highlight specific challenges, outline strategies to target them, and discuss two main applications: fetal brain connectomics and placental maturation.

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.

MRI features of the placenta in fetuses with and without CNS abnormalities

AIM

To investigate if magnetic resonance imaging (MRI) features of the placenta are different in fetuses with and without central nervous system (CNS) abnormalities.

MATERIAL AND METHODS

Institutional research ethics board approval was obtained. Fetal MRI of 97 singleton pregnancies were analysed retrospectively (19-25 weeks gestation), 65 with CNS morphological abnormalities and 32 controls. Placental T2 signal intensity, placental and fetal volumes, placental-to-fetal volume ratio, and placental apparent diffusion coefficient (ADC) values were assessed. Measurements were compared with the presence or absence of CNS fetal abnormalities using the Mann-Whitney test. Separate slopes models and intercept models were used to check for significant differences in the slopes and intercepts, respectively, among the groups.

RESULTS

Placental ADC values were significantly lower in placentas of fetuses with CNS abnormalities compared to controls (p=0.04). Placental T2 signal intensity, fetal and placental volumes did not differ between the two groups. The rate of increase in fetal-to-placental volume ratio with gestational age (GA) was greater among the controls.

CONCLUSION

The presence of fetal CNS abnormalities is associated with reduced ADC values of the placenta. Moreover, placentas of fetuses with CNS abnormalities show a less rapid increase in fetal to placental volume ratio with GA. Therefore, ADC mapping, as well as different growth kinetics of the placenta relative to the fetus, may potentially serve as early markers of pathological neurodevelopment.

Brain-injured Survivors of Monochorionic Twin Pregnancies Complicated by Single Intrauterine Death: MR Findings in a Multicenter Study

Purpose To describe and classify the range of brain injuries present at prenatal, in-utero magnetic resonance (MR) imaging in co-twin survivors of monochorionic (MC) twin pregnancies complicated by single intrauterine death (SIUD). Materials and Methods This retrospective, observational study from six tertiary fetal medicine centers that perform tertiary-level prenatal in-utero MR studies reviewed cases in which prenatal in-utero MR imaging had shown a brain injury in a surviving co-twin of a twin pregnancy with a MC component complicated by SIUD. Results Forty-two surviving MC twins were described. The primary distinction of brain abnormalities was into nonfocal and focal lesions. The nonfocal lesions included periventricular leukomalacia (group 1; two fetuses), generalized encephalomalacia (group 2; nine fetuses), posterior encephalomalacia (group 3; seven fetuses), and bilateral parasagittal and perisylvian injury (group 4; three fetuses). The focal lesions included nonhemorrhagic lesions (group 5; 14 fetuses) and hemorrhagic lesions (group 6; seven fetuses). Focal brain lesions were more likely to be found in the surviving MC pregnancies complicated by twin-twin transfusion syndrome (TTTS) (odds ratio, 2.4; 95% confidence interval: 1.3, 18.5; P = .01) and in fetuses that underwent an obstetric intervention (odds ratio, 2.8; 95% confidence interval: 1.8, 23.6; P = .006). Conclusion Brain injury of the surviving co-twin after SIUD in MC pregnancies is usually of ischemic origin and spares the brainstem and cerebellum. Focal brain lesions are more frequent in pregnancies complicated by TTTS or in those where an intervention has been performed.

Apparent Diffusion Coefficient of the Placenta in Twin versus Singleton Pregnancies

Previous studies in singleton pregnancies reported conflicting trends in apparent diffusion coefficient (ADC) values with gestational age (GA) and stable relative ADC (rADC; ADC placenta divided by ADC globe) throughout pregnancy. The purpose of our study was to compare the ADC and rADC of placentas of twin and singleton pregnancies.

MATERIALS AND METHODS

Fetal MRI of 11 twin and 23 singleton pregnancies were retrospectively analyzed. Each group was further divided by GA (≤24 and >24 weeks). On ADC, 3 regions of interest were selected in the placenta and 1 in the globe. ADC and rADC measurements were compared between different GA and between singleton and twin placentas.

RESULTS

No significant difference was shown between ADC and rADC values of singleton and twin placentas as well as between ADC and rADC values of singleton and twin placentas at different GA. No significant difference was shown when accounting for both GA and number of fetuses.

CONCLUSION

The diffusion characteristics of twin placentas are similar to those of singleton placentas. ADC and rADC remain stable throughout pregnancy in twin and singleton placentas, reflecting stable extracellular water diffusion, despite changes associated with placental maturation.

Fetal Brain Injury in Survivors of Twin Pregnancies Complicated by Demise of One Twin: A Review

Perinatal mortality is increased considerably in multiple pregnancies compared to singleton pregnancies, with single intrauterine fetal demise (sIUFD) presenting a rare but unique perinatal problem. Monochorionic pregnancies are at particular risk of sIUFD due to bidirectional inter-twin placental vascular anastomoses. The resulting inter-twin blood flow can become unbalanced, causing acute and chronic inter-twin transfusion and profound anemia secondary to fetal exsanguination into the low-pressure circulation of the dead fetus. If the sIUFD occurs after 14 weeks’ gestation it is believed to have the most significant effect on the continuing pregnancy as the co-twin is at increased risk of preterm delivery, long-term neurological complications, and death. This article will focus on fetal brain injury in the surviving co-twin in the case of sIUFD, as it is the most common kind of injury in sIUFD, and one which concerns parents and may be the basis for terminating the pregnancy. We will outline how these brain injuries are thought to occur and describe potential pathophysiological mechanisms. We will discuss risk factors for brain injury in cases of sIUFD, including: chorionicity, cause of the sIUFD (spontaneous or secondary to an underlying pathological process such as twin-to-twin transfusion syndrome), gestation of delivery and how to prevent brain injury in the co-twin. We also review modes of imaging, discuss the difficulties in predicting the long-term outcome for co-twin survivors, and highlight the dearth of research in this area.

Decreased Brain and Placental Perfusion in Omphalopagus Conjoined Twins on Fetal MRI

The aim of this study is to evaluate perfusional changes in brain and placenta of omphalopagus conjoined twins and to compare them with singleton fetuses by using diffusion weighted imaging and apparent diffusion coefficient. Fetal MRIs of 28-week-old omphalopagus conjoined twins with a shared liver with two separate gallbladders and portal and hepatic venous systems and three singleton fetuses with unilateral borderline ventriculomegaly at the same gestational week as control group were enrolled retrospectively. There was a significant decrease in ADC values of brain regions (p = 0.018) and placenta (p = 0.005) of conjoined twins compared to the control group. The decreased ADC values in placenta and brain regions in conjoined twins might be due to decreased placental perfusion compared to singleton pregnancy. Our results would be a keystone for future studies which will compare larger group of monochorionic multiple pregnancies with singleton pregnancies.

Cerebral Lesions at Fetal Magnetic Resonance Imaging and Neurologic Outcome After Single Fetal Death in Monochorionic Twins

Background: Single fetal death (sFD) in monochorionic twin pregnancies is associated with substantial morbidity and mortality in the survivor. The aim of our study was to evaluate the rate of cerebral lesions detected at fetal Magnetic Resonance Imaging (MRI) and to correlate the results with the neurologic outcome of the survivors of monochorionic twin pregnancies after sFD. Methods: Between 2005 and 2012, 11 monochorionic twin pregnancies with sFD and subsequent fetal MRI of the survivor were included. All neonates underwent neurologic assessment after birth and 56% of surviving infants underwent long-term neurologic assessment. MRI findings and neurologic outcome of the survivors were evaluated. Results: Gestational age at sFD was 20.9 (±2.9) weeks; 55% (6/11) of survivors of monochorionic twin pregnancies after sFD showed cerebral lesions at fetal MRI; 72% (8/11) of all survivors had normal neonatal neurologic outcome: all survivors with normal fetal MRI and 50% of survivors with cerebral lesions at fetal MRI. Long-term neurologic assessment was normal in all tested patients with normal fetal MRI and in one of three tested patients with cerebral lesions at fetal MRI. Conclusion: Survivors of monochorionic twin pregnancies after sFD show a high rate of cerebral lesions at fetal MRI. The importance of cerebral lesions at fetal MRI in survivors after sFD in monochorionic twin pregnancies is uncertain. All tested survivors with normal fetal MRI showed normal neurologic outcome but only one of three survivors with cerebral lesions at fetal MRI showed normal long-term neurologic outcome.

Normal fetal posterior fossa in MR imaging: new biometric data and possible clinical significance

BACKGROUND AND PURPOSE

Posterior fossa malformations are a common finding in prenatal diagnosis. The objectives of this study are to re-evaluate existing normal MR imaging biometric data of the fetal posterior fossa, suggest and evaluate new parameters, and demonstrate the possible clinical applications of these data.

MATERIALS AND METHODS

This was a retrospective review of 215 fetal MR imaging examinations with normal findings and 5 examinations of fetuses with a suspected pathologic posterior fossa. Six previously reported parameters and 8 new parameters were measured. Three new parameter ratios were calculated. Interobserver agreement was calculated by using the intraclass correlation coefficient.

RESULTS

For measuring each structure, 151-211 MR imaging examinations were selected, resulting in a normal biometry curve according to gestational age for each parameter. Analysis of the ratio parameters showed that vermian lobe ratio and cerebellar hemisphere ratio remain constant with gestational age and that the vermis-to-cisterna magna ratio varies with gestational age. Measurements of the 5 pathologic fetuses are presented on the normal curves. Interobserver agreement was excellent, with the intraclass correlation coefficients of most parameters above 0.9 and only 2 parameters below 0.8.

CONCLUSIONS

The biometry curves derived from new and existing biometric data and presented in this study may expand and deepen the biometry we use today, while keeping it simple and repeatable. By applying these extensive biometric data on suspected abnormal cases, diagnoses may be confirmed, better classified, or completely altered.

Early detection by diffusion-weighted sequence magnetic resonance imaging of severe brain lesions after fetoscopic laser coagulation for twin-twin transfusion syndrome

OBJECTIVE

Monochorionic twins treated by fetoscopic laser coagulation (FLC) for twin-twin transfusion syndrome (TTTS) are at increased risk of neurodevelopmental impairment. Our aim was to evaluate the additional value of diffusion-weighted imaging (DWI) over fetal sonography and T2 magnetic resonance imaging (MRI) in the detection of acute ischemic cerebral lesions shortly following FLC.

METHODS

This was a prospective cohort study of fetuses with TTTS treated by FLC. All fetuses underwent brain DWI and T2-MRI within 24-96 h after the procedure and a follow-up MRI at 30-32 weeks' gestation. All fetuses also had frequent ultrasound evaluation until delivery.

RESULTS

Thirty pregnancies with TTTS were included in the study. Eight resulted in survival of only one twin after the procedure (Group A), while the other 22 pregnancies resulted in the survival of both twins (Group B), as assessed at the time of initial MRI. Two fetuses in Group A and four in Group B had evidence of transient bleeding in the germinal matrix. Three fetuses in Group B and none in Group A had diffuse ischemic changes in the white matter. One fetus died in utero 24 h after MRI. The other two fetuses in Group B demonstrated an acute infarct 24-48 h after the procedure. Subsequent scans at 28-29 and 32 weeks showed brain atrophy compatible with an old infarct.

CONCLUSIONS

DWI can demonstrate cerebral damage immediately after FLC. Larger cohorts are needed to determine the role of fetal MRI in the prenatal assessment and follow-up of patients with TTTS.

Encephalomalacia in surviving twin after single fetal death diagnosed at 18 weeks of gestation in monochorionic twin pregnancy

Patient: Female, 28

Final Diagnosis: Single intrauterine fetal death

Symptoms: —

Medication: —

Clinical Procedure: —

Specialty: Obstetrics and Gynecology