Browsing by Author "Thilaganathan, B."

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Birth weight differences at term are explained by placental dysfunction, but not by maternal ethnicity
(John Wiley & Sons, 2018) Morales-Roselló, J.; Dias, T.; Khalil, A.; Fornes-Ferrer, V.; Ciammella, R.; Gimenez Roca, L.; Perales-Marín, A.; Thilaganathan, B.
OBJECTIVE: The main aim of this study was to investigate the influence of ethnicity, fetal gender and placental dysfunction on birth weight (BW) in term fetuses of South Asian and Caucasian origin. METHODS: This was a retrospective study of 627 term pregnancies assessed in two public tertiary hospitals in Spain and Sri Lanka. All fetuses underwent a scan and Doppler examination within two weeks of delivery. The influences of fetal gender, ethnicity, gestational age (GA) at delivery, cerebroplacental ratio (CPR), maternal age, height, weight and parity on BW were evaluated by multivariable regression analysis. RESULTS: Fetuses born in Sri Lanka were smaller than those born in Spain (mean BW= 3026g±449g versus 3295g±444g, p<0.001). Multivariable regression analysis demonstrated that GA at delivery, maternal weight, CPR, maternal height and fetal gender (estimates=0.168, p<0.001; 0.006, p<0.001; 0.092, p=0.003; 0.009, p=0.002; 0.081, p=0.01) were significantly associated with BW. Conversely, no significant association was noted with maternal ethnicity, age and parity (estimates= -0.010, p=0.831; 0.005, p=0.127; 0.035, p=0.086). The findings were unchanged when the analysis was repeated using IG21 EFW instead of BW centile (-0.175, p=0.170; 0.321, p<0.001). CONCLUSIONS: Fetal BW variation at term is less dependent on ethnic origin and better explained by placental dysfunction.
Cord entanglement and perinatal outcome in monoamniotic twin pregnancies
(Wiley, 2010) Dias, T.; Mahsud-Dornan, S.; Bhide, A.; Papageorghiou, A. T.; Thilaganathan, B.
OBJECTIVES: To assess the prevalence of cord entanglement and perinatal outcome in a large series of monoamniotic twin pregnancies and to review the recent literature on similar published large series. METHODS: Prospective observational study of all prenatally detected cases of monoamniotic twin pregnancies during an 8-year period in a tertiary fetal medicine unit. A Medline database review for publications since 2000 containing five or more cases of monoamniotic pregnancies that showed data on cord entanglement and perinatal outcome was also undertaken. RESULTS: A total of 32 monoamniotic pregnancies were diagnosed during the study period, including three conjoined twins, seven pregnancies with twin reversed arterial perfusion (TRAP) syndrome, three surgical pregnancy interruptions for discordant fetal abnormality and one miscarriage before 16 weeks' gestation. The remaining 18 monoamniotic pregnancies were included in the study analysis. All monoamniotic pregnancies were complicated with antenatal cord entanglement diagnosed by B-mode and color Doppler ultrasound. There were 34 live births and a double intrauterine death diagnosed at 19 + 2 weeks' gestation. There were two late neonatal deaths, one from congenital complete heart block and the other after surgery for transposition of the great arteries. The overall perinatal loss rate was 11.1% after 16 weeks and 5.9% after 20 weeks' gestation. The cumulative rates of cord entanglement and perinatal mortality in the reviewed literature were 74% and 21%, respectively. CONCLUSIONS: Umbilical cord entanglement is present in all monoamniotic twins when it is systematically evaluated by ultrasound and color Doppler. Perinatal mortality in monoamniotic twins is mainly a consequence of conjoined twins, TRAP, discordant anomaly and spontaneous miscarriage before 20 weeks' gestation. Expectantly managed monoamniotic twins after 20 weeks have a very good prognosis despite the finding of cord entanglement. The practice of elective very preterm delivery or other interventions to prevent cord accidents in monoamniotic twins should be re-evaluated.
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.
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 examination
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.
Early pregnancy growth and pregnancy outcome in twin pregnancies
(Sri Lanka Medical Association, 2010) Dias, T.; Bhide, A.; Thilaganathan, B.
OBJECTIVES: The objective of this study was to determine the association of crown-rump length (CRL) discrepancy in monochorionic and dichorionic twins with subsequent pregnancy outcomes. METHOD: A retrospective analytical study was performed among 660 twin pregnancies over 12 years in one fetal medicine tertiary referral center in the United Kingdom. A literature search was performed to identify all reports in the English language literature in this topic between 1998 and 2009. RESULTS: Five hundred and six dichorionic and 154 monochorionic twin pregnancies were studied. Median percentage CRL discordance in monochorionic and dichorionic pregnancies was not different (3.9 +/- 8.34, range 0-59 and 3.2 +/- 5.65 range 0-37.5, respectively, p = 0.225). Single or double fetal loss was higher in monochorionic twins than the dichorionic twins. Loss rate was 17.53% (27) and 3.95% (20) respectively (p = < .0001). CRL disparity and birth weight discordancy showed statistically significant correlation (Spearman's rho, p = 0.040). Statistically significant correlation was seen between percentage CRL disparity and pregnancy loss rate (p = 0.008). However, the sensitivity of this CRL discrepancy to detect subsequent fetal loss or birth weight discordance is poor. INTERPRETATION: CRL discrepancy is independent of chorionicity in twins. CRL discrepancy is correlated to subsequent pregnancy loss and birth weight discordance, but the clinical utility of this observation is limited. The difference in twin CRL at 11-14 weeks is likely to represent physiological variation in a majority of cases.
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 avialable
First-trimester ultrasound dating of twin pregnancy: are singleton charts reliable?
(Wiley, 2010) Dias, T.; Mahsud-Dornan, S.; Thilaganathan, B.; Papageorghiou, A. T.; Bhide, A.
OBJECTIVE: The aim of this study was to assess the performance of validated singleton crown-rump length (CRL) formulae in dating twin pregnancies at 11-14 weeks of gestation. DESIGN: Retrospective cohort study. SETTING: Fetal medicine unit of a London teaching hospital. SAMPLE: Three hundred and eighty-four pregnancies with known dates of conception. METHODS: Retrospective analysis of 266 singletons and 118 twin pregnancies conceived by in vitro fertilisation (IVF), with a known date of conception. The gestation calculated from the date of conception was compared with the expected gestation from fetal size using a number of different CRL formulae. MAIN OUTCOME MEASURES: Difference in gestational age computed from fetal size (CRL) of the bigger and smaller fetus in twin pregnancies and singleton pregnancies using three formulae. RESULTS: Two of the three studied CRL formulae systematically underestimated the mean gestational age and size of singleton IVF pregnancies (Robinson formula: gestation = 1.4 days, size = 2.7 mm). Twin CRL measurements straddled those of singletons, regardless of the CRL formula used (Robinson formula: larger twin gestation = 2.4 days, size = 4.7 mm; smaller twin gestation = 0.8 days, size = 1.7 mm). These underestimates in gestation and size for IVF singleton and twin pregnancies are well within the known limits of accuracy of first = trimester ultrasound measurements, and are of limited clinical significance. CONCLUSIONS: Currently available CRL charts underestimate both the age and size of IVF singleton pregnancies by a clinically insignificant amount. This difference is similar for twin pregnancies, suggesting that singleton CRL charts can be used to date twin pregnancies accurately.
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.
The influence of chorionicity and gestational age at single fetal loss on the risk of preterm birth in twin pregnancies: analysis of the STORK multiple pregnancy cohort
(Wiley, 2017) D'Antonio, F.; Thilaganathan, B.; Dias, T.; Khalil, A.; Southwest Thames Obstetric Research Collaborative (STORK)
BACKGROUND: Single intrauterine death (sIUD) in twin pregnancies is associated with a significant risk of co-twin demise and pretermbirth (PTB), especially in monochorionic (MC) twins. However, it is yet to be established whether the gestational age at loss may influence the pregnancy outcome. The aim of this study was to explore the risk of PTB according to the gestational age at the diagnosis of sIUD. METHODS: A cohort study of all twin pregnancies from a large regional network of 9 hospitals over a ten-year period. Ultrasound data was matched to hospital delivery records and a mandatory national register for perinatal losses (CMACE). Cases with double fetal loss at the time of the scan were not included in the analysis. The cumulative rates of PTB before 34, 32 and 28 weeks of gestation was assessed in pregnancies which did vs those which did not experience sIUD. The risk of PTB was stratified according to the gestationalage at the diagnosis of sIUD. RESULTS: The analysis included 3013 twin gestations (2469 DC and 544 MC) . Median gestational age at birth was lower in the pregnancies complicated by sIUD compared to those which were not (32.0 weeks, IQR 29.0-34.3 vs 36.7 weeks, IQR 35.0-37.6; p < 0.001) and this difference persisted when stratifying the analysis according to chorionicity (p < 0.0001 for both MC and DC pregnancies). The risk of PTB before 34 weeks (RR: 4.3, 95% CI 3.5-5.2), before 32 weeks (RR: 6.1, 95% CI 4.6-8.1) and before 28 weeks (RR: 12.40, 95% CI 6.9-22.2) was higher in pregnancies complicated by a sIUD compared to those which did not experience any fetal loss. This association was observed both in MC and DC twin gestations. When compared to DC pregnancies, MC twins affected by sIUD were not at significantly increased risk of PTB either before 34, 32 or 28 weeks of gestation. The risk of PTB before 34 weeks of gestation was higher when the sIUD occurred at a later gestational age (Chi-square test for trend, p < 0.001). CONCLUSION: Twin pregnancies complicated by sIUD, regardless of the chorionicity, have a significantly higher risk of PTB before 34, 32 and 28 weeks of gestation. The risk of PTB before 34 weeks of gestation was higher when the sIUD occurred in the second half of the pregnancy. Large prospective multicenter studies with shared protocols for prenatal management are needed to ascertain the actual risk of spontaneous PTB in twin pregnancies affected by sIUD.
Is first-trimester crown-rump length associated with birthweight?
(Wiley, 2012) Dias, T.; Thilaganathan, B.
No Abstract avialable
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.
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.
The Role of ultrasound in obstetrics
(Sri Lanka College of Obstetricians and Gynaecologists, 2009) Dias, T.; Thilaganathan, B.
No Abstract Available
Screening for pre-eclampsia by using changes in uterine artery Doppler indices with advancing gestation
(Wiley, 2012) Napolitano, R.; Melchiorre, K.; Arcangeli, T.; Dias, T.; Bhide, A.; Thilaganathan, B.
OBJECTIVE: The aim of the study was to assess the relationship of changes in uterine artery (UtA) Doppler pulsatility indices (PI) between first and second trimesters and the subsequent development of pre-eclampsia. METHODS: A retrospective study of singleton pregnancies undergoing both first and second trimesters UtA Doppler screening between 2002 and 2009 was conducted. Multiples of median of UtA Doppler PI were used for developing indices describing UtA changes between the two trimesters. Receiver-operating characteristics curves (ROC) were calculated for multiple comparisons. RESULTS:Three thousand five hundred sixty women had UtA Doppler screening in the first and second trimesters. Eleven women were excluded because of termination of pregnancy before 24 weeks. Out of the 3549 women recruited, 126 developed Pre-eclampsia (PE; 22 early PE delivered <34 weeks and 41 preterm PE delivered <37 weeks). The best index for predicting pre-eclampsia was the difference between the mean second trimester and mean first trimester UtA PI (areas under the ROC for early PE and preterm PE of 0.851 and 0.786, respectively). CONCLUSION:Changes of UtA resistance between the first and second trimesters can be calculated as the difference between UtA PI at these gestations. The data of this study demonstrate that the difference in mean PI is the best index in predicting early PE and preterm PE.
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 dating
Systematic labeling of twin pregnancies on ultrasound
(Wiley, 2011) Dias, T.; Ladd, S.; Mahsud-Dornan, S.; Bhide, A.; Papageorghiou, A. T.; Thilaganathan, B.
OBJECTIVE: Correct labeling of twin fetuses is needed for consistency in assigning and interpreting longitudinal scan and prenatal screening/diagnostic results. The aim of this study was to describe a standard method of twin labeling in the first trimester of pregnancy and to assess the robustness of such a technique in predicting the presenting twin in subsequent scans and at delivery. METHODS: This was a retrospective first-trimester study of all twin pregnancies assessed by ultrasonography at our center between 2000 and 2010. The fetus contained in the gestational sac closer to the maternal cervix was designated as Twin 1 and the relative orientation of the fetuses to each other was then defined as either lateral (left/right) or vertical (top/bottom). In discordant-sex twins, their sex and presenting order on the final scan prior to delivery were documented and compared with the sex and birth order at delivery. RESULTS: A total of 416 twin pregnancies were seen during the study period. At the 11-14-week scan 90.9% of twins were in lateral orientation while the remainder were oriented vertically. None of the vertically oriented twin pairs but 32 (8.5%) of the laterally oriented twin pairs changed their presenting order between the first and the last ultrasound scan prior to delivery. There were 108 discordant-sex twins scanned in the third trimester, of which the birth order changed in 20.3% that were delivered by Cesarean section and in 5.9% of those delivered vaginally. CONCLUSION: The study demonstrates that antenatal labeling of twins according to laterality or vertical orientation is reliable. The technique ensures continuity of biometric assessment from serial scans at each visit, and as such should be adopted as the preferred method of twin labeling. Furthermore, the use of orientation for antenatal labeling of twins rather than assignment of a number based on proximity to the cervix, precludes any misconception regarding which twin will be born first and ensures that parents and pediatricians are aware of the significant likelihood of a peripartum switch
Twin pregnancy chorionicity determination in a tertiary care setting
(Sri Lanka Medical Association, 2013) Dias, T.; Weerasinghe, A.; Amarathunga, P.; de Silva, C.; Thilaganathan, B.
Ultrasound determination of chorionicity is most reliable before 14 weeks and subsequently reduces in accuracy with advancing gestation. The aim of this study was to evaluate the accuracy of chorionicity determination in a birth cohort of twin pregnancies. Antenatal ultrasound determination of chorionicity in twin pregnancy was undertaken at sub optimal period of gestation in over two thirds of twin pregnancies. Even in the first trimester of pregnancy, the accuracy of chorionicity determination was lower than previously reported.
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.
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 Ltd