Intrauterine growth in multiple pregnancies in relation to fetal number, chorionicity and gestational age

Perinatal outcomes and growth discordance of triplet pregnancies based on chorionicity: a retrospective cohort study

BACKGROUND

The worldwide occurrence of triplet pregnancy is estimated to be 0.093%, with a natural incidence of approximately 1 in 8000. This study aims to analyze the neonatal health status and birth weight discordance (BWD) of triplets based on chorionicity from birth until discharge.

METHODS

This was a retrospective study. We reviewed a total of 136 triplet pregnancies at our tertiary hospital between January 1, 2001, and December 31, 2021. Maternal and neonatal outcomes, inter-triplet BWD, neonatal morbidity, and mortality were analyzed.

RESULTS

Among all cases, the rates of intrauterine death, neonatal death, and perinatal death were 10.29, 13.07, and 24.26%, respectively. Thirty-seven of the cases resulted in fetal loss, including 13 with fetal anomalies. The maternal complications and neonatal outcomes of the 99 triplet pregnancies without fetal loss were compared across different chorionicities, including a dichorionic (DC) group (41 cases), trichorionic (TC) group (37 cases), and monochorionic (MC) group (21 cases). Neonatal hypoproteinemia (P < 0.001), hyperbilirubinemia (P < 0.019), and anemia (P < 0.003) exhibited significant differences according to chorionicity, as did the distribution of BWD (P < 0.001). More than half of the cases in the DC and TC groups had a BWD < 15%, while those in the MC group had a BWD < 50% (47.6%). TC pregnancy decreased the risk of neonatal anemia (adjusted odds ratio [AOR] = 0.084) and need for blood transfusion therapy after birth (AOR = 0.119). In contrast, a BWD > 25% increased the risk of neonatal anemia (AOR = 10.135) and need for blood transfusion after birth (AOR = 7.127). TC pregnancy, MCDA or MCTA, and BWD > 25% increased neonatal hypoproteinemia, with AORs of 4.629, 5.123, and 5.343, respectively.

CONCLUSIONS

The BWD differed significantly according to chorionicity. Additionally, TC pregnancies reduced the risk of neonatal anemia and need for blood transfusion, but increased the risk of neonatal hypoproteinemia. In contrast, the BWD between the largest and smallest triplets increased the risk of neonatal anemia and the need for blood transfusion. TC pregnancy, MCDA or MCTA, and BWD > 25% increased the risks of neonatal hypoproteinemia. However, due to the limited number of triplet pregnancies, further exploration of the underlying mechanism is warranted.

The Association of Twin Chorionicity with Maternal Outcomes

OBJECTIVE

Our objective was to investigate the association between maternal outcomes and twin chorionicity in a large, contemporary obstetric population.

STUDY DESIGN

Retrospective cohort study was conducted at a single, large tertiary care center. Prenatal and inpatient records for all individuals with twin gestations were reviewed from 2000 to 2016. Patients with monoamniotic twins, higher-order multiples reduced to twins, multiple sets of twins in the study period, or undetermined chorionicity were excluded. Patients with monochorionic twins were compared with those with dichorionic twins. The co-primary outcomes were gestational diabetes mellitus and hypertensive disorders of pregnancy. Secondary outcomes included cesarean delivery, preterm delivery, postpartum hemorrhage, and other maternal outcomes. Bivariate and multivariate analyses were performed to assess associations of chorionicity with maternal outcomes.

RESULTS

Of the 2,979 patients eligible for inclusion, 2,627 (88.2%) had dichorionic twin gestations and 352 (11.8%) had monochorionic twin gestations. Patients with monochorionic twins were less likely to self-identify as non-Hispanic White and to have conceived via assisted reproductive technology but were more likely to be publicly insured, multiparous and have prenatal care with a maternal-fetal medicine provider. Neither gestational diabetes mellitus (6.8% monochorionic vs. 6.2% dichorionic, p = 0.74; adjusted odds ratio [OR] 1.06, 95% confidence interval (CI) 0.60-1.86) nor hypertensive disorders of pregnancy (21.9% monochorionic vs. 26.3% dichorionic, p = 0.09; adjusted OR 0.99, 95% CI, 0.71-1.38) differed by chorionicity. Of the secondary maternal outcomes, patients with monochorionic twins experienced a lower frequency of cesarean delivery (46.0 vs. 61.8%, p < 0.001), which persisted after multivariate analyses (adjusted OR 0.60, 95% CI 0.46-0.80). There were no differences in preterm delivery, preterm premature rupture of membranes, hemorrhage, hysterectomy, or intrahepatic cholestasis of pregnancy.

CONCLUSION

The odds of gestational diabetes mellitus and hypertensive disorders of pregnancy do not appear to differ by twin chorionicity.

KEY POINTS

· Hypertensive disorders of pregnancy do not differ by twin chorionicity.. · Gestational diabetes mellitus does not differ by twin chorionicity.. · Maternal outcomes are similar for individuals with monochorionic and dichorionic twin gestations..

Development of fetal growth charts in twins stratified by chorionicity and mode of conception: a retrospective cohort study in China

BACKGROUND

Twin pregnancies continue to increase worldwide; however, the current clinical prenatal evaluation for the intrauterine growth of twins still relies on the growth standards of singletons. We attempted to establish a set of fetal biometric references for Chinese twin pregnancies, stratified by chorionicity and conception mode as spontaneously conceived monochorionic diamniotic (SC-MCDA), spontaneously conceived dichorionic diamniotic (SC-DCDA), and assisted reproductive technology dichorionic diamniotic (ART-DCDA) twins.

METHODS

From 2016 to 2019, the ultrasonographic fetal biometric measurements were longitudinally collected in pregnant women, including fetal weight, biparietal diameter, head circumference, abdominal circumference, femur length, and humerus length. The linear mixed models were used to test the difference of growth patterns between groups, and the growth curve of each biometric parameter was modeled by a generalized additive model for location scale and shape.

RESULTS

A total of 929 twin pregnant women and 2019 singleton pregnant women, met the inclusion criteria. Among twin pregnancies, 148 were SC-MCDA, 215 were SC-DCDA, and 566 were ART-DCDA twins. Overall, SC-DCDA twins grew faster than SC-MCDA twins, while slower than ART-DCDA twins (all P < 0.05), and all of the three groups showed significant differences comparing with singletons, especially during the third trimester. Hence, the customized fetal growth charts of each fetal biometric parameter were, respectively, constructed for SC-MCDA, SC-DCDA, and ART-DCDA twins.

CONCLUSIONS

The fetal biometric trajectories demonstrated characteristic patterns according to chorionicity and conception mode. To fill the gap, we modeled fetal biometric parameters for Chinese SC-MCDA, SC-DCDA, and ART-DCDA twin pregnancies, hoping to provide a reference for the further establishment of fetal growth reference values for Chinese twin fetuses.

Predictive Accuracy of Singleton Versus Customized Twin Growth Chart for Adverse Perinatal Outcome: A Cohort Study

Background: Fetal growth of twins differs from singletons. The objective was to assess the fetal growth in twin gestations in relation to singleton charts and customized twin charts, respectively, followed by a comparison of the frequency of neonatal complications in small-for-gestational-age (SGA) twins. Methods: We performed an analysis of twin pregnancies with established chorionicity with particular emphasis on postnatal adverse outcomes in newborns classified as SGA. Neonatal birth weight was comparatively assessed using both singleton and twin growth charts with following percentile estimation. Using a statistical model, we established the prediction strength of neonatal complications in SGA twins for both methods. Results: The dataset included 322 twin pairs (247 cases of dichorionic and 75 cases of monochorionic diamniotic gestations). Utilization of twin-specific normograms was less likely to label twins as SGA—nevertheless, this diagnosis strongly correlated with risk of observing adverse outcomes. Using a chart dedicated for twin pregnancies predicted newborn complications in the SGA group with higher sensitivity and had better positive predictive value regarding postnatal morbidity. Conclusions: Estimating twin growth with customized charts provides better prognosis of undesirable neonatal events in the SGA group comparing to singleton nomograms and consequently might determine neonatal intensive care prenatal approach.

A cohort study of fetal growth in twin pregnancies by chorionicity: comparison with European and American standards

OBJECTIVE

To develop fetal growth standards for twin gestations by placental chorionicity in a Spanish population and compare them with European and American standards to estimate the suitability of their use in clinical practice.

STUDY DESIGN

This was a retrospective cohort study of 518 twin pregnancies, 435 dichorionic-diamniotic and 83 monochorionic-diamniotic, performed between January 2012 and December 2017. A total of 4,783 and 1,455 estimated fetal weights were considered from the 17^th to the 37^th week of gestation, using multilevel models, to build dichorionic-diamniotic and monochorionic-diamniotic standards, respectively. The percentages of small and large for gestational age were calculated as a model adjustment measure and adjustment to the studied data and the values provided by our model were compared against those of six European and American twin standards and three singleton standards. Correlation analyses between percentile predictions were performed using Cohen kappa coefficient. The predictive ability to detect small for gestational age was also provided by the sensitivity and positive predictive value.

RESULTS

We found slight differences between standards by chorionicity, being dichorionic-diamniotic percentiles slightly higher than monochorionic-diamniotic ones from the 17^th to 37^th weeks' gestation. For dichorionic-diamniotic cases, both our standard (9.8-8.2) and that of Grantz (8.2-10.5) showed good adjustments for the 10^th and 90^th percentiles while the other compared standards underestimated or overestimated them. For monochorionic-diamniotic cases, both our standard (10.2-8.5) and that of Shivkumar (11.4-6.8) had the most suitable adjustment. The correlation analysis between small and large for gestational age cases provided by standards, showed clear differences among them. Kappa's coefficient showed a substantial agreement between both Ananth (0.7) and Stirrup (0.69) dichorionic-diamniotic cases and our standard. There was also a substantial agreement between the Shivkumar (0.77) standard and our results for monochorionic-diamniotic cases. The correlation was moderate for all other comparisons.

CONCLUSIONS

Our model showed a good adjustment to the studied population. There are clear differences among small and large for gestational age cases provided by twin standards in our studied population. The twin growth standards depend on the population characteristics and model structure. We found the use of singleton standards for twin pregnancies inadequate.

Twin Pregnancies, Crown-rump Length and Birthweight Discordancy: The Influence of Chorionicity

OBJECTIVE

 The purpose of the present study was to analyze the influence of chorionicity in the biometric parameters crown-rump length (CRL), birthweight (BW), crown-rump length discordancy (CRLD) and birthweight discordancy (BWD), determine the correlation between these latter two in cases of intertwin discordancy, and to analyze the influence of chronicity in the presence of these discordancies with clinical relevance (> 10% and > 15%, respectively).

METHODS

 The present study was a retrospective study based on the twin pregnancy database of the Centro Hospitalar S. João (2010-2015), including 486 fetuses among 66 monochorionic (MC) and 177 dichorionic gestations (DC). The inclusion criteria were multiple pregnancies with 2 fetuses and healthy twin gestations. The exclusion criteria were trichorionic gestations and pregnancies with inconclusive chorionicity, multiple pregnancy with ≥ 3 fetuses and pathological twin gestations.

RESULTS

 No statistically significant difference was found in BW (p = 0.09) and in its discordancy (p = 0.06) nor in CRL (p = 0.48) and its discordancy (p = 0.74) between MCs and DCs. Crown-rump length discordancy and birthweight discordancy were correlated by the regression line "BWD = 0.8864 x CRLD + 0.0743," with r²  = 0.1599. Crown-rump length discordancy > 10% was found in 7.58% of monochorionic and in 13.56% of dichorionic twins. Birthweight discordancy > 15% was detected in 16.67% of monochorionic and in 31.64% of dichorionic twins.

CONCLUSION

 No statistically significant influence of chorionicity was identified in both birthweight and birthweight discordancy, as in crown-rump length and crown-rump length discordancy. Birthweight discordancy was correlated to crown-rump length discordancy in 20% of cases.

Umbilical Cord Hepcidin Concentrations Are Positively Associated with the Variance in Iron Status among Multiple Birth Neonates

Background

Hepcidin is a systemic regulator of iron homeostasis. Little is known about the relative role of maternal compared with cord hepcidin on neonatal iron homeostasis.

Objective

This study was undertaken to evaluate inter- and intrauterine variance in neonatal iron status, vitamin B-12, folate, and inflammatory markers in a cohort of twins (n = 50), triplets (n = 14), and quadruplets (n = 1) born to 65 women.

Methods

Umbilical cord blood was obtained from 144 neonates born at 34.8 ± 2.7 wk of gestation with a mean birth weight of 2236 ± 551 g (means ± SDs). Cord hemoglobin and cord serum measures of ferritin (SF), soluble transferrin receptor (sTfR), hepcidin, erythropoietin (EPO), iron, vitamin B-12, folate, interleukin 6, and C-reactive protein were evaluated.

Results

Intraclass correlation coefficient (ICC) analyses were used to examine inter- and intrauterine variance in neonatal iron indicators. A greater variability in cord hepcidin (ICC = 0.39) was found between siblings. Cord hepcidin had the greatest association with cord iron indicators because cord hepcidin alone captured 63.8%, 48.4%, 44.4%, and 31.3% of the intrauterine variance in cord hemoglobin, SF, sTfR, and EPO, respectively, whereas maternal hepcidin had no effect on cord iron indicators. Significantly greater differences in cord SF (P = 0.03), sTfR (P = 0.03), hepcidin (P = 0.0003), and EPO (P = 0.03) were found between di- and trichorionic siblings than between monochorionic siblings. In contrast, cord folate (ICC = 0.79) and vitamin B-12 (ICC = 0.74) exhibited a greater variability between unrelated neonates.

Conclusions

In summary, fetally derived hepcidin might have more control on intrauterine variance in iron indicators than maternal hepcidin and appears to be capable of regulating fetal iron status independently of maternal hepcidin. The use of a multiple-birth model provides a unique way to identify factors that may contribute to placental nutrient transport and iron stores at birth.

Evaluation of placental vascularization indices in monochorionic diamniotic and dichorionic diamniotic twin pregnancies

OBJECTIVES

We aimed to investigate and compare placental vascularization indices between monochorionic-diamniotic, dichorionic-diamniotic normal twin pregnancies, and normal singular pregnancies. We hypothesized that there is correlation between placental three-dimensional power Doppler vascularization indices and birth weight in case of twin pregnancies, and that normal singular pregnancies have higher placental vascularization indices than normal twin pregnancies.

STUDY DESIGN

Placental three-dimensional power Doppler vascularization indices, such as vascularization index, flow index, and vascularization-flow index were measured in monochorionic-diamniotic (N = 15) and dichorionic-diamniotic (N = 36) normal twin pregnancies, and in normal singular (N = 109) pregnancies. Correlations were analyzed between vascularization indices, and birth weight, APGAR score, umbilical pH, umbilical venous bicarbonate, lactate, and base excess.

RESULTS

Vascularization indices and birth weight were significantly (p < 0.01) higher in normal singular gestations (vascularization index = 10.36, flow index = 46.08, vascularization-flow index = 4.08, average birth weight = 3377 g at 38.2 weeks average gestational age) compared to monochorionic-diamniotic and dichorionic-diamniotic normal twin pregnancies. No significant differences were found in vascularization indices between monochorionic-diamniotic and dichorionic-diamniotic normal twins. There were no significant differences in APGAR score, umbilical pH, umbilical venous bicarbonate, lactate, and base excess between groups examined (p < 0.01). We found strong linear correlations between placental vascularization indices and birth weight in both twin groups.

CONCLUSION

Placental three-dimensional power Doppler vascularization indices seem appropriate for predicting birth weight in monochorionic-diamniotic and dichorionic-diamniotic normal twin pregnancies. Our pilot study revealed reference values for vascularization indices in case of twin pregnancies examined.

Genetic and Environmental Influences on Fetal Growth Vary during Sensitive Periods in Pregnancy

Aberrant fetal growth is associated with morbidities and mortality during childhood and adult life. Although genetic and environmental factors are known to influence in utero growth, their relative contributions over pregnancy is unknown. We estimated, across gestation, the genetic heritability, contribution of shared environment, and genetic correlations of fetal growth measures (abdominal circumference (AC), humerus length (HL), femur length (FL), and estimated fetal weight (EFW)) in a prospective cohort of dichorionic twin gestations recruited through the NICHD Fetal Growth Studies. Structural equation models were fit at the end of first trimester, during mid-gestation, late second trimester, and third trimester of pregnancy. The contribution of fetal genetics on fetal size increased with gestational age, peaking in late second trimester (AC = 53%, HL = 57%, FL = 72%, EFW = 71%; p < 0.05). In contrast, shared environment explained most of phenotypic variations in fetal growth in the first trimester (AC = 50%, HL = 54%, FL = 47%, EFW = 54%; p < 0.05), suggesting that the first trimester presents an intervention opportunity for a more optimal early fetal growth. Genetic correlations between growth traits (range 0.34–1.00; p < 0.05) were strongest at the end of first trimester and declined with gestation, suggesting that different fetal growth measures are more likely to be influenced by the same genes in early pregnancy.

Placental Histopathology Differences and Neonatal Outcome in Dichorionic-Diamniotic as Compared to Monochorionic-Diamniotic Twin Pregnancies

OBJECTIVE

We aimed to compare the differences in placental histopathology lesions and pregnancy outcome in dichorionic-diamniotic (DCDA) versus uncomplicated monochorionic-diamniotic (MCDA) twin gestations.

STUDY DESIGN

Maternal characteristics, neonatal outcome, and placental histopathology reports of all twin deliveries between 24 and 41 weeks were reviewed. Excluded were pregnancies complicated by twin-to-twin transfusion syndrome, twin anemia-polycythemia sequence, selective intrauterine growth restriction, placenta previa, intrauterine fetal death, and malformation. Placental lesions were classified to maternal/fetal vascular malperfusion lesions. Umbilical cord abnormalities included hypo-/hypercoiling and abnormal insertion. Composite adverse neonatal outcome was defined as 1 or more early complications. Small for gestational age (SGA) was defined as birth weight ≤10th percentile.

RESULTS

The DCDA group (n = 362) was characterized by higher rates of assisted reproductive techniques ( P < .001) and nulliparity ( P = .03) as compared to the MCDA group (n = 65). Gestational age at delivery was similar between groups. Placental maternal vascular malperfusion lesions were more common in placentas from DCDA group (38.2% vs 23.1%; P = .016), while fetal vascular malperfusion lesions and abnormal cord insertion were more common in placentas from MCDA group ( P = .027; P< .001). The SGA and composite adverse neonatal outcome were more common in the MCDA group ( P = .031 and P = .038, respectively). By multivariate regression analysis, composite adverse neonatal outcome was found to be independently associated with the MCDA group, adjusted odds ratio (aOR) = 1.2, 95% confidence interval (CI) = 1.04 to 1.89, P = .041, and with placental fetal malperfusion lesions aOR = 1.3, 95% CI = 1.1 to 2.09, P = .038.

CONCLUSION

Placental pathology differs between MCDA and DCDA twin pregnancies. Adverse neonatal outcome in uncomplicated MCDA twins, as compared to DCDA twins, could be related to increased placental fetal malperfusion lesions and abnormal cord insertion.

MODELLING THE RISK FACTORS FOR BIRTH WEIGHT IN TWIN GESTATIONS: A QUANTILE REGRESSION APPROACH

Birth weight is used as a proxy for the general health condition of newborns. Low birth weight leads to adverse events and its effects on child growth are both short- and long-term. Low birth weight babies are more common in twin gestations. The aim of this study was to assess the effects of maternal and socio-demographic risk factors at various quantiles of the birth weight distribution for twin gestations using quantile regression, a robust semi-parametric technique. Birth records of multiple pregnancies from between 1991 and 2005 were identified retrospectively from the birth registry of the Christian Medical College and hospitals in Vellore, India. A total of 1304 twin pregnancies were included in the analysis. Demographic and clinical characteristics of the mothers were analysed. The mean gestational age of the twins was 36 weeks with 51% having preterm labour. As expected, the examined risk factors showed different effects at different parts of the birth weight distribution. Gestational age, chroniocity, gravida and child's sex had significant effects in all quantiles. Interestingly, mother's age had no significant effect at any part of the birth weight distribution, but both maternal and paternal education had huge impacts in the lower quantiles (10th and 25th), which were underestimated by the ordinary least squares (OLS) estimates. The study shows that quantile regression is a useful method for risk factor analysis and the exploration of the differential effects of covariates on an outcome, and exposes how OLS estimates underestimate and overestimate the effects of risk factors at different parts of the birth weight distribution.

Ultrasound estimation of birth weight in twin pregnancy: comparison of biometry algorithms in the STORK multiple pregnancy cohort

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 twin pregnancies.

METHODS

This was a retrospective cohort study including both singleton and twin pregnancies. Routine biometry was recorded and estimated fetal weight (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 in twin 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 twin pregnancies. 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 twin pregnancies, respectively. When t e 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.

Intrauterine environment and cognitive development in young twins

Intrauterine factors important for cognitive development, such as birth weight, chorionicity and umbilical cord characteristics were investigated. A total of 663 twin pairs completed the Wechsler Intelligence Scale for Children-Revised and scores were available for Performance, Verbal and Total Intelligence Quotient (IQ). The intrauterine factors examined were birth weight, placental weight and morphology, cord knots, cord length and cord insertion. IQ scores for the varying levels of the intrauterine markers adjusting for gender and gestational age were calculated. The heritability of IQ and the association between IQ and intrauterine environment were examined. Twins with lower birth weight and cord knots had lower IQ scores. The aetiology of IQ is largely distinct from that of birth weight and cord knots, and non-shared environment may influence the observed relationships.

Associations for birthweight of twin pairs in south India

AIM

The aim of this study was to determine the distribution and associations of birthweight in twin pairs among a population of pregnant women in south India.

MATERIAL AND METHODS

This was a retrospective case record analysis of 705 twin pair pregnancies during the period 2008-2012. Associations of birthweight with maternal age, parity, pregnancy-induced hypertension (PIH), gestational diabetes, obesity, chorionicity and sex of the twin pairs was explored using bivariate and multivariate analysis.

RESULTS

The median birthweight (4250 g, interquartile range 3530-4810) of dichorionic twins was significantly higher (P < 0.0001) than monochorionic twins (3880 g, interquartile range 3000-4380). Birthweight was associated with chorionicity (t = 4.04, P < 0.001), obesity (t = 2.44, P = 0.03), nulliparity (t = -2.87, P = 0.004), and PIH (t = -2.11, P = 0.04) in a multivariate linear regression model. Birthweights did not differ significantly between female-male and female-female pairs (t = 0.11, P = 0.81), female-male and male-male pairs (t = -0.62, P = 0.54) or female-female and male-male pairs (t = -0.78, P = 0.43) in a multivariate linear regression model. The highest birthweight of the twin pair did not differ significantly (t = 1.27, P = 0.21) by sex of the twin.

CONCLUSIONS

Birthweight of twins was significantly associated with chorionicity, obesity, PIH and nulliparity in this population. A potential masculinization effect was not found as the total birthweights did not differ significantly by sex of the twin pairs.

Ultrasound in twins: dichorionic and monochorionic

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

Perinatal death of triplet pregnancies by chorionicity

OBJECTIVE

The purpose of this study was to evaluate the perinatal risk of death by chorionicity at >22 weeks of gestation of triplet pregnancies.

STUDY DESIGN

In a retrospective cohort study, the perinatal data were collected from triplet pregnancies in Japanese perinatal care centers between 1999 and 2009. We included maternal characteristics and examined the following factors: prenatal interventions, pregnancy outcome, and neonatal outcome. The association between fetal or neonatal death of triplets and chorionicity was evaluated by logistic regression analysis.

RESULTS

After the exclusion of 253 cases, the study group comprised 701 cases: 507 trichorionic triamniotic (TT) triplet pregnancies, 144 diamniotic triamniotic (DT) triplet pregnancies, and 50 monochorionic triamniotic (MT) triplet pregnancies. The mortality rate (fetal death at >22 weeks of gestation; neonatal death) in triplets was 2.6% and included 2.1% of TT triplet pregnancies, 3.2% of DT triplet pregnancies, and 5.3% of MT triplet pregnancies. No significant risk of death was identified in DT triplet pregnancies; however, MT triplet pregnancies had a 2.6-fold greater risk (adjusted odds ratio, 2.60; 95% confidence interval, 1.17-5.76; P = .019) compared with TT triplet pregnancies. Prophylactic cervical cerclage did not reduce the perinatal mortality rate at >22 weeks of gestation in triplets.

CONCLUSION

The risk of death for MT triplet pregnancies is significantly higher than that of TT triplet pregnancies; however, the risk of death for DT triplet pregnancies is not.

Size at birth and adult fat mass in twin sheep are determined in early gestation

Size at birth is related to adult health outcomes. Twins are born smaller than singletons; this has been assumed to be secondary to limited nutrient supply in late gestation.We hypothesised that growth trajectory in twins, and the adult consequences of being conceived a twin, are determined in early gestation. Twin pregnancies in sheep were randomised to reduction of one twin on day 42 of a 148 day pregnancy by intra-thoracic KCl (Reductions, n =46) or a sham procedure (Twins, n =22). Singleton-bearing ewes also underwent a sham procedure (n =27). Ewes lambed spontaneously. Linear measures of size at birth were similar in Twins and Reductions, and significantly less than in Singletons. Birthweight was lower in Twins and Reductions than in Singletons, and less in Twins than in Reductions (means (SEM): Singletons, liveborn n =23: 6.59 (0.17) kg; Twins, liveborn n =36: 5.23 (0.16) kg; Reductions, liveborn n =27: 5.76 (0.15) kg; all comparisons P <0.05). Reductions grew most rapidly between birth and weaning (Singletons, 20.0 (0.4) g kg⁻¹ day⁻¹; Twins, 20.0 (0.3) g kg⁻¹ day⁻¹; Reductions, 21.0 (0.3) g kg⁻¹ day⁻¹, P <0.05) and were of similar weight as Singletons by weaning; Twins remained smaller by weaning but grew most rapidly thereafter (Singletons, 1.6 (0.1) g kg⁻¹ day⁻¹; Twins, 2.1 (0.1) g kg⁻¹ day⁻¹; Reductions, 1.6 (0.1) g kg⁻¹ day⁻¹, P <0.01), so that all groups had similar weight at 2 years. However, Twins and Reductions had greater percentage fat mass than Singletons at 2 years (Singletons, 11.1 (1.1)%; Twins, 14.8 (1.2)%; Reductions, 15.5 (1.1)%, P <0.05). Thus, in twins, fetal growth trajectory, linear size at birth and adult fat mass are largely determined in early gestation. If this is also true in humans, there are important implications for interventions aimed at optimising fetal growth and pregnancy outcome.

Epigenetic modifications may play a role in the developmental consequences of early life events

Many aspects of postnatal development are influenced by events before birth, including cognitive and language development. An adverse intrauterine environment, for example secondary to poor maternal nutritional status, multiple pregnancy, or late preterm birth, is associated with increased risks of delayed or impaired childhood development and altered physiology in adulthood that may predispose to increased risk of adult disease. Maternal periconceptional undernutrition and twin conception can both result in late preterm birth, but it is less clear whether cases of late preterm birth not following a recognized early pregnancy event may still have their origin in the periconceptional period. Thus, the very earliest periods of pregnancy, and perhaps even the pre-pregnancy period, may be an important period determining the developmental trajectory of the fetus, and thus both pregnancy and later health outcomes. Profound epigenetic modifications to the genome occur in the early embryo as a normal part of development. Recent evidence suggests that environmental signals acting during early development may also result in epigenetic changes which may play a role in mediating the association between early life exposures and later phenotype.

Análise de tendências das taxas de mortalidade infantil e de seus fatores de risco na cidade de Porto Alegre, Rio Grande do Sul, Brasil, no período de 1996 a 2008

Objetiva-se determinar as tendências de mortalidade infantil e de seus fatores de risco em Porto Alegre. Este é um estudo baseado nas informações do registro de nascidos vivos e de óbitos infantis no período de 1996-2008. Foi analisada a tendência temporal das taxas de mortalidade infantil (TMI) e de seus componentes, de acordo com a escolaridade materna, o número de consultas de pré-natal, idade materna, número de filhos vivos e mortos, sexo do recém-nascido, o tipo de parto, a idade gestacional, o peso de nascimento e o tipo de hospital. Foi utilizada a regressão sequencial de Poisson para estimar a influência da condição socioeconômica e os demais fatores de risco. A TMI decaiu entre os nascidos de mães com escolaridade inferior a 11 anos. Entre os nascidos de mães com 12 ou mais anos de escolaridade, não houve alterações significativas. A condição socioeconômica materna foi o fator que mais se associou à redução da mortalidade infantil. Contudo, a tendência de redução não atingiu todo o potencial devido ao aumento do baixo peso ao nascer.