Fetal or infant death in twin pregnancy: neurodevelopmental consequence for the survivor

Outcome of Twin Pregnancies Complicated by a Single Intrauterine Death

Objective

Single intrauterine fetal death (sIUFD) occurs in approximately 6% of twin pregnancies. If it occurs in the second and third trimesters, it places the co-twin at substantial risk, including that of preterm delivery and associated comorbidities of prematurity or neonatal death. The aim of this present study was to determine the outcome of surviving co-twins following spontaneous single intrauterine fetal death.

Methods

This is a retrospective, observational, cohort study that included all twin pregnancies delivered between January 2015 to December 2019 with a gestational age of 24 weeks or more. Maternal data included were: age, medical illnesses, conceivable methods, chorionicity, and complications during pregnancy. Gestational age of intrauterine fetal demise, gestational age of the surviving twin delivery, mode of delivery, and medications used during pregnancy were also recorded. Neonatal data included: gestational age, gender, birth weight, Apgar score, and complications of prematurity.

Results

Twenty-two pregnancies were found to be complicated by sIUFD and included in the present study (group 1), compared to 26 twins with no sIUFD (group 2). The incidence of sIUFD in twin pregnancies after 20 weeks of pregnancy was 4.4%. The gestational age (weeks) in group 1 was 34.5 (29-39) and in group 2 was 32 (26-38). The frequency of preterm delivery 81.8% in group 1 (59% monochorionic) and 69.2% (100% dichorionic) in group 2. No significant statistical differences were found between the two groups in complications of prematurity.

Conclusions

We conclude that delaying delivery in twin pregnancies complicated by single intrauterine demise with regular follow-up may lead to delivering infants with fewer complications of prematurity.

Risks of nonchromosomal birth defects, small-for-gestational age birthweight, and prematurity with in vitro fertilization: effect of number of embryos transferred and plurality at conception versus at birth

PURPOSE

Excess embryos transferred (ET) (> plurality at birth) and fetal heartbeats (FHB) at 6 weeks' gestation are associated with reductions in birthweight and gestation, but prior studies have been limited by small sample sizes and limited IVF data. This analysis evaluated associations between excess ET, excess FHB, and adverse perinatal outcomes, including the risk of nonchromosomal birth defects.

METHODS

Live births conceived via IVF from Massachusetts, New York, North Carolina, and Texas included 138,435 children born 2004-2013 (Texas), 2004-2016 (Massachusetts and North Carolina), and 2004-2017 (New York) were classified by ET and FHB. Major birth defects were reported by statewide registries within the first year of life. Logistic regression was used to estimate adjusted odds ratios (AORs) and 95% CIs of the risks of a major nonchromosomal birth defect, small-for-gestational age birthweight (SGA), low birthweight (LBW), and preterm birth (≤36 weeks), by excess ET, and excess ET + excess FHB, by plurality at birth (singletons and twins).

RESULTS

In singletons with [2 ET, FHB =1] and [≥3 ET, FHB=1], risks [AOR (95% CI)] were increased, respectively, for major nonchromosomal birth defects [1.13 (1.00-1.27) and 1.18 (1.00-1.38)], SGA [1.10 (1.03-1.17) and 1.15 (1.05-1.26)], LBW [1.09 (1.02-1.13) and 1.17 (1.07-1.27)], and preterm birth [1.06 (1.00-1.12) and 1.14 (1.06-1.23)]. With excess ET + excess FHB, risks of all adverse outcomes except major nonchromosomal birth defects increased further for both singletons and twins.

CONCLUSION

Excess embryos transferred are associated with increased risks for nonchromosomal birth defects, reduced birthweight, and prematurity in IVF-conceived births.

Fetal stroke and cerebrovascular disease: Advances in understanding from lenticulostriate and venous imaging, alloimmune thrombocytopaenia and monochorionic twins

Fetal stroke is an important cause of cerebral palsy but is difficult to diagnose unless imaging is undertaken in pregnancies at risk because of known maternal or fetal disorders. Fetal ultrasound or magnetic resonance imaging may show haemorrhage or ischaemic lesions including multicystic encephalomalacia and focal porencephaly. Serial imaging has shown the development of malformations including schizencephaly and polymicrogyra after ischaemic and haemorrhagic stroke. Recognised causes of haemorrhagic fetal stroke include alloimmune and autoimmune thrombocytopaenia, maternal and fetal clotting disorders and trauma but these are relatively rare. It is likely that a significant proportion of periventricular and intraventricular haemorrhages are of venous origin. Recent evidence highlights the importance of arterial endothelial dysfunction, rather than thrombocytopaenia, in the intraparenchymal haemorrhage of alloimmune thrombocytopaenia. In the context of placental anastomoses, monochorionic diamniotic twins are at risk of twin twin transfusion syndrome (TTTS), or partial forms including Twin Oligohydramnios Polyhydramnios Sequence (TOPS), differences in estimated weight (selective Intrauterine growth Retardation; sIUGR), or in fetal haemoglobin (Twin Anaemia Polycythaemia Sequence; TAPS). There is a very wide range of ischaemic and haemorrhagic injury in a focal as well as a global distribution. Acute twin twin transfusion may account for intraventricular haemorrhage in recipients and periventricular leukomalacia in donors but there are additional risk factors for focal embolism and cerebrovascular disease. The recipient has circulatory overload, with effects on systemic and pulmonary circulations which probably lead to systemic and pulmonary hypertension and even right ventricular outflow tract obstruction as well as the polycythaemia which is a risk factor for thrombosis and vasculopathy. The donor is hypovolaemic and has a reticulocytosis in response to the anaemia while maternal hypertension and diabetes may influence stroke risk. Understanding of the mechanisms, including the role of vasculopathy, in well studied conditions such as alloimmune thrombocytopaenia and monochorionic diamniotic twinning may lead to reduction of the burden of antenatally sustained cerebral palsy.

The Effect of Twin Birth on Neonatal and Infant Mortality Rates: A Systematic Review

Background and aims: Twin birth may account for higher mortality rates in infants and neonates. To investigate the potential relationship between twin birth and infant and neonatal mortality rates (NMRs), a systematic review was conducted. Methods: To gather the evidence for the relationship between twin birth and its potential effect on mortality during infancy and neonatal periods, a systematic review was conducted. The most important used databases were PubMed, Google Scholar, Web of Science, Scopus, ProQuest, Cochrane and Springer. Then, the databases were searched by appropriate keywords. After reviewing and evaluating the collected studies, trends in the different countries were compared. Results: A total of 13 790 related studies were found, of which 128 studies were selected in the first step. The studies which were not related to the subject, in addition to repetitive studies, were excluded from the search in the second step based on inclusion and exclusion criteria by reviewing the abstract and, in some cases, the full article. Finally, 7 studies entered the last step. Conclusion: This study showed that the mortality could be higher among twins than among non-twins, especially among boys.

Birth Outcomes by Infertility Treatment: Analyses of the Population-Based Cohort: Massachusetts Outcomes Study of Assisted Reproductive Technologies (MOSART)

OBJECTIVE

To evaluate pregnancy and birth outcomes by type of infertility treatment received.

STUDY DESIGN

Assisted reproductive technology (ART) data on women who were both treated and gave birth in Massachusetts were linked to vital records and hospital data. Singleton and twin live births were categorized by ART treatment parameters. Risks for adverse outcomes (pregnancy-induced hypertension [PIH], gestational diabetes [GDM, primary cesarean [CS], prematurity [PTB], low birthweight [LBW], small for gestational age [SGA], large for gestational age [LGA], and birth defects [BD]) were modeled using logistic regression (adjusted odds ratios and 95% confidence intervals), adjusted for parental and treatment factors. GDM and PIH were additionally modeled as adverse outcomes.

RESULTS

Among the 8,948 pregnancies, risks were significantly higher among twins (PIH 2.58, GDM 1.30, CS 5.83, PTB 11.84, LBW 10.68, SGA 2.17, BD 2.54), donor oocytes (PIH 1.87, CS 1.43, PTB 1.43), ICSI (SGA 1.20), and the presence of > 1 fetal heartbeat at 6 weeks' gestation (2 fetal heartbeats: PTB 1.49, LBW 1.57; 3 fetal heartbeats: PTB 2.07, LBW 2.30, SGA 2.04). Thawed embryos were associated with a higher risk for PIH (1.30) but lower risks for LBW (0.79) and SGA (0.38). GDM was associated with increased risks for CS (1.22), LGA (1.40), and BD (1.50); PIH was associated with risks for CS (1.86), PTB (2.70), and LBW (1.83).

CONCLUSION

Plurality is the predominant ART treatment risk factor associated with substantial excess morbidity for both mother and infants.

Adverse pregnancy outcomes after in vitro fertilization: effect of number of embryos transferred and plurality at conception

OBJECTIVE

To evaluate risks for adverse pregnancy outcomes by number of embryos transferred (ET) and fetal heartbeats (FHB) in assisted reproductive technology-conceived singleton live births.

DESIGN

Longitudinal cohort using cycles reported to the Society for Assisted Reproductive Technology Clinic Outcomes Reporting System between 2004 and 2008 among women who were treated and gave birth in Massachusetts.

SETTING

Not applicable.

PATIENT(S)

Assisted reproductive technology data on 6,073 births between 2004 and 2008 were linked to vital records and hospital data. Likelihood of ET ≥3 vs. 1-2, FHB >1 vs. 1, and risks of preterm birth (PTB, <37 weeks' gestation), low birth weight (LBW, <2,500 g), and small-for-gestational-age birth weight (SGA, <10th percentile) with FHB >1 were modeled with binary logistic regression using a backward-stepping algorithm, and presented as adjusted odds ratios (95% confidence intervals).

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

ET ≥3, FHB >1, PTB, LBW, and SGA.

RESULT(S)

Higher ET was significantly more likely with older maternal age, intracytoplasmic sperm injection, assisted hatching, cleavage-stage embryos, and thawed embryos. The likelihood of FHB >1 with ≥3 ET vs. 1-2 ET was 2.04 (1.68-2.48). Risks of PTB and LBW with FHB >1 were 1.63 (1.27-2.09) and 1.81 (1.36-2.39), respectively; the risk of SGA was not significant. Nulliparity was associated with higher risks of PTB (1.34 [1.12-1.59]), LBW (1.48 [1.20-1.83]), and SGA (2.17 [1.69-2.78]).

CONCLUSION(S)

Number of embryos transferred was strongly associated with FHBs, with twice the risk of FHB >1 with ≥3 ET vs. 1-2 ET. Increasing FHBs were associated with significantly greater risks for PTB and LBW outcomes.

Do very preterm twins and singletons differ in their neurodevelopment at 5 years of age?

OBJECTIVE

Twins have inconsistently shown poorer outcomes than singletons. Although a high proportion of twins are born very preterm, data are sparse on the long-term outcomes in very preterm twins. The objective of this study was to compare mortality and neurodevelopmental outcomes of very preterm singletons and twins and to study outcomes in relation to factors specific to twins.

DESIGN

Birth cohort study Etude Epidemiologique sur les Petits Ages Gestationnels (EPIPAGE).

SETTING

Nine regions in France.

PATIENTS

All very preterm live births occurring from 22 to 32 weeks of gestation in all maternity wards of nine French regions in 1997 (n=2773).

MAIN OUTCOMES MEASURES

Neurodevelopmental status, including cerebral palsy, and a cognitive assessment with the Kaufman Assessment Battery for Children, with scores on the Mental Processing Composite (MPC) scale, was available for 1732 and 1473 children at 5 years of age, respectively.

RESULTS

Among live births, twins had higher hospital mortality than singletons (adjusted (a)OR: 1.4 (95% CI 1.1 to 1.9)). Among survivors, there was no crude difference at 5 years between twins and singletons in the prevalence of cerebral palsy (8.0% vs 9.1%, respectively), MPC <70 (9.5% vs 11.1%) and mean MPC (94.6 vs 94.4). However, after adjustment for sex, gestational age, intrauterine growth restriction and social factors, twins were more likely to have lower MPC scores (mean difference: -2.4 (95% CI-4.8 to 0.01)). Live born twins had a higher risk of mortality when birth weight discordance was present (aOR:2.9 (95% CI 1.7 to 4.8)), but there were no differences in long-term outcomes.

CONCLUSIONS

Compared with very preterm singletons, twins had higher mortality, no difference with respect to severe deficiencies, but slightly lower MPC scores at 5 years.

Intrauterine Growth and Cerebral Palsy in Twins: A European Multicenter Study

Population-based studies in twins have been of insufficient size to explore the relationship between risk of cerebral palsy and intrauterine growth. Earlier studies in singletons have suggested an optimum size at birth for minimum cerebral palsy risk between the 75th and 90th percentiles of weight for gestational age. We aggregated data from nine European cerebral palsy registers for 1976 to 1990. Using sex-specific fetal growth standards for twins, a z score of weight-for-gestation was derived for each of the 373 twin cases. The rates of cerebral palsy in each z-score band were compared to the rate in the a priori reference band of 0.67 to less than 1.28 (equivalent to the 75th to less than 90th percentiles). In twins born at 32 weeks' gestation or more (92% of all twins), cerebral palsy rates were higher for both light and heavy-forgestation babies compared to an optimum (i.e., minimum risk) in the reference band. However, the rate ratio for heavy babies (90th percentile or greater) did not reach conventional (95% confidence intervals [CI]) statistical significance (rate ratios = 1.76; 90% CI 1.02–3.03). For twins born at less than 32 weeks, the significantly higher risk for cerebral palsy was observed consistently in all z-score bands less than average compared to the reference band. This multi-center study demonstrates that for twins born at 32 weeks' gestation or more, an increased risk of cerebral palsy is associated with deviations from optimal intrauterine growth at about 1 standard deviation above mean weight, as was earlier reported for singletons. For twins born at less than 32 weeks' gestation, this pattern is only demonstrable for babies weighing below the optimum weight-for-gestation.

Single twin demise: consequence for survivors

Multiple pregnancies, the majority of which are twins, are at substantially higher risk of fetal morbidity and mortality when compared with singleton pregnancies. Single fetal demise occurs in up to 6.2% of all twin pregnancies. It may cause considerable risk for the co-twin including increased risk of fetal loss, premature delivery, neurovascular injury and end-organ damage. In this review we seek to summarise the most contemporary literature on the aetiology of single twin demise, the pathophysiology of injury to the surviving twin and the evidence for current management strategies.

Intra-uterine exposure to dual fetal programming sequences among surviving co-twins

OBJECTIVE

The dynamics of fetal programming following in utero demise of a co-twin are poorly understood.

METHODS

The authors examined fetal programming using a unique application of the change-point analysis method, and identified two types of fetal programming that occurred when a viable twin sibling died in utero, while the co-twin survived.

RESULTS

In one type, the initial twin fetal programming trajectory was maintained while in a subset of surviving co-twins a "switch" from a twin to a singleton fetal program (dual fetal programming exposure) was observed. The results suggest that the timing in utero of conversion from a twin to a singleton programming pattern occurred slightly earlier among opposite-sex than in same-sex surviving co-twins.

CONCLUSION

For the conversion from a twin to a singleton program to happen, the surviving co-twin must have attained a "critical mass" when the twin sibling died. Whereas, for same-sex surviving co-twins the critical mass for conversion was the 80th percentile of gestational-age specific birth weight, opposite-sex surviving co-twins converted at a lower critical mass (70th percentile). These novel findings warrant further study to confirm the new hithertofore unknown phenomenon of dual fetal programming sequence, and to determine the implications in terms of subsequent morbidity or mortality during infancy, childhood and adult life.

Twinning on the brain: the effect on neurodevelopmental outcomes

Twinning is currently considered a complex multifactorial trait. Few studies have explored how the unique genetic and environmental influences that create twinning affect phenotypes and outcomes. Previous data has shown that twins account for a significant proportion of preterm and low-birth-weight infants, who are at risk for long-term neurodevelopmental disabilities such as cerebral palsy and cognitive impairment. More recently, it has been postulated that even without these co-morbidities, twinning in and of itself may incur a neurodevelopmental disadvantage even among term newborns. The purpose of this review is to report primarily on neuromotor outcomes of twins compared to singletons. In addition, we describe specific environmental risk factors among twins which are associated with poorer outcomes. Several putative neurodevelopmental modulators are explored, including death of a co-twin, chorionicity, birth weight discordance, and twin-twin transfusion. By teasing out environmental influences that potentially influence neurocognitive outcomes, families can receive more specific counseling and developmental services can be provided to those twins at especially high risk.

Long-term health implications for children conceived by IVF/ICSI

In vitro fertilisation and intra-cytoplasmic sperm injection are well recognised techniques for assisted reproduction, helping over 85% of infertile couples conceive within a year, contributing to over 1% of the annual birth rate in the western world. There is currently limited data on the health of these children in later life as the techniques are relatively new. Certain trends have started to emerge with high order births proving to be responsible for a large proportion of premature and low-birth weight infants. The increased risk of perinatal morbidity and mortality associated with singleton births has been linked to the infertility of the couple rather than the techniques used. This theory has also been suggested to account for the increase in congenital malformations observed. No discrepancies in neurodevelopmental outcome of these children have been established and no detrimental psychological effects on the families have been reported. There has been an increase in childhood illness observed and the future fertility of these children is a major concern for many parents. Further follow up of these children is needed to fully establish the long-term health implications of in vitro fertilisation and intra-cytoplasmic sperm injection.

Neuropsychological screening of a group of preterm twins: comparison with singletons

OBJECTS

Perform neuropsychological screening of a group of preterm twins without major brain pathology and compare it with a control group of similarly preterm children born as singletons.

MATERIALS AND METHODS

Twenty-three preterm twins born at fewer than 32 weeks of gestation were tested for rapid evaluation of cognitive functions at the age of 4 years. The tests evaluated language, non-verbal performances, learning and attention deficit disorders. Cognitive profiles were established. Links between perinatal factors, clinical follow-up and cognitive outcome were investigated. Their cognitive outcome was then compared with the cognitive outcome of 31 preterm singletons with the same gestational periods.

CONCLUSION

The twins' neuropsychological outcome was not more marked than that of the singletons. Birth weight discordance and chorionicity were the only predictive perinatal factors with worse outcome in the twin population.

Outcome of assisted reproduction

In-vitro fertilisation has been done for nearly 30 years; in developed countries at least 1% of births are from assisted reproductive therapies (ART). These children now represent a substantial proportion of the population but little is known about their health. Some of the morbidity associated with ART does not result from the techniques but from the underlying health risks of being subfertile. Much of the amplified risk associated with ART is related to high birth order. However, risk of intrauterine and subsequent perinatal complications is enhanced after ART, and urogenital malformations can be present in boys, even in singleton infants. No increase in discord or other difficulties within families has been recorded. Long-term follow-up of children born after ART to reproductive age and beyond is necessary.

Prognosis for the co-twin following single-twin death: a systematic review

BACKGROUND

Following single-twin death, the perinatal mortality and morbidity for the surviving co-twin is increased but difficult to quantify. We present data on prognosis from a systematic review.

OBJECTIVES

We aimed to determine the incidence of a) co-twin death, b) neurological abnormality and c) preterm delivery for the surviving co-twin following single-twin death after 14 weeks of gestation.

SEARCH STRATEGY

Literature was identified by searching two bibliographical databases and specialist journals between 1990 and 2005.

SELECTION CRITERIA

The selected studies of > or = 5 cases reported on perinatal death and/or neurodevelopmental delay of the surviving co-twin.

DATA COLLECTION AND ANALYSIS

Studies were assessed for quality and data extracted to allow computation of rates. The data were inspected for heterogeneity using a Forrest plot and examined statistically using the chi-square test. Data from individual studies were pooled within subgroups defined by prognosis.

MAIN RESULTS

The search strategy yielded 632 potentially relevant citations. Full manuscripts were retrieved for 54 citations and 28 studies were finally included in the review. Following the death of one twin, the risk of monochorionic and dichorionic co-twin demise was 12% (95% CI 7-11) and 4% (95% CI 2-7), respectively. The risk of neurological abnormality in the surviving monochorionic and dichorionic co-twin was 18% (95% CI 11-26) and 1% (95% CI 0-7), respectively. The risk of preterm delivery was 68% (95% CI 56-78) and 57% (95% CI 34-77), respectively. Where there was comparative data within studies, the odds of monochorionic co-twin intrauterine death was six times that of dichorionic twins (OR 6.04 [95% CI 1.84-19.87]). Neurological abnormality was also higher in monochorionic compared with dichorionic pregnancies (OR 4.07 [95% CI 1.32-12.51]).

AUTHOR'S CONCLUSIONS

More prospective research is required to inform decision making on this subject, especially with data that allow stratification based upon chorionicity.

Risk of cerebral palsy in multiple pregnancies

Multiple compared with singleton gestations have a five- to tenfold increased risk of CP. The increased risk associated with MC placentation has been variously ascribed to transfer of thromboplastin or thromboemboli from the dead to the surviving fetus, exsanguination of the surviving fetus into the low pressure reservoir of the dead fetus, or hemodynamic instability with bidirectional shunting of blood between the two fetuses. An increased risk of CP in assisted reproductive technology gestations is to be expected because of the higher proportion of preterm births. The increase in risk of CP associated with monochorionic placentation will not be observed except for the minority of assisted reproductive technology gestations that undergo monozygotic splitting.

Regression models for clustered binary responses: implications of ignoring the intracluster correlation in an analysis of perinatal mortality in twin gestations

PURPOSE

Dependent binary responses, such as health outcomes in twin pairs or siblings, frequently arise in perinatal epidemiologic research. This gives rise to correlated data, which must be taken into account during analysis to avoid erroneous statistical and biological inferences.

METHODS

An analysis of perinatal mortality (fetal deaths plus deaths within the first 28 days) in twins in relation to cluster-varying (those that are unique to each fetus within a twin pregnancy such as birthweight) and cluster-constant (those that are identical for both twins within a sibship such as maternal smoking status) risk factors is presented. Marginal (ordinary logistic regression [OLR] and logistic regression using generalized estimating equations [GEE]) and cluster-specific (conditional and random-intercept logistic regression models) regression models are fit and their results contrasted. The United States "matched multiple data" file of twin births (1995-1997), which includes 285,226 twins from 142,613 pregnancies, was used to examine the implications of ignoring of clustering on regression inferences.

RESULTS

The OLR models provide variance estimates for cluster constant covariates that ranged from 7% to 71% smaller than those from GEE-based models. This underestimation is even more pronounced for some cluster-varying covariates, ranging from 21% to 198%.

CONCLUSIONS

Ignoring the cluster dependency is likely to affect the precision of covariate effects and consequently interpretation of results. With widespread availability of appropriate software, statistical methods for taking the intracluster dependency into account are easily implemented and necessary.

Risk of cerebral palsy in multiple pregnancies

Multiple compared with singleton gestations have a five- to tenfold increased risk of CP. The increased risk associated with MC placentation has been variously ascribed to transfer of thromboplastin or thromboemboli from the dead to the surviving fetus, exsanguination of the surviving fetus into the low pressure reservoir of the dead fetus, or hemodynamic instability with bidirectional shunting of blood between the two fetuses. An increased risk of CP in assisted reproductive technology gestations is to be expected because of the higher proportion of preterm births. The increase in risk of CP associated with monochorionic placentation will not be observed except for the minority of assisted reproductive technology gestations that undergo monozygotic splitting.

Do multiple gestations raise the risk of cerebral palsy?

There is an increased risk of CP in multiple as compared with singleton pregnancies, and the higher the number of fetuses the greater is the prevalence of CP. Although LBW and preterm birth are the most significant risk factors for CP, the disadvantage of twins is apparent near term. Moreover, the excessive risk is not only the result of over-representation of multiples among premature babies, but seems to be associated with circumstances that are unique to the twinning process. The risk of CP should be acknowledged not only when a multiple pregnancy is diagnosed, but also when counseling infertility patients in whom iatrogenic multiple pregnancies are an actual risk.

Cerebral palsy in triplet pregnancies with and without iatrogenic reduction

Iatrogenic fetal reduction is undertaken to try and improve the outcome of multiple pregnancies by reducing the rate of severe preterm delivery. In twin pregnancies, however, spontaneous death of one of the fetuses is associated with increased risk of cerebral palsy (CP) in the survivor. The aim of this study was to determine whether iatrogenic fetal reduction might also increase the prevalence of CP. The database of a tertiary fetal medicine unit was interrogated to identify women with trichorionic triplet pregnancies who had either given birth to three live infants or two live infants following selective fetal reduction. A questionnaire was sent to the women's general practitioners asking them to report whether any of the children had CP. The results of the questionnaire revealed that the CP prevalence (13.8 per 1000) of 72 children from trichorionic triplet pregnancies reduced to twins by selective termination was similar to that of 111 children from trichorionic triplet pregnancies with no loss (18 per 1000), but the pregnancies with selective termination delivered at a later gestation (P = 0.004).

CONCLUSION

a lower cerebral palsy rate might have been expected in the pregnancies with selective termination given that they were delivered at a later gestational age; these data, therefore, emphasise the importance of further investigating the impact of selective reduction on the prevalence of cerebral palsy.

Development of a real-time PCR and a sandwich ELISA for detection of potentially allergenic trace amounts of peanut (Arachis hypogaea) in processed foods

Hidden allergens in food products are, especially for peanut-allergic consumers, a serious problem because even low amounts (approximately 200 microg) of peanut can elicit allergic reactions. Undeclared peanut traces can be found in processed food products, because contaminations with peanut during production processes are frequent. To minimize the risk of such cross-contaminations, it is necessary to develop sensitive analytical methods for the detection of hidden allergens in foods. For this approach we developed two peanut-specific assays based on the detection of peanut protein by specific antibodies (sandwich ELISA) and by the detection of peanut-specific DNA (part of the coding region of Ara h 2) by a real-time PCR. Both tests did not show any cross-reactivity with 22 common food ingredients (cereals, nuts, legumes), and the limit of detection is <10 ppm peanut in processed foods. Thirty-three random samples of food products were tested for the presence of peanut to compare both assay types with each other and to evaluate the percentage of foods on the German market that are contaminated with peanut traces. We found that four products (13.3%) without peanut in the list of ingredients contained peanut protein in a range from 1 to 74 ppm peanut protein and that the results of both tests correlated well. The real-time PCR was able to detect one more positive sample than the sandwich ELISA. In conclusion, both assays are sensitive and specific tools for the detection of hidden allergens in processed foods.

Long-term neurodevelopmental outcome in twin-to-twin transfusion syndrome

OBJECTIVE

The purpose of this study was to determine the long-term neurodevelopmental outcome in children after twin-to-twin transfusion syndrome.

STUDY DESIGN

Maternal and neonatal medical records of all twin-to-twin transfusion syndrome patients who were admitted to our center between 1990 and 1998 were reviewed. Neurologic and mental development at school age was assessed during a home visit in all twin-to-twin transfusion syndrome survivors.

RESULTS

A total of 33 pregnancies with twin-to-twin transfusion syndrome were identified. Four couples opted for termination of pregnancy. All other pregnancies were treated conservatively, 18 pregnancies (62%) with serial amnioreductions and 11 pregnancies (38%) without intrauterine interventions. Mean gestational age at delivery was 28.6 weeks (range, 20-37 weeks). The perinatal mortality rate was 50% (29/58 infants). The birth weight of the donor twins was less than the recipient twins (P<.001). Systolic blood pressure at birth was lower in donors than in recipients (P=.023), and donors required inotropic support postnatally more frequently than did recipients (P=.008). The incidence of hypertension at birth was higher in recipients than in donors (P=.038). Abnormal cranial ultrasonographic findings were reported in 41% of the neonates (12/29 neonates). All long-term survivors (n=29 neonates) were assessed during a home visit. Mean gestational age at birth of the surviving twin was 31.6 weeks (range, 25-37 weeks). The mean age at follow-up was 6.2 years (range, 4-11 years). The incidence of cerebral palsy was 21% (6/29 infants). Five of 6 children with cerebral palsy had an abnormal mental development. The incidence of cerebral palsy in the group of survivors who were treated with serial amnioreduction was 26% (5/19 infants). Four children were born after the intrauterine fetal demise of their co-twin, 2 of which had cerebral palsy.

CONCLUSION

The incidence of adverse neurodevelopmental outcome in twin-to-twin transfusion syndrome survivors is high, especially after the intrauterine fetal demise of a co-twin.

Monochorionic diamniotic twins: complications and management options

PURPOSE OF REVIEW

Monochorionic compared with dichorionic twins have disproportionately high fetal loss rates, perinatal mortality and morbidity. This is because of the unpredictable vascular anastomoses and the often asymmetrical distribution of the single placenta between both twins.

RECENT FINDINGS

The pathophysiology of twin-to-twin transfusion syndrome is usually explained on an angioarchitectural basis, although certain hemodynamic and hormonal factors also may be involved. The results of the large randomized trials on amnioreduction, fetoscopic laser coagulation and septostomy are still awaited. An update is given on hardware and instruments required for fetoscopic laser. Subsequently, the problem of the monochorionic twin set with severe early discordant growth is addressed. Several etiological mechanisms have been proposed, but little is known of its natural history. Also, umbilical artery Doppler waveforms may not have the same predictive value as in singletons. Prophylactic laser coagulation of the vascular anastomoses to protect against the adverse effects of single intrauterine demise, has so far not been shown to confer any benefit in outcome. Finally, pathophysiology and management of discordant structural and chromosomal anomalies in monochorionic twins are discussed. Laser and monopolar coagulation, which can be introduced through a needle, may be used for selective feticide in early pregnancy or low hemodynamic conditions. Bipolar coagulation seems more effective at later gestational ages and normal hemodynamic conditions.

SUMMARY

Our insight into the complications associated with monochorionic twins has increased in recent years. It is hoped that this will lead to better surveillance and ultimately an improved outcome for these high-risk pregnancies.

Clinical dilemma in triplet pregnancy: when is it appropriate to intervene for a jeopardized fetus?

OBJECTIVE

To determine gestational age-specific risks of intervening to "rescue" a compromised fetus in triplet pregnancies.

STUDY DESIGN

We analyzed retrospectively triplet pregnancies managed at New England Medical Center (July 1992-May 2000; n=97 pregnancies). For each week in gestation, we compared the chance of at least one of three infants developing complications of prematurity in Scenario A (delivery at that gestation to rescue the jeopardized fetus) with the chance of at least one of two infants from Scenario B (allowing the jeopardized fetus to die in utero to prolong pregnancy) developing that complication later in gestation.

RESULTS

We observed a decreased risk of at least one infant developing a specific complication in Scenario B than in Scenario A for all complications studied.

CONCLUSIONS

Comparison of triplet outcomes with the two surviving older newborns identifies important changes in risk between 25 and 32 weeks. These data enable physicians and parents to weigh acceptable risks with benefits.

Cerebral palsy in twins: a national study

BACKGROUND

Cerebral palsy is more common in twins than singletons. Among twins, if one twin suffers a fetal death or dies in infancy, the prevalence of cerebral palsy in the surviving co-twin is considerably increased, and those from like-sex pairs are particularly at high risk.

AIM

To compare birthweight specific cerebral palsy prevalence in like-sex and unlike-sex twins where both twins survive infancy and to provide a comparative and composite picture of cerebral palsy prevalence according to whether a co-twin died or where both twins survived.

METHODS

Parents of twins born in England and Wales in 1994 and 1995 completed a booklet with open ended questions asking whether their twins had any medical, physical, visual, genetic, or chromosomal problems. Any mention of cerebral palsy, hemiplegia, diplegia, or quadriplegia allowed the child to be included as a case of cerebral palsy. Birthweight specific prevalence rates of cerebral palsy were determined for like and unlike-sex twins in birthweight groups < 1000 g, 1000-1499 g, 1500-1999 g, 2000-2499 g, and > or = 2500 g.

RESULTS

When both twins survived infancy, like-sex were at greater risk of cerebral palsy than unlike-sex twins, but the difference was not statistically significant. If both twins survived infancy, the birthweight specific prevalence of cerebral palsy was significantly less than if the co-twin had died.

CONCLUSIONS

Among the generality of twins, like-sex compared with unlike-sex twins are at greater risk of cerebral palsy particularly if one twin suffers a fetal or infant death. Although it is not possible to subdivide the twins according to zygosity, it is postulated that monozygosity and, specifically, monochorionicity may be the crucial feature that leads to the higher prevalence of cerebral impairment among like-sex twins.

Neonatal and long-term outcomes of very low birth weight infants from single and multiple pregnancies

The revolution in artificial reproductive technologies has resulted in a dramatic rise in the incidence of multiple pregnancies. Many of these infants are born prematurely, often extremely so. Consequently, perinatal morbidity and mortality are highly correlated with plurality. The primary mechanism for this increased risk is prematurity. Studies of the relationship between plurality and outcome are frequently hampered by major differences in case mix between singletons, twins and high multiples. For example, high multiples tend to receive earlier prenatal care, receive more antenatal steroids, are more often delivered by Caesarean section and more often suffer from respiratory distress syndrome. However, recent studies that appropriately account for relevant confounding variables have suggested that very low birth weight infants from high multiple pregnancies are at excess risk for mortality when compared with twins and singletons. This article reviews the current available evidence.