Medicine
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This repository contains the published and unpublished research of the Faculty of Medicine by the staff members of the faculty
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Item Ultrasound estimation of birthweight in twin pregnancy: comparison of biometry algorithms in the STORK multiple pregnancy cohort.(Wiley, 2014) Khalil, A.; D'Antonio, F.; Dias, T.; Cooper, D.; Thilaganathan, B.; Southwest Thames Obstetric Research Collaborative (STORK)OBJECTIVES: The aims of this study were first, to ascertain the accuracy of formulae for ultrasonographic birth-weight estimation in twin compared with singleton pregnancies and second, to assess the accuracy of sonographic examination in the prediction of birth-weight discordance in twinpregnancies. METHODS: This was a retrospective cohort study including both singleton and twin pregnancies. Routine biometry was recorded and estimated fetalweight (EFW) calculated using 33 different formulae. Only pregnancies that delivered within 48 h of the ultrasound scan were included (4280 singleton and 586 twin fetuses). Differences between the EFW and actual birth weight (ABW) were assessed by percentage error, accuracy in predictions within ± 10 % and ± 15% of error and use of the Bland-Altman method. The accuracy of prediction of the different cut-offs of birth-weight discordance intwin pregnancies was also assessed using the area under the receiver-operating characteristics curve (AUC). RESULTS: The overall mean absolute percentage error was ≤ 10 % for 25 formulae in singleton pregnancies compared with three formulae in twinpregnancies. The overall predictions within ± 10% and ± 15% of the ABW were 62.2% and 81.5% in singleton and 49.7% and 68.5% in twinpregnancies, respectively. When the formulae were categorized according to the biometric parameters included, those based on a combination of head, abdomen and femur measurements showed the lowest mean absolute percentage error, in both singleton and twin pregnancies. The predictive accuracy for 25% birth-weight discordance using the Hadlock 2 formula, as assessed by the AUC, was 0.87. CONCLUSIONS: Ultrasound estimation of birth weight is less accurate in twin than in singleton pregnancies. Formulae that include a combination of head, abdomen and femur measurements perform best in both singleton and twin pregnancies.Item Weight discordance and perinatal mortality in twins: analysis of the Southwest Thames Obstetric Research Collaborative (STORK) multiple pregnancy cohort(Wiley, 2013) D'Antonio, F.; Khalil, A.; Dias, T.; Thilaganathan, B.; Southwest Thames Obstetric Research Collaborative (STORK)OBJECTIVES: The degree of actual intertwin birth weight (BW) or ultrasound estimated fetal weight (EFW) discordance that justifies elective delivery is yet to be established. The main aim of this study was to ascertain the performance of BW and ultrasound EFW discordance in the prediction ofperinatal loss in twin pregnancies. METHODS: This was a retrospective study of all twin pregnancy births from a large regional cohort of nine hospitals over a 10-year period. Intertwin BW and ultrasound EFW discordance were analyzed in relation to the occurrence of stillbirth or neonatal death of one or both twins from 26 weeks' gestation as obtained from a mandatory national register. Receiver-operating characteristics (ROC), survival and logistic regression analyses were performed to evaluate the contribution of weight discordance in determining perinatal loss. RESULTS: A total of 2161 twin pregnancies were included in the analysis. The area under the ROC curve for the prediction of perinatal loss was similar for BW and ultrasound EFW discordance (P = 0.62). Kaplan-Meier analysis showed that twins with BW or EFW of ≥ 25% discordance had a significantly lower survival trend than did those with lesser degrees of discordance (P < 0.001). The hazard ratios for the risk of total perinatal loss intwins with a BW or EFW discordance of ≥ 25% were 7.29 (95% CI, 4.37-12.00) and 7.28 (95% CI, 4.46-11.92), respectively. Logistic regression analysis demonstrated that BW discordance and gestational age, but not chorionicity or individual fetal size percentile, were independently associated with perinatal mortality. CONCLUSIONS: An EFW discordance of ≥ 25% represents the optimal cut-off for the prediction of stillbirth and neonatal mortality irrespective of chorionicity or individual fetal size. A policy of increased fetal surveillance commencing from 26 weeks' gestation might be reasonable for pregnancies beyond this cut-off, but this would require confirmation in large-scale prospective trials. Copyright © 2013 ISUOG. Published by John Wiley & Sons LtdItem Does antenatal ultrasound labeling predict birth order in twin pregnancies?(Wiley, 2013) D'Antonio, F.; Dias, T.; Thilaganathan, B.; Southwest Thames Obstetric Research Collaborative (STORK)OBJECTIVE: It is often assumed by obstetricians, neonatologists and parents that the prenatal nomenclature used to identify twins on ultrasound is consistent with twin labeling after their birth. The aim of this study was to use a large regional database of twin ultrasound scans to validate the effectiveness of a scan before delivery in predicting twin birth-order. METHODS: A large regional database of twin ultrasound scans with data from nine hospitals over a 10-year period was used to identify all ultrasound examinations carried out just before birth. The discordance in twin order between the last scan and birth was evaluated by observing discrepancies in fetal sex and weight. RESULTS: In total, 2103 twin pregnancies with ultrasound estimated fetal weights (EFWs) and birth weights were assessed. Of these, fetal sex was recorded in 149 different-sex pregnancies. Discrepancy between antenatal labeling and the anticipated birth order was noted in 37.6% (56/149) of cases when judged by sex discordance and in 36% (757/2103) of cases when judged by weight discordance. Multiple logistic regression analyses demonstrated that weight discordance, but not chorionicity, scan-to-delivery interval, gestation at scan or gestation at delivery, significantly influenced the change in birth order (P < 0.001). CONCLUSION: Antenatal ultrasound labeling does not predict twin birth-order in a significant proportion of twin deliveries. This finding should be borne in mind not only by parents, but also by physicians when delivering twins discordant for anomalies that are not evident on external examinationItem Early fetal loss in monochorionic and dichorionic twin pregnancies: analysis of the Southwest Thames Obstetric Research Collaborative (STORK) multiple pregnancy cohort(Wiley, 2013) D'Antonio, F.; Khalil, A.; Dias, T.; Thilaganathan, B.; Southwest Thames Obstetric Research Collaborative (STORK)OBJECTIVES: Monochorionic (MC) twins are at increased risk of early fetal loss secondary to vascular complications such as twin-twin transfusion syndrome (TTTS). This study compared the early perinatal loss rates between MC and dichorionic (DC) twins in an era of invasive treatment for TTTS. METHODS: This was a retrospective study of all twin pregnancies of known chorionicity from a large regional cohort of nine hospitals over a 10-year period. Ultrasound data were matched to hospital delivery records and to a mandatory national register of pregnancy losses. Prospective risk of pregnancy loss from 14 to 24 weeks' gestation was calculated and the survival trend of MC and DC twins was analyzed using Kaplan-Meier survival analysis. RESULTS: The analysis included 3117 twin pregnancies (605 MC and 2512 DC). The total risk of early pregnancy loss (miscarriage and neonatal death) before 24 weeks was significantly higher in MC twins (60.3 per 1000 fetuses) than in DC twins (6.6 per 1000 fetuses), with a relative risk of 9.18 (95% CI, 6.0-13.9). Survival analysis showed a significant difference in overall and early mortality between MC and DC twins (log-rank test, P < 0.0001), while no difference was noted after 24 weeks' gestation (log-rank test, P = 0.08). CONCLUSIONS: Early pregnancy loss is significantly more common in MC than in DC twins, but no difference in the prospective risk of mortality between MC and DC twins is evident after 24 weeks' gestation. The observed early mortality rate has almost halved in comparison with previous studies in the published literature. Early detection and prompt treatment of complications in MC twins are likely to have contributed to this improvement in outcome. Copyright © 2012 ISUOG. Published by John Wiley & Sons Ltd.Item Crown-rump length discordance and adverse perinatal outcome in twins: analysis of the Southwest Thames Obstetric Research Collaborative (STORK) multiple pregnancy cohort.(Wiley, 2013) Dias, T.; Thilaganathan, B.OBJECTIVE: Evidence for the role of first-trimester ultrasound in predicting outcome in twin pregnancies is conflicting. The aim of this study was to determine the association between crown-rump length (CRL) discordance and adverse perinatal outcome in twin pregnancies. METHODS: This was a retrospective study of all twin pregnancies of known chorionicity from a large regional cohort over a 10-year period. Terminations of pregnancy, cases with fetal or chromosomal abnormalities and monoamniotic pregnancies were excluded. Receiver-operating characteristics (ROC) curve and logistic regression analyses were performed to evaluate the association between CRL discordance and stillbirth, neonatal mortality, intrauterine growth restriction, preterm birth (PTB) at < 34 weeks' gestation and birth weight (BW) and ultrasound estimated fetal weight (EFW) discordance of ≥ 25%. RESULTS: A total of 2155 twin pregnancies were analyzed, of which 420 were monochorionic (MC) and 1735 dichorionic (DC). There were 42 fetal losses before 24 weeks' gestation and 23 perinatal deaths. CRL discordance was poorly predictive for fetal loss at < 24 weeks (area under the ROC curve (AUC), 0.54 (95% CI, 0.46-0.62)), perinatal loss (AUC, 0.52 (95% CI, 0.41-0.64)), BW discordance (AUC, 0.61 (95% CI, 0.56-0.65)), BW < 5(th) centile (AUC, 0.56 (95% CI, 0.53-0.59)), EFW discordance (AUC, 0.55 (95% CI, 0.51-0.60)) and PTB at < 34 weeks (AUC, 0.50 (95% CI, 0.47-0.54)). Overall mortality was significantly higher in MC (5.0%) than in DC (2.6%) twins (P = 0.016). Logistic regression analysis demonstrated that chorionicity (odds ratio 2.09 (95% CI, 1.06-4.10); P = 0.033) independently contributed to determining mortality, while CRL discordance (P = 0.201) did not. Adjusting for chorionicity did not improve the detection of adverse outcomes using CRL discordance. CONCLUSION: In the absence of aneuploidy or structural fetal abnormality, CRL discordance is of poor predictive value for adverse perinatal outcome in both MC and DC twin pregnancies. CRL discordance should not be used routinely to identify twin pregnancies at high risk of adverse perinatal outcome. Copyright © 2013 ISUOG. Published by John Wiley & Sons Ltd.Item Elective birth at 37 weeks of gestation versus standard care for women with an uncomplicated twin pregnancy at term: the Twins Timing of Birth Randomised Trial(Wiley, 2012) Dias, T.; Thilaganathan, B.No Abstract avialableItem Prediction of selective fetal growth restriction and twin-to-twin transfusion syndrome in monochorionic twins(Wiley, 2012) Memmo, A.; Dias, T.; Mahsud-Dornan, S.; Papageorghiou, A. T.; Bhide, A.; Thilaganathan, B.OBJECTIVE: To study the correlation of discrepancy between crown-rump length (CRL) and nuchal translucency (NT) in monochorionic twins at 11-14 weeks of gestation and subsequent development of twin-to-twin transfusion syndrome (TTTS) and selective fetal growth restriction (sFGR). DESIGN: Retrospective cohort study. SETTING: Tertiary-care Fetal Medicine Unit, London. SAMPLE: Monochorionic twin pregnancies with known outcome. METHODS: Inter-twin discrepancy was calculated as a percentage of the larger CRL and smaller NT and compared among those developing TTTS, those with sFGR and those with normal outcome. Receiver operating characteristic (ROC) curves were constructed to evaluate the performance of inter-twin discrepancy in prediction of sFGR and TTTS. MAIN OUTCOME MEASURES: Development of TTTS and sFGR. RESULTS: A total of 242 monochorionic twin pregnancies were studied (102 TTTS, 36 sFGR and 104 controls). The median CRL discrepancy in the sFGR group (11.9%) was significantly higher (P < 0.001) than in the TTTS group (3.8%) and control group (3.5%). Median inter-twin NT discrepancies were not significantly different (P = 0.869) between sFGR and both TTTS and control groups (15.6%, 16.7% and 14.8%, respectively). Discrepancy in CRL performs well as a screening test for sFGR (area under ROC curve = 0.89), but not for TTTS (area under ROC curve = 0.58). CONCLUSIONS: First-trimester CRL discrepancy in monochorionic twins is a marker for subsequent development of sFGR rather than TTTS. Inter-twin NT discrepancy does not appear to be significantly different in these two groups from those with normal outcome.Item First-trimester ultrasound determination of chorionicity in twin pregnancy(Wiley, 2011) Dias, T.; Arcangeli, T.; Bhide, A.; Napolitano, R.; Mahsud-Dornan, S.; Thilaganathan, B.OBJECTIVE: To determine the accuracy of ultrasound at 11-14 weeks' gestation in the diagnosis of chorionicity in twin pregnancy. METHODS:This was a retrospective observational study of data obtained between 1999 and 2010. At the first-trimester routine ultrasound scan,chorionicity was assigned according to the number of placental masses and T or λ-signs for a single placental mass. Chorionicity was confirmed by histology or discordant sex at birth. RESULTS: A total of 648 pregnancies were assigned chorionicity by first-trimester ultrasound during the study period. Chorionicity was ascertained in 613 cases, either by histology (n = 340) or discordant sex (n = 273). Chorionicity was correctly assigned by ultrasound at 11-14 weeks in 612 of 613 pregnancies (accuracy 99.8%). Sensitivity and specificity for determining monochorionicity were 100% and 99.8%, respectively.CONCLUSIONS:First-trimester ultrasound can be used to determine chorionicity reliably by noting the number of placental masses and T or λ-signs.Determination of twin chorionicity is important and should be completed in the first trimester.Item Second-trimester assessment of gestational age in twins: validation of singleton biometry charts(Wiley, 2011) Dias, T.; Arcangeli, T.; Bhide, A.; Mahsud-Dornan, S.; Papageorghiou, A.; Thilaganathan, B.OBJECTIVE: To determine the accuracy of dating twin pregnancies, of between 16 and 26 weeks' gestation, using singleton head circumference (HC) formulae. METHODS: This was a retrospective study of 269 singleton and 119 twin non-anomalous pregnancies conceived by in-vitro fertilization (IVF) with a known embryo transfer date. Fetal ultrasound biometry data for HC, obtained using different formulae, were compared with expected fetal HC size for gestation calculated from the date of conception. Similar comparisons were undertaken for femur length (FL) and for transverse cerebellar diameter. RESULTS: The mean differences in HC between observed ultrasound measurements and those expected from the IVF history were small (1-4 mm) and within the measurement error for both singletons and twins for all formulae. All measurements from the larger and the smaller twins straddled those of singletons, regardless of biometry and formula used. Negative skewing of FL measurements in the smaller twin suggests that fetal growth restriction may occur at this gestation and supports the practice of dating using the HC of the larger twin. CONCLUSIONS: Singleton pregnancy HC charts can be used to date reliably twin pregnancies. The data of the study also suggest that the HC of the larger twin is the most reliable measurement for use in datingItem Pregnancy outcome of monochorionic twins: does amnionicity matter?(Cambridge University Press, 2011) Dias, T.; Contro, E.; Thilaganathan, B.; Khan, H.; Zanardini, C.; Mahsud-Dornan, S.; Bhide, A.OBJECTIVE: To compare the fetal loss rate of monochorionic (MC) twin pregnancies according to their amnionicity. METHODS: A retrospective review of all MC pregnancy outcomes in a tertiary centre. Pregnancy outcomes were compared for monochorionic monoamniotic (MCMA) versus monochorionic diamniotic (MCDA) pregnancies. RESULTS: 29 MCMA and 117 MCDA twin pregnancies were identified. The overall fetal loss rate was significantly higher in MCMA (23/52, 44.2%) compared to MCDA pregnancies (28/233, 12%, Chi squared = 30.03, p < .001). Kaplan-Meier analysis showed that fetal survival rate in MCDA twinswere significantly higher than in MCMA twins (Log-rank Chi-squared = 27.9, p < .0005). Early pregnancy ultrasound identified the causes for these fetal losses in some MCMA twins. After exclusion of identifiable causes, the difference in fetal survival was not significant in the two groups (Log-rank chi-squared = 0.373, p = .54). CONCLUSION: The loss rate for MCMA twins is high and occurs mainly due to discordant congenital abnormality, conjoint twins or twin reversed arterial perfusion (TRAP) sequence. Although the fetal loss rate in MCDA is lower than in MCMA pregnancies, the majority of fetal loss in MCDA pregnancies cannot be predicted at the first scan at presentation. The data of this study questions the widespread policy of a difference in the scheduling of elective delivery for MCMA and MCDA twins.