Increased perinatal mortality and morbidity in monochorionic versus dichorionic twin pregnancies: clinical implications of a large Dutch cohort study

Intrapartum management of twin pregnancies: are uncomplicated monochorionic pregnancies more at risk of complications than dichorionic pregnancies?

OBJECTIVE

To analyze mode of delivery and neonatal morbidity according to chorionicity in a hospital birth center with a policy of vaginal delivery for twins.

STUDY DESIGN

Retrospective analysis over a 13-year period.

SETTING

Department of Obstetrics, University Hospital, Lille, France.

POPULATION

In all, 1009 twin pregnancies were included, divided into 171 uncomplicated monochorionic pregnancies (17%) and 838 dichorionic pregnancies (83%).

METHODS

We compared the monochorionic and the dichorionic populations.

MAIN OUTCOME MEASURES

Rate of cesarean section and neonatal outcome (umbilical artery pH, Apgar score and neonatal complications).

RESULTS

The rate of cesarean sections was 45.7% with no difference found based on chorionicity. The reasons for elective cesarean section were mainly noncephalic presentation, which was more frequent in dichorionic than in monochorionic (48.8% vs. 37.2%, p = 0.025) pregnancies. Birthweight was lower in monochorionic twins (2249 ± 469 g vs. 2329 ± 478 g, p = 0.045). The rate of umbilical artery cord blood values with a pH < 7.10 was similar in monochorionic and dichorionic pregnancies. There was no difference in neonatal complications between the two groups.

CONCLUSION

Monochorionic and dichorionic twin pregnancies had similar delivery outcomes. The neonatal outcome for twin 2 was not different between monochorionic and dichorionic pregnancies. Vaginal birth could be offered to women with twin pregnancies regardless of chorionicity.

Neonatal and infant outcomes in twin gestations with preterm premature rupture of membranes at 24-31 weeks of gestation

OBJECTIVE

To describe the perinatal and infant and early childhood morbidity associated with preterm premature rupture of membranes (PROM) in a cohort of twin pregnancies evaluated prospectively with neonatal follow-up to 2 years of age.

METHODS

This was a secondary analysis of a randomized controlled trial of magnesium sulfate for prevention of cerebral palsy. Inclusion criteria were twin gestation with preterm PROM diagnosed between 24 0/7 and 31 6/7 weeks of gestation and planned expectant management. Latency (time from membrane rupture to delivery) and perinatal outcomes were evaluated by gestational age at membrane rupture. Long-term neonatal outcomes were also analyzed.

RESULTS

Among 151 women who met inclusion criteria, the median gestational age at preterm PROM was 28.1 weeks (range 24.1-31.6 weeks). Approximately one-third of women achieved a latency of at least 1 week. Gestational age at preterm PROM (odds ratio [OR] 0.75, 95% confidence interval [CI] 0.63-0.90 for each week after 24 weeks of gestation) and cervical dilation at admission (OR 0.66, 95% CI 0.49-0.90 for each centimeter of dilation) were inversely associated with a latency period of at least 1 week. There were no stillbirths (95% CI 0-1%), but the rate of neonatal mortality was 90 per 1,000 newborns (95% CI 57-112) with a 7.3% cerebral palsy rate among survivors (95% CI 4.4-10.3%).

CONCLUSION

In twin pregnancies, preterm PROM from 24 to 31 weeks of gestation is associated with a neonatal mortality rate of 9.0% and an overall cerebral palsy rate of 7.3%. A longer latency period is associated with less advanced cervical dilation and later gestational age at PROM. LEVEL OF EVIEDENCE: II.

Umbilical and fetal middle cerebral artery Doppler reference ranges in a twin population followed longitudinally from 24 to 38 weeks' gestation

OBJECTIVE

To construct monochorionic diamniotic (MCDA) and dichorionic diamniotic (DCDA) twin reference ranges for umbilical artery (UA) pulsatility index (PI), UA resistance index (RI), fetal middle cerebral artery (MCA) PI and peak systolic velocity (PSV) and cerebroplacental ratio (CPR) from 24 weeks' to 38 weeks' gestation and compare these with published normal values for singleton pregnancies.

METHODS

This prospective multicenter cohort study included 1028 unselected twin pairs recruited over a 2-year period. Participants with dichorionic twins underwent fortnightly ultrasound surveillance from 24 weeks' gestation, with monochorionic twins being followed every 2 weeks from 16 weeks until delivery. A total of 7536 fetal Doppler examinations in 618 twin pregnancies were included in the analysis, with reference ranges for MCDA and DCDA pregnancies constructed for each of the Doppler indices using multilevel modeling.

RESULTS

UA-PI and UA-RI appear to be higher in twins than in singletons, and MCA-PI and MCA-PSV appear to be lower. The CPR also appears to be lower in twins than in singletons. Similar MCA indices were observed in MCDA and DCDA twins.

CONCLUSION

We have established longitudinal reference ranges for UA-PI and UA-RI, MCA-PI and MCA-PSV and CPR in twin pregnancies, which appear to differ from those in singleton pregnancies. The derived twin-specific reference ranges may be more appropriate in the surveillance of these high-risk pregnancies. Applying the singleton CPR cut-off of ≤ 1.0 may lead to a large number of false-positive diagnoses of cerebral redistribution in twin fetuses.

Exploring the origins of asthma: Lessons from twin studies

This thesis explores the contribution of twin studies, particularly those studies originating from the Danish Twin Registry, to the understanding of the aetiology of asthma. First, it is explored how twin studies have established the contribution of genetic and environmental factors to the variation in the susceptibility to asthma, and to the variation in several aspects of the clinical expression of the disease such as its age at onset, its symptomatology, its intermediate phenotypes, and its relationship with other atopic diseases. Next, it is explored how twin studies have corroborated theories explaining asthma's recent increase in prevalence, and last, how these fit with the explanations of the epidemiological trends in other common chronic diseases of modernity.

An analysis of pregnancy outcome in dichorionic and monochorionic twins given special antenatal and intranatal care: a four-year survey

OBJECTIVE

The present study aims to analyze perinatal outcomes in twins given special care during pregnancy and labor and to compare fetal and neonatal outcomes in dichorionic twins with monochorionic twins.

STUDY DESIGN

Eighty eight (88) twin pregnancies booked for care at a tertiary care Fetal Medicine centre were included in this study. The maternal demographic variables, course of pregnancy, fetal problems, and specialized fetal therapeutic and diagnostic interventions were noted. The above parameters were compared in the sub-groups of dichorionic and monochorionic twin pregnancies and related to the perinatal outcome. Statistical analysis was done using the student's t test and the two-tailed chi sqaure tests with Yate's continuity correction. A p value <0.05 was considered as significant.

RESULTS

Mean maternal age was 30.34 + 4.81 years (range 19-48). 81 % of the twins were DCDA, and 19 % were MCDA. The mean gestational age at delivery was 34.4 ± 3.5 weeks, and this was not significantly different in MCDA and DCDA groups. Serious fetal problems warranting intervention at the time of initial referral were significantly higher in MCDA twins although overall perinatal outcome in both groups were not different.

CONCLUSION

Specialized care during pregnancy and labor including active fetal surveillance and therapeutic intervention when indicated improves the perinatal outcome in twin pregnancies and ensured at least one healthy live birth in over 90 % cases, although with an increase in late prematurity.

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.

Fetoscopic laser coagulation of the vascular equator versus selective coagulation for twin-to-twin transfusion syndrome: an open-label randomised controlled trial

BACKGROUND

Monochorionic twin pregnancies complicated by twin-to-twin transfusion syndrome are typically treated with fetoscopic laser coagulation. Postoperative complications can occur due to residual vascular anastomoses on the placenta. We aimed to assess the efficacy and safety of a novel surgery technique that uses laser coagulation of the entire vascular equator (Solomon technique).

METHODS

We undertook an open-label, international, multicentre, randomised controlled trial at five European tertiary referral centres. Women with twin-to-twin transfusion syndrome were randomly assigned by online randomisation (1:1) with permuted blocks to the Solomon technique or standard laser coagulation. The primary outcome was a composite of incidence of twin anaemia polycythaemia sequence, recurrence of twin-to-twin transfusion syndrome, perinatal mortality, or severe neonatal morbidity. Analyses were by intention to treat, with results expressed as odds ratios (ORs) and 95% CIs. This trial is registered with the Dutch Trial Registry, number NTR1245.

FINDINGS

Between March 11, 2008, and July 12, 2012, 274 women were randomly assigned to either the Solomon group (n=139) or the standard treatment group (n=135). The primary outcome occurred in 94 (34%) of 274 fetuses in the Solomon group versus 133 (49%) of 270 in the standard treatment group (OR 0·54; 95% CI 0·35-0·82). The Solomon technique was associated with a reduction in twin anaemia polycythaemia sequence (3% vs 16% for the standard treatment; OR 0·16, 95% CI 0·05-0·49) and recurrence of twin-to-twin transfusion syndrome (1% vs 7%; 0·21, 0·04-0·98). Perinatal mortality and severe neonatal morbidity did not differ significantly between the two groups. Outside of the common and well-known complications of twin-to-twin transfusion syndrome and its treatment, no serious adverse events occurred.

INTERPRETATION

Fetoscopic laser coagulation of the entire vascular equator reduces postoperative fetal morbidity in severe twin-to-twin transfusion syndrome. We recommend that fetoscopic surgeons consider adopting this strategy for treatment of women with twin-to-twin transfusion syndrome.

FUNDING

Netherlands Organization for the Health Research and Development (ZonMw 92003545).

Conservative management of fetus papyraceus: a report of two cases

The term fetus papyraceus is used to describe a mummified fetus associated with multiple gestations where one fetus dies and is flattened between the membranes of living fetus and uterine wall. Though the maternal and fetal complications in affected cases can be severe, we report of two cases of fetus papyraceus managed conservatively without any complications. Successful outcome is related to careful monitoring during pregnancy.

Pre-eclampsia (PE) and Chorionicity in Women with Twin Gestations

BACKGROUND

Pre-Eclampsia (PE) affects 6-31% of pregnant women with multiple gestations. There are conflicting reports on the association of PE with Chorionicity and zygosity; however, there is a lack of information on this potential association in a population of pregnant Asian Indian women.

AIM

To determine as to whether chorionicity and zygosity were associated with PE in a population of Asian Indian women with twin gestations.

SETTINGS AND DESIGN

A retrospective observational study was done at a single tertiary care centre in Southern India.

MATERIAL AND METHODS

The study included pregnant women with twin gestations, who was delivered at the study institute in 2012. Hypertension in pregnancy was categorized, based on the criteria of the International Society for the Study of Hypertension in Pregnancy. Chorionicity was determined by using ultrasonography and zygosity was determined, based on clinical criteria. Point estimates and the 95% Confidence Intervals (CI) around point estimates of PE and associations of chorionicity and zygosity with PE were determined by using bivariate analysis, logistic regression models and area under Receiver Operator Characteristic (ROC) curves.

RESULTS

This study included 208 women with twin gestations. The incidence of PE in dichorionic twin gestations was 13.17% (n=22, 95% CI: 8.66, 18.96), it was 4.87% (n=2, 95% CI: 0.83, 15.19) in monochorionic twin gestations, it was 16.36% (n=9, 95% CI: 8.29, 27.91) in dizygous twin gestations and it was 4.88% (n=2, 95% CI: 0.83, 15.19) in monozygous twin gestations. Neither chorionicity (adjusted OR: 2.59, 95% CI: 0.55, 12.19) nor zygosity (adjusted OR 2.72, 95% CI: 0.49, 15.13) were associated with PE In a multivariate logistic regression model.

CONCLUSION

Although it was not statistically significant, the clinical incidence of PE was higher in dichorionic and dizygous twin gestations.

Elective birth at 37 weeks' gestation for women with an uncomplicated twin pregnancy

BACKGROUND

The optimal timing of birth for women with an otherwise uncomplicated twin pregnancy at term is uncertain, with clinical support for both elective delivery at 37 weeks, as well as expectant management (awaiting the spontaneous onset of labour).

OBJECTIVES

To assess a policy of elective delivery from 37 weeks' gestation compared with an expectant approach for women with an otherwise uncomplicated twin pregnancy.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (12 December 2013).

SELECTION CRITERIA

Randomised controlled trials with reported data that compared outcomes in mothers and babies who underwent elective delivery from 37 weeks' gestation in a twin pregnancy with outcomes in controls who were managed expectantly.

DATA COLLECTION AND ANALYSIS

At least two review authors independently assessed trial eligibility, trial quality and extracted data from the included trials.

MAIN RESULTS

Two randomised controlled trials comparing elective birth at 37 weeks for women with an uncomplicated twin pregnancy, with expectant management were included, involving 271 women and 542 infants. One trial was at an overall low risk of bias, and one trial was at unclear risk of selection bias, performance bias and detection bias.There were no statistically significant differences identified between a policy of elective birth at 37 weeks' gestation and expectant management with regards to birth by caesarean section (two studies; 271 participants; risk ratio (RR) 1.05; 95% confidence interval (CI) 0.83 to 1.32); perinatal death or serious perinatal morbidity (two studies; 542 infants; RR 0.34; 95% CI 0.01 to 8.35); or maternal death or serious maternal morbidity (one study; 235 women; RR 0.29; 95% CI 0.06 to 1.38).There were no statistically significant differences identified for the pre-specified secondary maternal and infant review outcomes reported by these two trials between the two treatment policies (including for: haemorrhage requiring blood transfusion; instrumental vaginal birth; meconium-stained liquor; Apgar score less than seven at five minutes; admission to neonatal intensive care; birthweight less than 2500 g; neonatal encephalopathy; and respiratory distress syndrome). While not a pre-specified review outcome, elective birth at 37 weeks, compared with expectant management, was shown to significantly reduce the risk of infants being born with a birthweight less than the third centile (one study; 470 infants; RR 0.30; 95% CI 0.13 to 0.68).

AUTHORS' CONCLUSIONS

Early birth at 37 weeks' gestation compared with ongoing expectant management for women with an uncomplicated twin pregnancy does not appear to be associated with an increased risk of harms, findings which are consistent with the United Kingdom's National Institute for Health and Care Excellence (NICE) recommendations which advocate birth for women with a dichorionic twin pregnancy at 37 + 0 weeks' gestation. It is unlikely that sufficient clinical equipoise exists to allow for the randomisation of women to a later gestational age at birth.

Perinatal asphyxia in monochorionic versus dichorionic twins: incidence, risk factors and outcome

OBJECTIVE

To estimate the incidence, risk factors, severity and outcome after perinatal asphyxia in monochorionic (MC) versus dichorionic (DC) twins.

METHODS

We included all consecutive near-term MC and DC twins with perinatal asphyxia admitted to our neonatal ward between 2004 and 2013 and compared the perinatal characteristics and neonatal outcome between both groups.

RESULTS

The incidence of perinatal asphyxia in MC and DC twin infants was 4.0 (11/272) and 4.0% (8/200; p = 1.00). In contrast to DC twins, asphyxia in MC twins was strongly associated with acute exsanguination and anemia at birth; 64% (7/11) in MC twins and 0% (0/8) in DC twins (p < 0.01). Median hemoglobin level at birth in the MC and DC groups was 11.5 and 18.6 g/dl, respectively (p < 0.01).

CONCLUSIONS

Perinatal asphyxia in MC twins is often associated with severe anemia at birth due to acute hemorrhage through the placental vascular anastomoses.

First-trimester sonographic prediction of obstetric and neonatal outcomes in monochorionic diamniotic twin pregnancies

OBJECTIVES

The purpose of this study was to investigate whether discordant nuchal translucency and crown-rump length measurements in monochorionic diamniotic twins are predictive of adverse obstetric and neonatal outcomes.

METHODS

We conducted a multicenter retrospective cohort study including all monochorionic diamniotic twin pregnancies with two live fetuses at the 11-week to 13-week 6-day sonographic examination who had serial follow-up sonography until delivery. Isolated nuchal translucency, crown-rump length, and combined discordances were correlated with adverse obstetric outcomes, individually and in composite, including the occurrence of 1 or more of the following in either fetus: intrauterine growth restriction (IUGR), twin-twin transfusion syndrome (TTTS), intrauterine fetal death (IUFD), growth discordance (≥ 20%), and preterm birth before 28 weeks' gestation. Correlations with adverse composite neonatal outcomes were also studied. A receiver operating characteristic curve analysis and a logistic regression analysis with a generalized estimating equation were conducted.

RESULTS

Fifty-four of the 177 pregnancies included (31%) had an adverse composite obstetric outcome, with TTTS in 19 (11%), IUGR in 21 (12%), discordant growth in 14 (8%), IUFD in 14 (8%), and preterm birth before 28 weeks in 10 (6%). Of the 254 neonates included in the study, 69 (27%) were complicated by adverse composite neonatal outcomes, with respiratory distress syndrome being the most common (n = 59 [23%]). The areas under the curve for the combined discordances to predict composite obstetric and neonatal outcomes were 0.62 (95% confidence interval, 0.52-0.72), and 0.54 (95% confidence interval, 0.46-0.61), respectively.

CONCLUSIONS

In our population, nuchal translucency, crown-rump length, and combined discordances in monochorionic diamniotic twin pregnancies were not predictive of adverse composite obstetric and neonatal outcomes.

Prospective study of the MD-twin score for antepartum evaluation of monochorionic diamniotic twins and its correlation with perinatal outcomes

AIM

To assess the outcome of monochorionic diamniotic (MD) twins with the aid of the MD-twin score.

METHODS

We enrolled 112 MD-twin women in a tertiary perinatal center from 1997 to 2009. The MD-twin score was prospectively applied once per week to women who did not have twin-to-twin transfusion syndrome (TTTS) after 26 weeks of gestation. The MD-twin score consists of five variables: (i) fetal weight discordance; (ii) amniotic fluid discordance; (iii) hydrops fetalis; (iv) umbilical cord insertion; and (v) fetal heart rate monitoring. Normal was assigned a value of 0, abnormal was assigned 1, and total score was used for evaluation. Women with scores of 2 at 26 weeks gestation were managed expectantly until the score reached 3. Outcome measures were fetal death, neonatal death and neurological sequelae. The incidence of poor outcome according to score was investigated. The characteristics of MD twins with poor outcome were investigated.

RESULTS

MD-twin scores were applied to 90 women. Among them, 79 had scores of 2 or less and all had good outcomes. There were 11 women with a score of 3, four of whom had adverse outcome for at least one twin. Neonates born to women with scores of 0-2 had good outcomes without respect to birthweight percentile, while neonates with scores of 3 had poor outcomes when their birthweight percentile was less than the third percentile.

CONCLUSION

The MD-twin score is applicable to 90% of MD twins without TTTS. An MD-twin score of 2 is reassuring, while a score of 3 indicates increased risks for adverse outcome.

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.

Perinatal complications of monochorionic diamniotic twin gestations with discordant crown-rump length determined at mid-first trimester

AIM

The aim of this study was to investigate the value of discordance of crown-rump length (DCRL) at mid-first trimester to predict adverse outcomes in monochorionic diamniotic twin gestations (MD).

MATERIAL AND METHODS

This was a retrospective cohort study of the perinatal outcome in MD pregnancies managed from the first trimester onward. DCRL was evaluated between 8 and 10 weeks of gestation. The association between DCRL and perinatal complications, including fetal death, twin-twin transfusion syndrome, severe discordant birthweight (DB), and twin anemia-polycythemia sequence, was assessed.

RESULTS

Among 126 cases, a single fetal demise occurred in two (2%) and demise of both fetuses occurred in eight (6%). Five pregnancies (4%) were complicated with twin-twin transfusion syndrome; one case (1%) was twin anemia-polycythemia sequence and 13 (10%) were DB. Neonatal death occurred in one pair. At 28 days of age, in 115 cases (91%) both twins were alive. In 117 cases (93%), at least one twin survived until 28 days of age. DCRL >12.0% was not related to any perinatal complications but DB (P < 0.01; relative risk: 1.40; 95% confidence interval: 1.06-1.84).

CONCLUSIONS

DCRL in MD during the mid-first trimester might be useful for predicting DB.

Does 17-α-hydroxyprogesterone caproate affect fetal biometry and birth weight in twin pregnancy?

OBJECTIVE

Increasingly, maternal administration of 17-α-hydroxyprogesterone caproate (17-OHPC) is utilized to prevent preterm birth, but the fetal safety of 17-OHPC is still a matter of concern. This study aimed to assess whether exposure to 17-OHPC during the second and third trimesters of pregnancy affects fetal biometry in twin gestations.

METHODS

This study included a subset of women with a twin pregnancy who had been previously included in a randomized clinical trial comparing the effectiveness of 17-OHPC and placebo on neonatal outcomes and preterm birth rates in multiple pregnancy. In the present study, the individual growth patterns of femur length, head circumference and abdominal circumference were compared between fetuses of women who had been randomized to receive weekly injections of either 17-OHPC (n = 52) or placebo (n = 58) at between 16-20 and 36 weeks' gestation.

RESULTS

The three biometric variables assessed developed similarly in fetuses in both the group exposed to 17-OHPC and the placebo group during the second half of pregnancy. Birth weight adjusted for parity and fetal sex was also comparable between groups.

CONCLUSION

The use of 17-OHPC has no adverse effects on fetal biometry and birth weight in twins.

[Twin pregnancies: where should we manage them? Where should they deliver?]

OBJECTIVES

To define where should twin pregnancies be managed and delivered.

MATERIALS AND METHODS

A literature search was performed using the Pubmed and Cochrane database. Foreign societies guidelines were also consulted.

RESULTS

There is little or no evidence to answer the question. Risk of premature labor and chorionicity are the two main factors involved in twin management. When there is a risk of prematurity, in utero transfer is recommended. Twin care must be performed by a team trained in the specificity of management according to chorionicity. There is not enough evidence to support specialized clinics. Labor and delivery need permanent and immediate disponibility of a perinatal team including an OB-gyn, an anesthesiologist and a pediatrician.

CONCLUSION

Needs assessment and chorionicity are the best indicators to define the optimal place of care and delivery for twin pregnancies. More than a specific location, it seems more logical to define all necessary means to enforce an optimal management of these pregnancies.

Cause-specific mortality of very preterm infants and antenatal events

OBJECTIVE

To assess the relationship between antenatal factors and cause-specific risk of death in a large area-based cohort of very preterm infants.

STUDY DESIGN

The ACTION (Accesso alle Cure e Terapie Intensive Ostetriche e Neonatali) study recruited during an 18-month period all infants 22-31 weeks' gestational age admitted to neonatal care in 6 Italian regions (n=3040). We analyzed the data of 2974 babies without lethal or acutely life-threatening malformations. Cause-specific risks of death adjusted for competing causes were calculated, and region-stratified multiple Cox regression analyses were used to study the association between cause-specific mortality and infants' characteristics, pregnancy complications, antenatal steroids, and place of birth.

RESULTS

Deaths attributable to respiratory problems and intraventricular hemorrhage prevailed in the first 2 weeks of life, and those attributable to infections and gastrointestinal diseases afterwards. Antepartum hemorrhage was associated with respiratory deaths (hazard ratio [HR] 1.6, 95% CI 1.1-2.4), and maternal infection with deaths attributable to asphyxia (HR 32.5, 95% CI 4.1-259.4) and to respiratory problems (HR 2.8, 95% CI 1.6-5.2). Preterm premature rupture of membranes increased the likelihood of deaths due to neonatal infection (HR 1.8, 95% CI 1.0-3.1), and preterm labor/contractions of those due to respiratory (HR 1.5, 95% CI 1.1-2.0) and gastrointestinal diseases (HR 5.8, 95% CI 2.1-16.3). In addition, a birth weight z-score<-1 was associated with increasing hazards of death resulting from asphyxia, late infections, respiratory, and gastrointestinal diseases.

CONCLUSIONS

Different complications of pregnancy lead to different cause-specific mortality patterns in very preterm infants.

Discordance in neonatal risk factors and early childhood outcomes of very low birth weight (<1.5 kg) twins

OBJECTIVE

To examine the rates of discordance in neonatal risk factors and neurodevelopmental outcomes within very low birth weight twin pairs and the factors associated with discordant outcomes.

STUDY DESIGN

Rates of neonatal risk factors and neurodevelopmental outcomes, and discordance in outcomes were examined for 88 very low birth weight twin pairs born between 1990 and 2005 and followed through 20 months' corrected age.

RESULT

Discordance rates ranged from 17 to 42% for neonatal risk factors and from 18 to 31% for neurodevelopmental outcomes. In regression analysis, affected co-twins were significantly more likely to have had an abnormal cerebral ultrasound than their unaffected co-twins in pairs discordant for cerebral palsy (odds ratio (OR): 13.00, 95% confidence interval (CI): 2.22 to 76.03)) and in pairs discordant for neurodevelopmental impairment (OR: 4.00, 95% CI: 1.13 to 14.18). Outcomes and discordance in outcomes were similar for monochorionic and dichorionic pairs.

CONCLUSION

Despite shared genetics and risk factors, twins may have discordant outcomes. Information on discordant neonatal and neurodevelopmental outcomes is important for counseling families of twins.

[Perinatal outcome of monochorionic and dichorionic twin gestations: a study of 775 pregnancies at Reunion Island]

OBJECTIVES

To compare the perinatal mortality and morbidity of infants born from monochorionic versus dichorionic twin pregnancies (TP).

PATIENTS AND METHODS

Retrospective, comparative study of monochorionic and dichorionic TP over 10 years in the south of Reunion Island. Information regarding demographic, gestational and perinatal variables of mothers and infants was collected from the hospital perinatal database.

RESULTS

Six hundred and twenty dichorionic and 155 monochorionic TP were analyzed. In case of monochorionic TP, mothers had higher rates of pregnancy-related hypertension (OR=1.82, 95%CI=[1.02-3.29] ; P=0.03) and hospitalization (OR=1.48, 95%CI=[1.02-2.16]; P=0.03). Newborns from monochorionic TP had higher morbidity for : very preterm birth (birth before 33 weeks gestation) (OR=1.65, 95%CI=[1.02-2.66]; P=0.02), very low birth weight (birth weight<1500g) (OR=1.73, 95%CI=[1.57-3.13]; P<0.001), Apgar<7 at 1 minute (OR=1.76, 95%CI=[1.18-2.61]; P<0.01) and hospitalization (OR=2.08, 95%CI=[1.58-2.73]; P<0.001). Perinatal mortality was also significantly higher (OR=2.47, 95%CI=[1.54-3.94]; P<0.001), as well intrauterine fetal death (OR=3.96, 95%CI=[1.95-8.05]; P<0.001) CONCLUSION: This study confirms that few differences exist among dichorionic and monochorionic TP with regard to maternal morbidity, while neonatal morbidity and mortality are higher in twins born from monochorionic pregnancies.

Does risk of preeclampsia differ by twin chorionicity?

OBJECTIVE

Examine whether dichorionic (DC) and monochorionic (MC) twins exhibit different rates and severity of preeclampsia.

METHODS

Retrospective cohort study of 695 twin pregnancies from 2002 to 2007. DC pregnancies were compared to MC pregnancies, with the primary outcome of interest being development of preeclampsia, and the secondary outcome being severity of preeclampsia. Chi square test compared proportions and multivariable analyses controlled for potential confounders.

RESULTS

Any preeclampsia developed in 21.1% (104/492) of DC and 10.8% (22/203) of MC pregnancies (p = 0.001), mild preeclampsia in 13.8% (68/492) of DC and 4.9% (10/203) of MC pregnancies (p = 0.001) and severe preeclampsia in 7.3% (36/492) of DC and 5.9% (12/203) of MC pregnancies (p = 0.506). DC pregnancies showed higher odds of mild preeclampsia compared to MC pregnancies (aOR 5.85, 95% CI 1.31-26.13) after controlling for several potential confounders including gestational age at delivery.

CONCLUSIONS

A statistically significant larger proportion of women with DC twins developed any preeclampsia, and specifically mild preeclampsia, compared to those with MC twins. Additionally, after controlling for several potential confounders, women with DC pregnancies demonstrated higher odds of developing mild preeclampsia compared to those with MC pregnancies. Mechanisms of preeclampsia development may differ by twin chorionicity.

B-type natriuretic peptide levels are correlated with birth-weight discordance in monochorionic-diamniotic twins without twin-twin transfusion syndrome

OBJECTIVE

To determine whether B-type natriuretic peptide (BNP) levels in umbilical cord blood (UCB) and amniotic fluid (AF) are correlated with birth-weight discordances in monochorionic-diamniotic twins.

STUDY DESIGN

The UCB-BNP and AF-BNP levels were determined at birth in 36 twin-pairs without twin-twin transfusion syndrome (TTTS).

RESULT

Both the UCB-BNP and the AF-BNP levels were significantly higher among twins with either a birth-weight discordance ≥20% (141.6 versus 52.9 pg ml(-1) for UCB-BNP, 38.0 versus 17.2 pg ml(-1) for AF-BNP) or cardiac dysfunction at birth (167.2 versus 56.3 pg ml(-1) for UCB-BNP, 34.9 versus 19.0 pg ml(-1) for AF-BNP), compared with neonates without the respective characteristics. The UCB-BNP and AF-BNP levels in both the larger and the smaller twins were significantly correlated with birth-weight discordance.

CONCLUSION

Cardiac dysfunction occurs in both larger and smaller co-twins with increasing birth-weight discordances, even in the absence of TTTS.

Active management of selective intrauterine growth restriction with abnormal Doppler in monochorionic diamniotic twin pregnancies diagnosed in the second trimester of pregnancy

OBJECTIVE

This study aims to compare outcomes of active management of monochorionic diamniotic twin pregnancies complicated with severe intrauterine growth restriction (IUGR) of one twin before 24 weeks with continuous or intermittent absent or reversed end-diastolic flow (AREDF) in the umbilical artery, with or without twin-to-twin transfusion syndrome (TTTS).

METHOD

This study is a retrospective comparison of 45 consecutive cases of severe selective IUGR (s-IUGR) defined as an estimated fetal weight at or below the fifth centile with a >25% weight discordance and AREDF in the umbilical artery before 24 weeks and 166 consecutive cases of TTTS stage III, with AREDF in the donor (TTTS3D) and also with s-IUGR. These were treated by either selective laser photocoagulation of chorionic vessels (SLPCV) or cord coagulation (CC).

RESULTS

The 166 cases of TTTS3D were treated by SLPCV, whereas 23 and 22 cases of s-IUGR were treated by SLPCV and CC, respectively. Overall survival was 52.17% or 45.45% in s-IUGR treated by SLPCV or CC, respectively, and 48.49% in TTTS3D. The survival of appropriately grown for gestational age (AGA) twins following CC (90.9%) was higher than that following SLPCV in s-IUGR (74%) or in recipient twins of TTTS3D (55.42%) (p = 0.001). Survival of the IUGR twin was 30% and 41.56% with SLPCV in s-IUGR and TTTS3D, respectively.

CONCLUSIONS

Active management of severe IUGR with AREDF in the umbilical artery seems beneficial. Survival rates with SLPCV were similar in s-IUGR and TTTS3D. However, there was a trend for higher survival rates in the AGA twin for CC. The choice of the technique should be driven by objective counseling on survival of both IUGR and AGA twins and therefore by the utility-based ethical values expressed by the pregnant woman.

Neonatal respiratory morbidity in twins versus singletons after elective prelabor caesarean section

OBJECTIVE

To compare the rate of neonatal respiratory morbidity in singletons versus twins delivered by pre-labour caesarean section.

STUDY DESIGN

Uncomplicated pregnancies delivered by prelabor caesarean section at 34+0 to 37+6 weeks' gestation were retrospectively selected. For both singletons and twins caesarean delivery was undertaken electively only after amniocentesis and if the lecithin/sphingomyelin ratio was ≥2. Neonatal respiratory morbidity was compared in twins versus singletons.

RESULTS

241 singletons and 100 twin neonates were included. Overall neonatal respiratory morbidity was comparable between the two groups (25/241 (11.7%) versus 7/100 (7%), p=.331). Between 34+0 and 36+6 weeks, however, the risk was higher among singleton than twins (15/46 (32.6%) versus 6/72 (8.3%), p<.001). At multiple regression, dichorionicity, gestational age at delivery ≥37 weeks and female sex independently decreased the risk of neonatal respiratory morbidity.

CONCLUSION

The risk of neonatal respiratory morbidity after elective caesarean section seems lower among twins, especially prior to 37+0 weeks.

Adult glucose metabolism in extremely birthweight-discordant monozygotic twins

AIMS/HYPOTHESIS

Low birthweight (BW) is associated with increased risk of type 2 diabetes. We compared glucose metabolism in adult BW-discordant monozygotic (MZ) twins, thereby controlling for genetic factors and rearing environment.

METHODS

Among 77,885 twins in the Danish Twin Registry, 155 of the most BW-discordant MZ twin pairs (median BW difference 0.5 kg) were assessed using a 2 h oral glucose tolerance test with sampling of plasma (p-)glucose, insulin, C-peptide, glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1. HOMA for beta cell function (HOMA-β) and insulin resistance (HOMA-IR), and also insulin sensitivity index (BIGTT-SI) and acute insulin response (BIGTT-AIR), were calculated. Subgroup analyses were performed in those with: (1) double verification of BW difference; (2) difference in BW >0.5 kg; and (3) no overt metabolic disease (type 2 diabetes, hyperlipidaemia or thyroid disease).

RESULTS

No intra-pair differences in p-glucose, insulin, C-peptide, incretin hormones, HOMA-β, HOMA-IR or BIGTT-SI were identified. p-Glucose at 120 min was higher in the twins with the highest BW without metabolic disease, and BIGTT-AIR was higher in those with the highest BW although not in pairs with a BW difference of >0.5 kg.

CONCLUSIONS/INTERPRETATION

BW-discordant MZ twins provide no evidence for a detrimental effect of low BW on glucose metabolism in adulthood once genetic factors and rearing environment are controlled for.

The Peri/Postnatal Epigenetic Twins Study (PETS)

The Peri/postnatal Epigenetic Twins Study (PETS) is a longitudinal cohort of 250 pairs of Australian twins and their mothers, who were recruited mid-way through pregnancy from January 2007 to September 2009. The study is centered on the developmental origins of health and disease paradigm (DOHaD) in which an adverse intrauterine environment predisposes the individual to complex disease in later life by reducing growth in utero and adversely altering developmental plasticity. Data concerning diet and lifestyle were collected from mothers during pregnancy, and samples of plasma and serum taken at 28 weeks’ gestation. We attended 75% of all births, at which time we collected multiple biological samples including placenta, cord blood, and neonatal cheek cells, the latter from 91% of pairs. Chorionicity was recorded and zygosity was determined by DNA testing where necessary. Approximately 40% of the twins are monozygotic, two-thirds of which are dichorionic. Twins were seen again at 18 months of age and repeat blood and cheek swabs taken where possible. Studies of gene expression and the epigenetic marks of DNA methylation have so far revealed that twins exhibit a wide range of epigenetic discordance at birth, that one-third of the epigenome changes significantly between birth and 18 months; shared (maternal) environment, genetic factors, and non-shared intrauterine environment contribute to an increasing proportion of epigenetic variation at birth, respectively, and affect tissues differently, and that within-pair birth weight discordance correlates with epigenetic discordance in genes associated with lipid metabolism, supporting an epigenetic mechanism for DOHaD.

Behavior genetics and postgenomics

The science of genetics is undergoing a paradigm shift. Recent discoveries, including the activity of retrotransposons, the extent of copy number variations, somatic and chromosomal mosaicism, and the nature of the epigenome as a regulator of DNA expressivity, are challenging a series of dogmas concerning the nature of the genome and the relationship between genotype and phenotype. According to three widely held dogmas, DNA is the unchanging template of heredity, is identical in all the cells and tissues of the body, and is the sole agent of inheritance. Rather than being an unchanging template, DNA appears subject to a good deal of environmentally induced change. Instead of identical DNA in all the cells of the body, somatic mosaicism appears to be the normal human condition. And DNA can no longer be considered the sole agent of inheritance. We now know that the epigenome, which regulates gene expressivity, can be inherited via the germline. These developments are particularly significant for behavior genetics for at least three reasons: First, epigenetic regulation, DNA variability, and somatic mosaicism appear to be particularly prevalent in the human brain and probably are involved in much of human behavior; second, they have important implications for the validity of heritability and gene association studies, the methodologies that largely define the discipline of behavior genetics; and third, they appear to play a critical role in development during the perinatal period and, in particular, in enabling phenotypic plasticity in offspring. I examine one of the central claims to emerge from the use of heritability studies in the behavioral sciences, the principle of minimal shared maternal effects, in light of the growing awareness that the maternal perinatal environment is a critical venue for the exercise of adaptive phenotypic plasticity. This consideration has important implications for both developmental and evolutionary biology.

Pregnancy loss after chorionic villus sampling and genetic amniocentesis in twin pregnancies: a systematic review

OBJECTIVE

To review the available evidence regarding pregnancy loss following first-trimester chorionic villus sampling (CVS) and mid-trimester genetic amniocentesis in twins.

METHODS

We searched the MEDLINE database from January 1990 to May 2011 for randomized and cohort studies reporting on the risk of pregnancy loss after first-trimester CVS performed between 9 and 14 weeks and after genetic amniocentesis performed between 14 and 22 weeks. Where appropriate, we calculated pooled proportions and relative risks with 95% CI.

RESULTS

No randomized studies were found. For CVS, nine studies fulfilled the inclusion criteria. The overall pregnancy-loss rate was 3.84% (95% CI, 2.48-5.47; n = 4). The rate of pregnancy loss before 20 weeks was 2.75% (95% CI, 1.28-4.75; n = 3) and before 28 weeks was 3.44% (95% CI, 1.67-5.81; n = 3). For amniocentesis, the overall pregnancy-loss rate was 3.07% (95% CI, 1.83-4.61; n = 4). The rate of pregnancy loss before 20 weeks was 2.25% (95% CI, 1.23-3.57; n = 2), before 24 weeks was 2.54% (95% CI, 1.43-3.96; n = 9) and before 28 weeks was 1.70% (95% CI, 0.37-3.97; n = 5). Pooled data from four case-control studies showed a higher risk (2.59% vs. 1.53%) of pregnancy loss before 24 weeks following amniocentesis (relative risk = 1.81; 95% CI, 1.02-3.19). There were no statistically significant differences in reported pregnancy loss between transabdominal and transcervical approaches, use of a single-needle system vs. a double-needle system and single uterine entry vs. double uterine entry in the CVS group. Similarly, in the amniocentesis group, there was no statistically significant difference in fetal loss between the single uterine entry vs. the double uterine entry.

CONCLUSION

In the absence of randomized studies, it is not possible to estimate accurately the excess risk following invasive procedures in twins. Currently available data show similar overall pregnancy-loss rates for both amniocentesis and CVS with the excess risk of around 1% above the background risk.

Twin births: cesarean section or vaginal delivery?

OBJECTIVE

To assess morbidity and mortality in twin pregnancy deliveries, according to chorionicity and mode of delivery.

DESIGN

Population-based retrospective cohort.

SETTING

Fourteen obstetric departments in Denmark.

POPULATION

One thousand one hundred and seventy-five twin pregnancies with two live fetuses at 36(+0) weeks of gestation.

METHODS

Pregnancy outcomes assessed according to chorionicity and mode of delivery.

MAIN OUTCOME MEASURES

Poor outcome defined as five min Apgar score ≤ 7, umbilical artery pH < 7.10, admission to neonatal unit for more than three days or death.

RESULTS

Dichorionic (DC) twins, delivered after 36 gestational weeks, with intended vaginal delivery (n= 689) compared with DC twins with planned cesarean section (n= 371) had an increased risk of poor outcome [odds ratio (OR) 1.47, p= 0.037] after adjustment for body mass index, parity and weight discordance. There was no increased risk for poor outcome in monochorionic (MC) twins with intended vaginal delivery (n= 63) compared with planned cesarean section (n= 52; OR 0.87, 95% confidence interval 0.26-2.96). Nulliparity increased the risk of poor outcome in DC (OR 1.5, p= 0.03) and in MC twins (OR 4.01, p= 0.02), as well as birthweight discordance >300 g (DC, OR 1.50, p= 0.02; and MC, OR 6.02, p= 0.002). For DC twins, we found a significantly higher risk of poor outcome of the second-born twin compared with the first (OR 1.64, p= 0.001).

CONCLUSIONS

Dichorionic twins born after 36 weeks of gestation had a higher risk of poor outcome by intended vaginal delivery than by planned cesarean section. For MC twins, statistical differences in outcome by mode of delivery could not be seen.

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

OBJECTIVE

To evaluate whether for women with an uncomplicated twin pregnancy, elective birth at 37 weeks of gestation was associated with reduced risk of death or serious outcomes for babies, without increasing harm.

DESIGN

Randomised controlled trial.

SETTING

Maternity hospitals across Australia, New Zealand and Italy.

POPULATION

A total of 235 women with an uncomplicated twin pregnancy at 36(+6) weeks of gestation, with no contraindication to continuing their pregnancy.

METHODS

Using a computer-generated, central telephone randomisation service, 235 women were randomised to Elective Birth (birth at 37 weeks; n=116) or Standard Care (continued expectant management, with birth planned from 38 weeks; n=119). Outcome assessors were masked to treatment allocation.

MAIN OUTCOME MEASURE

A composite of serious adverse outcome for the infant.

RESULTS

For women with an uncomplicated twin pregnancy, elective birth at 37 weeks of gestation was associated with a significant reduction in risk of serious adverse outcome for the infant (Elective Birth 11/232 [4.7%] versus Standard Care 29/238 [12.2%]; risk ratio [RR] 0.39; 95% CI 0.20-0.75; P=0.005), reflecting a reduction in birthweight less than the third centile using singleton gestational age-specific charts (Elective Birth 7/232 [3.0%] versus Standard Care 24/238 [10.1%]; RR 0.30; 95% CI 0.13-0.67; P=0.004). In a post hoc analysis using twin gestational age-specific charts, there was evidence of a trend towards a reduction in the primary composite of serious adverse infant outcome (Elective Birth Group 4/232 [1.7%] versus Standard Care Group 12/238 [5.0%]; RR 0.34; 95% CI 0.11 to 1.05; P=0.06).

CONCLUSION

The findings of our study support recommendations for women with an uncomplicated twin pregnancy to birth at 37 weeks of gestation.

Optimum timing for planned delivery of uncomplicated monochorionic and dichorionic twin pregnancies

OBJECTIVE

To determine the optimum timing for planned delivery of uncomplicated monochorionic and dichorionic twin pregnancies.

METHODS

Unselected twin pregnancies were recruited for this prospective cohort study (N=1,028), which was conducted in eight tertiary referral perinatal centers in Ireland. Perinatal mortality and a composite measure of perinatal morbidity (respiratory distress, necrotizing enterocolitis, hypoxic ischemic encephalopathy, periventricular leukomalacia, or sepsis) were compared between uncomplicated twins that underwent planned preterm delivery compared with monochorionic twins that continued in utero beyond 34 weeks of gestation, and dichorionic twins who continued beyond 36 weeks.

RESULTS

Perinatal outcome data were recorded for 100% of the 1,001 twin pairs that completed the study (n=200 monochorionic and n=801 dichorionic). Overall perinatal mortality was 30 per 1,000 in monochorionic twins and 3.8 per 1,000 among dichorionic twins. The prospective risk of in utero death was 1.5% after 34 weeks of gestation for uncomplicated monochorionic pregnancies, with no deaths among dichorionic twins after 33 weeks. The risk of a composite measure of perinatal morbidity for uncomplicated monochorionic twins fell from 41% (13/32 neonates, 3/6 among elective deliveries) at 34 weeks to 5% (4/84) at 37 weeks (P<.001). Among dichorionic twins, the risk of morbidity fell from 4% (2/52) among elective deliveries at 36 weeks to 1% (5/344) in pregnancies continuing to 38 weeks (P=.231).

CONCLUSION

Applying a strategy of close fetal surveillance, perinatal morbidity can be minimized by allowing uncomplicated monochorionic pregnancies continue to 37 weeks of gestation and dichorionic twins to 38 weeks. Among monochorionic twins, this approach must be balanced against a 1.5% risk of late in utero death.

Prospective risk of late stillbirth in monochorionic twins: a regional cohort study

OBJECTIVE

Monochorionic (MC) pregnancies are routinely delivered electively at late preterm gestation with the aim of avoiding stillbirth at term. The aim of this study was to evaluate the prospective risk of late stillbirth in a large regional cohort of twin pregnancies of known chorionicity.

METHODS

This was a retrospective study of all twin pregnancy births of known chorionicity between 2000 and 2009 from a large regional cohort consisting of nine hospitals. Prospective risk was calculated per 1000 fetuses rather than pregnancies, as each twin pregnancy had two gestations at risk of stillbirth.

RESULTS

A total of 3005 twin pregnancies delivered after 26 weeks' gestation in the Southwest Thames Obstetric Research Collaborative. The total risk of stillbirth after 26 weeks in MC twins (19.1 per 1000 fetuses) was significantly higher than in dichorionic (DC) twins (6.5 per 1000 fetuses), with an odds ratio (OR) of 2.97 (95% CI, 1.71-5.18). The risk of stillbirth in MC twins did not change significantly between 26 weeks (1.8 per 1000 fetuses) and 36 weeks (3.4 per 1000 fetuses), with an OR of 1.85 (95% CI, 0.3-13.2). The equivalent figures for DC twins were 0.6 per 1000 fetuses and 2.1 per 1000 fetuses, respectively (OR, 3.4 (95% CI, 0.9-13.2)).

CONCLUSIONS

The risk of stillbirth in MC twins does not appear to increase significantly near term. This may be due to a policy of routine surveillance and elective delivery from 36 weeks. The data do not support a policy of elective delivery before 36 weeks' gestation in MC pregnancies.