Objective: To test the hypothesis that identical twins show no inter-twin differences in cardiovascular structure or physiology in fetal life unless there has been twin-twin transfusion syndrome. Design: Unselected prospective case-control observational study of fetoplacental haemodynamics including echocardiography at a median of 24 (16.7 to 32.3) weeks, with postnatal confirmation of congenital heart disease or normality. Setting: Fetal medicine unit. Patients: 136 women with monochorionic diamniotic twin pregnancies, of which 47 fetal twin pairs (35%) had twin-twin transfusion syndrome. Results: There were no haemodynamic differences between the bigger fetus (twin 1) and the smaller co-twin (twin 2) in uncomplicated monochorionic diamniotic pairs. In twin-twin transfusion syndrome, recipient fetuses had increased aortic and pulmonary velocities compared with their donor co-twins (mean (SD): 0.73 (0.23) m/s and 0.63 (0.14) m/s), respectively, v 0.53 (0.16) m/s and 0.48 (0.10) m/s in donor twins; p = 0.003 (aortic) and < 0.0001 (pulmonary)), and also in comparison with twin 1 and twin 2. The overall prevalence of congenital heart disease was increased above that in singletons (3.8% v 0.56%; 6.9% in twin-twin transfusion v 2.3% in uncomplicated monochorionic diamniotic twins), with inter-twin discordance for defects. The prevalence in recipient twins was 11.9% (p = 0.014 v uncomplicated control twins). Conclusions: Fetuses with an identical genome but no circulatory imbalance have similar cardiovascular physiology but discordant phenotypic expression of congenital heart disease. The high prevalence of congenital heart disease in monochorionic diamniotic twins merits detailed fetal echocardiography.
Objectives To document the duration of fetal cardiac time intervals in uncomplicated singleton pregnancies using a novel non-invasive fetal electrocardiography (fECG) system and to demonstrate this technique's ability to acquire recordings in twin and triplet pregnancies. Design Prospective cross sectional observational study.Setting Antenatal wards and clinics, day assessment unit and centre for fetal care at a tertiary referral hospital, London, UK. Population or Sample Three hundred and four singleton and multiple pregnancies, 15-41 weeks of gestation.Methods Using electrodes sited on the maternal abdomen, a fetal electrocardiography (fECG) system was developed and tested on 304 pregnant women from 15 to 41 weeks of gestation, of whom 241 were uncomplicated singletons, 58 had twin and 5 had triplet pregnancies. The composite abdominal signals were stored on a laptop computer and the fECG derived off-line using a digital signal processing technique. For singletons, linear regression was used to analyse PR, QRS, QT and QTc intervals, and construct time-specific reference ranges. Main outcome measure Duration of fECG time intervals as a function of gestational age. Success of signal separation in singleton, twin and triplet pregnancies. Results For singletons, a total of 250 recordings was obtained from 241 individuals with a signal separation success rate of 85% (213/250). Success rates were significantly poorer between 27 and 36 weeks of gestation (2 Â k m 2 , P < 0.0001), with 84% (31/37) of separation failures occurring during this period. P, Q, R and S waves were seen in all cases where fetal signals were separated and were used to generate fECG time interval reference ranges. In 22% (43/199) of analysed cases, no T waves were identified, 63% (27/43) of whom were 24 weeks of gestation. In twins and triplets, separate fetal signals were obtained in 78% (91/ 116) and 93% (14/15), respectively; P, Q, R and S waves were evident in all averaged fECGs, while T waves were identified in 59% (54/91) and 57% (8/14). Conclusions This study provides reference ranges with gestation for fECG intervals derived non-invasively from normal singleton pregnancies and demonstrates the feasibility of obtaining complete fECG recordings non-invasively across a wide gestational range in pregnancies of all pluralities. The fECG time intervals described will enable the identification of pathological fECG recordings from high risk pregnancies where fECG abnormalities are suspected.
The objective of this study was to determine the relationship between the type of placentation, vascular anatomy of the monochorionic (MC) placenta and the perinatal outcome of the surviving twin following a single intrauterine fetal death (IUFD). In this retrospective study, 92 twin pregnancies complicated by a single intrauterine death were identified from three tertiary referral centres [50 MC and 42 dichorionic (DC)]. Antenatal and neonatal data as well as information on the chorionicity, vascular anastomoses, and autopsy findings were also obtained. The percentage risk of IUFD (26 versus 2.4; P < 0.001), anaemia (51.4 versus 0; P < 0.001) and intracranial lesions at birth (46 versus 0; P < 0.001) was greater in MC than in DC twins. In MC twins without twin-twin transfusion syndrome (TTTS), perinatal mortality was higher in the group with superficial arterioarterial (AA)/venovenous (VV) channels than those with only multiple bidirectional arteriovenous (AV) anastomoses (12/15 versus 0/8; P < 0.001). However, in the TTTS pregnancies (n = 26), perinatal outcome of the surviving twin was dependent on whether the recipient (n = 16) or the donor twin (n = 10) died first. Incidence of IUFD (9/16 versus 0/10; P < 0.001), severe anaemia (7/7 versus 1/10; P < 0.001) and intracranial lesions at birth (6/7 versus 2/10; P < 0.001) was common in pregnancies where the recipient twin died first. In the TTTS group, unidirectional AV anastomotic channels were found in all but two placentae. In conclusion, this study suggests that the outcome of twin pregnancies complicated by IUFD is dependent on the type of vascular anastomoses and TTTS.
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