A hypothesis for the aetiology of spastic cerebral palsy--the vanishing twin

Current approach to cerebral palsy

This teaching review aims to provide an overview of the current approach to children with cerebral palsy (CP), retrieving the best available evidence and summarizing existing knowledge in the field of CP in children. We also highlight areas where more research is needed and novel strategies for diagnosing and treating cerebral palsy. CP includes a group of permanent disorders of movement and posture that cause activity limitation. Multiple risk factors, occurring preconceptionally, prenatally, perinatally, or postneonatally, are involved in the pathogenesis of CP, with the prenatal ones accounting for 80-90 % of cases. Due to its heterogeneity, CP has various classifications, but usually is classified based on clinical findings and motor impairment. Standardized function classification systems have been developed to address inconsistencies in previous classifications. The combination of clinical assessment and validated predictive tools is recommended for an early diagnosis, which is important for early intervention and prevention of secondary impairments. The therapeutic regimen in CP involves prevention and management of the motor and associated problems. It includes the enhancement of motor performance, the enrichment of cognition and communication skills, the prevention of secondary impairments, and the support of parents and caregivers. The care of CP children demands a multidisciplinary approach focused on improving motor skills, reducing comorbidities, enhancing the quality of life, and prolonging survival.

Association Between Assisted Reproductive Technology and Cerebral Palsy: A Meta-Analysis

BACKGROUND

Since 1978 many children are born thanks to assisted reproductive technology (ART). However, the long-term effects of these therapies are still not fully known. Our objective is to evaluate the risk of cerebral palsy (CP) after ART compared with that in those spontaneously conceived (SC) and to examine this risk in single, multiple, and preterm births and the evolution of the risk over the years.

METHODS

PubMed, Embase, and Web of Science databases were searched until December 2022. Studies were included if they studied CP cases in children born through ART. 16 studies were finally selected. Quality of studies was assessed using Newcastle Ottawa Scale. Pooled OR was estimated by weighting individual OR/RR by the inverse of their variance. A random-effect model was applied. To assess the causes of heterogeneity, we performed meta-regression analyses.

RESULTS

A significantly high risk of CP was found (OR = 1.27; 95% CI 1.12 to 1.43) in children born through ART compared with those SC. This risk increased in singletons (OR = 1.48; 95% CI 1.23 to 1.79) but disappeared in multiple (OR = 1.05; 95% CI 0.93 to 1.18) and preterm births (OR = 1.09; 95% CI 0.87 to 1.37). We found a higher risk of CP in children born before the year 2000 (OR = 3.40; 95% CI 2.49 to 4.63).

CONCLUSIONS

ARTs slightly increase the risk of CP once the effect of multiple gestation is controlled. Further studies are needed to clarify whether the techniques themselves, fertility problems, or associated maternal comorbidities are responsible for this risk.

Clinical outcomes of vanishing twin syndrome and selective fetal reduction after double embryos transferred in IVF pregnancy: A propensity score matching study

OBJECTIVE

The purpose of this study was to analyze the influence of early vanishing twin syndrome (VTS) and selective fetal reduction (SEFR) on surviving singleton births in in-vitro fertilization (IVF) pregnancy.

METHODS

We collected patients who conceived through IVF and delivered singletons over the past six years. The VT group (n = 194) and SEFR group (n = 144) had underwent double embryos transferred (DET) and only one fetus was born, due to the subsequent one birth reduction. The SET group had one embryo transferred (SET) and gave birth to singleton. Using the propensity score matching (PSM) method to reduce confounding, the VT group and SEFR group were matched and compared with 570 and 576 singleton controls, respectively (SET-I/II group). Obstetric complications and neonatal outcomes were compared. In addition, quantity and quality of transferred embryos of VT (n = 194) and singleton groups (born with singleton after DET and matched with VT group by PSM, n = 554) were compared.

RESULTS

Compared with the SET-I group, VT group had increased incidence of severe obstetric complications, including severe preeclampsia (p = 0.031), oligohydramnios (p = 0.038) and polyhydramnios (p = 0.015). VT group was more likely to show more frequent small for gestational age (SGA) (p = 0.046) and very small for gestational age (VSGA) (p = 0.031). Newborns in the SEFR group had a significantly lower birth weight (p = 0.005) and were more likely to manifest as low birthweight (LBW) (p = 0.009) and very low birthweight (VLBW, birth weight < 1500 g) (p = 0.012), and the incidence of very large for gestational age (VLGA) was lower (p = 0.030), compared with the control group. There were more developmental abnormalities in newborns of VTS, for decreased incidence of SGA (OR 0.156, 95% CI 0.036-0.669), VSGA (OR 0.057, 95% CI 0.006-0.553) and VLGA (OR 0.415, 95% CI 0.212-0.815) in SEFR group. The good quality embryo rate was higher in VT group (72.7% vs. 63.3%, p = 0.001) compared with the singleton group.

CONCLUSIONS

DET with subsequent VTS/SEFR carried a higher rate of adverse clinical outcomes, and the VTS group had worse perinatal outcome compared with SEFR. Therefore, we recommend SET in ART.

Cerebral palsy in ART children has declined substantially over time: a Nordic study from the CoNARTaS group

STUDY QUESTION

Are the decreasing multiple birth rates after ART associated with a simultaneous drop in the incidence of cerebral palsy (CP) in ART children over time?

SUMMARY ANSWER

The relative odds of CP in ART children have declined in the Nordic countries over the past two decades concurrently with declining multiple birth rates.

WHAT IS KNOWN ALREADY

In the Nordic countries, the rate of twin pregnancies after ART has decreased from 30% in the early 1990s to 4-13% in 2014, following the implementation of elective single embryo transfer (SET). Consequently, preterm birth rates have declined substantially in ART pregnancies. However, whether the risk of CP, a known consequence of preterm birth, has decreased correspondingly is still unknown.

STUDY DESIGN, SIZE, DURATION

Retrospective register-based cohort study based on data on all singletons, twins, and higher-order multiples born in Denmark (birth year 1994-2010), Finland (1990-2010), and Sweden (1990-2014), corresponding to 111 844 ART children and 4 679 351 spontaneously conceived children.

PARTICIPANTS/MATERIAL, SETTING, METHODS

Data were obtained from a large Nordic cohort of children born after ART and spontaneous conception initiated by the Committee of Nordic ART and Safety-CoNARTaS. The CoNARTaS cohort was established by cross-linking national register data using the unique personal identification number, allocated to every citizen in the Nordic countries. Data from the National Medical Birth Registers, where information on maternal, obstetric, and perinatal outcomes is recorded, were cross-linked to data from the National ART- and Patients Registers to obtain information on fertility treatments and CP diagnoses. Relative risks of CP for ART compared to spontaneous conception were estimated as odds ratios from multivariate logistic regression analyses across all birth years, as well as for the following birth year categories: 1990-1993, 1994-1998, 1999-2002, 2003-2006, 2007-2010, and 2011-2014. Analyses were made for all children and for singletons and twins, separately.

MAIN RESULTS AND THE ROLE OF CHANCE

The main outcome measure was the relative odds of CP in different time periods for ART versus spontaneously conceived children. CP was diagnosed in 661 ART children and 16 478 spontaneously conceived children born between 1990 and 2014. In 1990-1993, the relative odds of CP were substantially higher in all ART children (adjusted odds ratio (aOR) 2.76 (95% CI 2.03-3.67)) compared with all spontaneously conceived children, while in 2011-2014, it was only moderately higher (aOR 1.39 (95% CI 1.01-1.87)). In singletons, the higher relative odds of CP in ART children diminished over time from 1990 to 1993 (aOR 2.02 (95% CI 1.22-3.14)) to 2003-2006 (aOR 1.18 (95% CI 0.91-1. 49)) and was not significantly increased for birth cohorts 2007-2010 and 2011-2014. For ART twins versus spontaneously conceived twins, the relative odds of CP was not statistically significantly increased throughout the study period.

LIMITATIONS, REASONS FOR CAUTION

The main limitation of the study was a shorter follow-up time and younger age at first CP diagnosis for ART children compared with spontaneously conceived children. However, analyses ensuring a minimum of bias from differences in age at CP diagnosis and follow-up time confirmed the results, hence, we do not consider this to cause substantial bias.

WIDER IMPLICATIONS OF THE FINDINGS

A SET policy in ART treatments has the potential to reduce the increased risk of cerebral palsy in the ART population due to lower rates of multiple deliveries. At a time with high survival rates of frozen/thawed embryos, this study provides a strong argument against the continued use of multiple embryo transfer in most ART settings. Larger cohort studies including also the number of gestational sacs in early pregnancy will be preferable to show an effect of vanishing twins on the risk of CP in the ART population.

STUDY FUNDING/COMPETING INTEREST(S)

The study was financed by grants from NordForsk (grant number 71450), Elsass Foundation (19-3-0444), the ALF-agreement (ALFGBG 70940), and The Research Fund of Rigshospitalet, Copenhagen University Hospital. There are no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

ISRCTN11780826.

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.

The complex aetiology of cerebral palsy

Cerebral palsy (CP) is the most prevalent, severe and costly motor disability of childhood. Consequently, CP is a public health priority for prevention, but its aetiology has proved complex. In this Review, we summarize the evidence for a decline in the birth prevalence of CP in some high-income nations, describe the epidemiological evidence for risk factors, such as preterm delivery and fetal growth restriction, genetics, pregnancy infection and other exposures, and discuss the success achieved so far in prevention through the use of magnesium sulfate in preterm labour and therapeutic hypothermia for birth-asphyxiated infants. We also consider the complexities of disentangling prenatal and perinatal influences, and of establishing subtypes of the disorder, with a view to accelerating the translation of evidence into the development of strategies for the prevention of CP.

A review of the mechanisms and evidence for typical and atypical twinning

The mechanisms responsible for twinning and disorders of twin gestations have been the subject of considerable interest by physicians and scientists, and cases of atypical twinning have called for a reexamination of the fundamental theories invoked to explain twin gestations. This article presents a review of the literature focusing on twinning and atypical twinning with an emphasis on the phenomena of chimeric twins, phenotypically discordant monozygotic twins, mirror-image twins, polar body twins, complete hydatidiform mole with a coexistent twin, vanishing twins, fetus papyraceus, fetus in fetu, superfetation, and superfecundation. The traditional models attributing monozygotic twinning to a fission event, and more recent models describing monozygotic twinning as a fusion event, are critically reviewed. Ethical restrictions on scientific experimentation with human embryos and the rarity of cases of atypical twinning have limited opportunities to elucidate the exact mechanisms by which these phenomena occur. Refinements in the modeling of early embryonic development in twin pregnancies may have significant clinical implications. The article includes a series of figures to illustrate the phenomena described.

Cerebral palsy

The syndrome of cerebral palsy encompasses a large group of childhood movement and posture disorders. Severity, patterns of motor involvement, and associated impairments such as those of communication, intellectual ability, and epilepsy vary widely. Overall prevalence has remained stable in the past 40 years at 2-3·5 cases per 1000 livebirths, despite changes in antenatal and perinatal care. The few studies available from developing countries suggest prevalence of comparable magnitude. Cerebral palsy is a lifelong disorder; approaches to intervention, whether at an individual or environmental level, should recognise that quality of life and social participation throughout life are what individuals with cerebral palsy seek, not improved physical function for its own sake. In the past few years, the cerebral palsy community has learned that the evidence of benefit for the numerous drugs, surgery, and therapies used over previous decades is weak. Improved understanding of the role of multiple gestation in pathogenesis, of gene environment interaction, and how to influence brain plasticity could yield significant advances in treatment of the disorder. Reduction in the prevalence of post-neonatal cerebral palsy, especially in developing countries, should be possible through improved nutrition, infection control, and accident prevention.

Psychological Vulnerability of Singleton Children After the ‘Vanishing’ of a Co-Twin Following Assisted Reproduction

We test the hypothesis that parents who conceived twins by assisted reproduction technology (ART), but experienced loss of one twin, have a different parental–child relationship compared with ART parents following a singleton pregnancy. We used the 1994–2005 ART database of the Centre for Infertility of the Arcispedale Santa Maria Nuova in Reggio Emilia, Italy to identify families of 53 singleton births after the ‘vanishing’ twin syndrome. The controls comprised 106 families who conceived and delivered singletons, matched for gestational age (≥ 28 ≤ 31, ≥ 32 ≤ 36, ≥ 37 weeks), maternal age (< 35, ≥ 35 ≤ 40, > 40 years), child's age (1–3, 4–6, and 7–11 years) and child's gender. We completed 3 tests: a sociodemographic questionnaire, the QUIT — Italian Questionnaires of Temperament — motor scale, and the Child Vulnerability Scale. We found that children in the study had significantly more difficulties at the beginning of nursery school (p = .002) and kindergarten (p = .0005), with more frequent anxiety of separation from the parents (nursery school, p = .009; kindergarten, p = .001). We found a lower mean QUIT motor score for the 7- to 11-year-old children when compared to the general Italian normative values, suggesting that parents perceived their children as having more motor difficulties. In contrast, analysis of the Child Vulnerability Scale showed that significantly more parents (15.1%) from the controls perceived their child as vulnerable compared to those from the study group (3.8%), p = .034. We conclude that despite the perceived motor difficulties and the difficulties in the process of individuation–separation that appear at the beginning of the different educational circumstances, parents of singletons following the ‘vanishing’ twin syndrome perceive their children as ‘invincible’, and thus less vulnerable compared to controls.

Errors in Birth Registrations and Coding of Twins and Higher Order Multiples

Dizygotic compared with monozygotic conceptions are at decreased risk of fetal and infant death and serious morbidity in surviving infants. Different sex twin maternities must be dizygotic but miscoding and incorrect registration of sex and number of fetuses may lead to an incorrect assignment of zygosity. The aim of the study was to validate the coding and registration of number and sex of births in multiple pregnancies. Fetal and infant death registrations from all multiple maternities in England and Wales 1993–1998 were examined. There were 51,792 twin, 1627 triplet and 51 higher order multiple maternities that were registered. Among these there were 1926 fetal deaths, 58 of which were registered as being of indeterminate sex but were coded as male in 56 and female in 2 cases. A fetus papyraceous was registered as male in 19 and as female in 19 cases. Other fetal deaths weighing ≤100g, with no mention of papyraceous on the death certificate, nevertheless, likely to be of indeterminate sex, were registered as male in 26 and as female in 23 cases. In 13 maternities, the number of infants registered at birth was less than the number mentioned on the registration certificate. It cannot be assumed that multiple births of different registered sex are dizygotic. As surviving infants from a monozygotic multiple birth are at much greater risk of infant death and serious morbidity than dizygotic multiple births, incorrect assignment of sex has important implications for parental counselling and may have medicolegal relevance when attributing negligence as the cause of morbidity in a survivor from a multiple pregnancy.

Vanishing Twin: A Possible Cause of Cerebral Impairment

Fetal death in a twin conception during second and third trimester is associated with increased risk of cerebral injury in the surviving twin. The aim of this study is to test the hypothesis that even early fetal losses as a ‘vanishing’ twin may be associated with an increased risk of cerebral impairment in the surviving twin. The study population comprised 362 pregnant women attending Liverpool Women's Hospital recruited between 1999 and 2001. Women were classified according to the first ultrasound scan into 3 groups: vanishing twin, twin and singleton. The vanishing twin group was further subdivided into ‘definite’ and ‘probable’. Children from these pregnancies were assessed at 1 year of age for their development and neurological function using the Griffiths Mental and Developmental Scales and Optimality score. Children from 229 pregnancies (63.2%) attended the assessment. Information on children from a further 21 (5.8%) pregnancies was obtained through a review of hospital records. Cerebral impairment was found in 2 children from the vanishing twin group, 2 from the twin group and none from the singleton group. When cases with definite vanishing twin are considered there is a significant difference between the vanishing twin and singleton group (relative risk 6.1; 95% confidence interval 1.5–8.3; p = .03). An additional study with an increased sample size would enable a more robust conclusion.

Causal Hypothesis for Some Congenital Anomalies

Congenital anomalies are a major cause of fetal and neonatal death and of childhood morbidity. Chromosomal and other genetic abnormalities, environmental teratogens and some nutritional deficiencies account for some congenital anomalies but the majority are of unknown etiology. The hypothesis is here proposed that a significant proportion of congenital anomalies and cerebral palsy of unknown etiology are attributable to a monozygotic multiple conception with monochorionic placentation and that these anomalies, even in singletons, may be explained by early, unrecognized or unrecorded loss of one conceptus in a monochorionic monozygotic conception. The pathological mechanism is hemodynamic instability with episodes of acute feto–fetal transfusion that produce ischemic organ impairment in either or both twins. The resultant clinical abnormality will depend on range of severity (fetal death, infant death, congenital anomaly, normal infant), site or combination of sites (which organ[s] present[s] with the congenital anomaly) and timing (early, middle or late in gestation as shown by variation in brain pathology that is observed).

Why are monozygotic twins different?

Although popularly designated as "identical", monozygotic (MZ) twins are rarely identical. Much has been speculated on the origin of MZ twins and several theories have been proposed. Post-fertilization events, such as chromosomal mosaicism, skewed X-inactivation and imprinting mechanisms, as well as other epigenetic mechanisms are responsible for the differences between MZ twins. Numerous discordant MZ twins have been reported including discordance for lateral asymmetry, major malformation, growth and intrauterine death of the co-twin. This discrepancy may have long-term implications on complex diseases and their predisposition, organ transplantation and interpretation of twin-based studies. We reviewed the genotypic and phenotypic differences between MZ twins and discuss their main causes.

Cerebral palsy and assisted reproductive technologies: a case-control study

AIM

To determine whether assisted reproductive technologies (ART) were more likely to be the method of conception in singletons with cerebral palsy (CP) than in those without CP.

METHOD

Singletons with CP born between 1991 and 2004 were selected from the Victorian Cerebral Palsy Register and matched for birth year to two singletons randomly selected from the Victorian Perinatal Data Collection Unit. Data from both sources were linked to records from three ART centres. Conditional logistic regression was used to assess the association between CP and aspects of conception using ART. Multivariate models were adjusted for parity, previous miscarriages, sex, gestational age, birthweight, and weight for gestational age.

RESULTS

We identified 1241 singletons with CP (males n=721 [58%], females n=420 [42/100]; motor type: spastic [87%; unilateral 37%; bilateral 63%], ataxic n=60 [5/100], dyskinetic n=46 [4/100], hypotonic n=29 [2/100], unknown n=25 [2/100]. Gross Motor Function Classification System levels were I n=363 [29/100], II n=297 [24/100], III n=137 [11/100], IV n=160 [13/100], V n=192 [15/100], and unknown n=92 [7/100]). Sixteen (1.3/100) of the children with CP and 25 (1.0/100) of 2482 children without CP were conceived using ART. There was no significant increase in the odds of children with CP being conceived using ART (adjusted odds ratio 1.19, 95% confidence interval (CI) 0.63, 2.24) nor in the odds of them being conceived by a subfertile couple without ART (adjusted odds ratio 2.7, 95% CI 0.87, 8.36).

INTERPRETATION

Singleton conception using ART is not strongly associated with an increased risk of CP.

Congenital anomalies in children with cerebral palsy: a population-based record linkage study

AIM

Our aim was to determine the proportion of children with cerebral palsy (CP) who have a congenital anomaly (CA) in three regions (Isère Region, French Alps; Funen County, Denmark; Northern Region, England) where population-based CP and CA registries exist, and to classify the children according to CA subtype.

METHOD

Data for children born between 1991 and 1999 were linked using electronic matching of cases. All potential matches were checked manually by each centre and verified as true matches.

RESULTS

A total of 1104 children with CP were born during the study period (663 males, 441 females). Of these, 166 (15%; 95% Confidence Interval [CI] 13.0-17.3) children with CP had a CA: 8.8% had a cerebral anomaly, 4.8% had a non-cerebral anomaly, and 1.4% had a non-cerebral-related syndrome or a chromosomal/genetic anomaly.

INTERPRETATION

The prevalence of cerebral anomaly was highest in children with ataxic CP (41.7%) and lowest in those with dyskinetic CP (2.1%). Cerebral anomalies were found in 8.4% and 7% of children with bilateral and unilateral spastic CP respectively. The most frequent cerebral anomalies were primary microcephaly (26.5%) and congenital hydrocephalus (17.3%). The most common non-cerebral anomalies recorded were cardiac (12.6% of children with CP and CA), urinary (5.4%), and musculoskeletal (5.4%). The prevalence of cerebral anomalies was higher among children born at term (13%) than among those born preterm (3.8%). Associated sensorineural or intellectual impairments occurred more often in children with CP and cerebral anomalies. We concluded that cerebral and non-cerebral CA prevalence was higher among the CP population than in the general population of live births.

The risk of cerebral palsy in survivors of multiple pregnancies with cofetal loss or death

OBJECTIVE

This study investigated the risks for cerebral palsy in survivors of multiple pregnancies with cofetal loss (< 20 weeks' gestation) or cofetal death (>or= 20 weeks' gestation).

STUDY DESIGN

The total Western Australian population-based case-control study included 741 cases of cerebral palsy.

RESULTS

Antenatal cofetal loss or death occurred in 3% of all cases of cerebral palsy, which is a small but significant contribution. The odds ratio for cerebral palsy in survivors of cofetal loss that included iatrogenic pregnancy reduction was 2.65 (95% confidence interval [CI], 0.78-8.98), which gave a population-attributable proportion of 7.28% (95% CI, 0-27.5), compared with 4.25 (95% CI, 1.12-16.10) and 10.6% (95% CI, 1.0-35.6) for survivors of cofetal death.

CONCLUSION

This study quantifies the contribution of cofetal death to cerebral palsy and suggests that cofetal loss makes a similar, although somewhat smaller, contribution to the risk for cerebral palsy in survivors of multiple pregnancies.

Congenital anomalies in multiple births after early loss of a conceptus

BACKGROUND

Congenital anomalies are more common in twins than singletons but in the majority, aetiology is not known. Our aim was to test the hypothesis that survivors of an early loss in a multiple conception, compared with all singletons, are at increased risk of congenital anomaly.

METHODS

Data were abstracted from the UK population-based Northern Multiple Pregnancy Register and Northern Congenital Abnormality Survey, 1998-2004.

RESULTS

Among 3311 twin conceptions, both conceptuses were lost at <16 weeks gestation in 67, and one conceptus in 142 conceptions. Of the 142 singleton survivors, two died in infancy, two were terminated for a congenital anomaly and 11 of 138 had a congenital anomaly (prevalence 915.5 per 10,000 births). There were 197 congenital anomalies among 5948 registered twin births (331.2 per 10,000). The relative risk (RR) of congenital anomalies in a singleton with early loss of a conceptus and twins was 2.40 [95% confidence interval (CI): 1.34-4.29]. There were 4265 infants with a congenital anomaly among the 206 914 singletons [206.1 per 10,000 births: RR twin:singleton 1.61 (95% CI 1.40-1.89)].

CONCLUSIONS

A highly significant increase in the risk of congenital anomaly in survivors from a multiple conception following early loss of a conceptus supports the hypothesis that many congenital anomalies are associated with monozygotic multiple conceptions.

Prevalence and pathogenesis of congenital anomalies in cerebral palsy

BACKGROUND

It has been hypothesised that cerebral palsy (CP) and other congenital anomalies are attributable to feto-fetal transfusion problems in a monochorionic multiple gestation. Thus more than one organ could be compromised leading to the coexistence of two or more anomalies in a fetus. Such anomalies in a singleton birth may be attributable to early demise of the co-conceptus as a vanishing twin.

AIM

To determine whether the coexistence of congenital anomalies and CP is greater than a chance finding by comparing the prevalence of congenital anomalies in children with CP with that in the general population of children.

METHODS

A population-based register of children with CP born in 1966-1991 in the counties of Merseyside and Cheshire, UK, comprised the index population. Coexisting congenital anomalies were recorded. For comparison the population prevalence of congenital anomalies was obtained from eight congenital malformation registers in the UK.

RESULTS

Children with CP were found to have highly significant increases in risk for microcephaly, isolated hydrocephaly, congenital anomalies of the eye, congenital cardiac anomalies, cleft lip and/or palate and congenital dislocation of the hips and talipes (p<0.001) and atresias of the oesophagus (p<0.001) and intestines (p<0.01). The relative risks ranged from 3.1 (95% CI 1.9 to 4.8; p<0.001) for congenital malformations of the cardiac septa to 116.09 (95% CI 84.0 to 162.3; p<0.001) for microcephaly.

CONCLUSIONS

Congenital anomalies in children with CP are found much more frequently than expected by chance. A common pathogenic mechanism may account for the coexistence of disparate congenital anomalies. A hypothesis is proposed for such a common pathogenic mechanism.

Cerebral palsy among children born after in vitro fertilization: the role of preterm delivery--a population-based, cohort study

OBJECTIVE

Our aim was to assess the incidence of cerebral palsy among children conceived with in vitro fertilization and children conceived without in vitro fertilization.

METHODS

A population-based, cohort study, including all live-born singletons and twins born in Denmark between January 1, 1995, and December 31, 2000, was performed. Children conceived with in vitro fertilization (9255 children) were identified through the In Vitro Fertilization Register; children conceived without in vitro fertilization (394,713) were identified through the Danish Medical Birth Register. Cerebral palsy diagnoses were obtained from the National Register of Hospital Discharges. The main outcome measure was the incidence of cerebral palsy in the in vitro fertilization and non-in vitro fertilization groups.

RESULTS

Children born after in vitro fertilization had an increased risk of cerebral palsy; these results were largely unchanged after adjustment for maternal age, gender, parity, small-for-gestational age status, and educational level. The independent effect of in vitro fertilization vanished after additional adjustment for multiplicity or preterm delivery. When both multiplicity and preterm delivery were included in the multivariate models, preterm delivery remained associated strongly with the risk of cerebral palsy.

CONCLUSIONS

The large proportions of preterm deliveries with in vitro fertilization, primarily for twins but also for singletons, pose an increased risk of cerebral palsy.

Cerebral palsy and intrauterine growth

When birth weight for gestation is used as a surrogate for intrauterine growth, the prevalence of cerebral palsy varies continuously in a reversed J shape, with steep increases in the risk for infants lighter and heavier than the optimum size. Patterns of size-at-birth specific risk for cerebral palsy differ between male and female infants, as do the patterns for more severe versus milder cases. Although these excess risks with abnormal size at birth imply antenatal precursors, it is not clear whether or how intrauterine growth is involved in any of the suspected causal pathways resulting in cerebral palsy. The implication for clinicians is that serial measures of in utero growth may provide an important indicator of fetal health.

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.

Long-term outcomes in multiple gestations

Children born from a multiple gestation are at increased risk for cerebral palsy, learning disability, and language and neurobehavioral deficits. With the increased incidence of multiple pregnancies and use of assisted reproductive technology (ART), these issues are more commonly affecting parents. Long-term outcomes are a critical part of preconceptual and early pregnancy counseling for parents faced with a multiple gestation or considering ART, and the provider should be well versed on issues surrounding zygosity, gestational age, higher-order multiples, and the effects of options such as multifetal pregnancy reduction.

‘Vanishing embryo syndrome’ in IVF/ICSI

BACKGROUND

In a Danish population-based cohort study assessing the risk of cerebral palsy in children born after IVF, we made some interesting observations regarding 'vanishing co-embryos'.

METHODS AND RESULTS

All live-born children born in Denmark from 1 January 1995 to 31 December 2000 were included in this analysis. The children conceived by IVF/ICSI (9444) were identified through the IVF Register, the children conceived without IVF/ICSI (395 025) were identified through The Danish Medical Birth Register. Main outcome measure was the incidence of cerebral palsy. Within the IVF/ICSI children we found indications of an increased risk of cerebral palsy in those children resulting from pregnancies, where the number of embryos transferred was higher than the number of children born.

CONCLUSIONS

The association between vanishing embryo syndrome and incidence of cerebral palsy following IVF requires further investigation in larger, adequately powered, studies.

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.

Multiple Pregnancy: Knowledge and Practice Patterns of Obstetricians and Gynecologists

OBJECTIVE

We sought to assess knowledge and practices of obstetricians regarding multiple gestation.

METHODS

A questionnaire investigating knowledge and practice patterns pertaining to multiple gestation was mailed to randomly selected American College of Obstetricians and Gynecologists (ACOG) Fellows and Junior Fellows in January 2003. Fifty-one percent (589/1,146) of the surveys were returned.

RESULTS

Statistical analysis included the responses from 430 practicing obstetricians. More than 60% rated their training regarding management of multiples as adequate. Men (56.5%) were older and had been in practice longer than females. Sixty-two percent of general obstetrician-gynecologists managed twins without input from a maternal-fetal medicine specialist. An understanding of chorionicity was less than anticipated. The majority of practitioners managed twins according to recent ACOG educational materials. They did not use prophylactic cerclage, home uterine-activity monitoring, or tocolytics. Fort-six percent encouraged prophylactic bed rest. The management of breech second twins varied.

CONCLUSION

Most obstetricians manage multiples according to current ACOG educational materials independent of maternal-fetal medicine specialists. This survey identified knowledge gaps, specifically in chorionicity, indicating the need to develop educational strategies addressing these insufficiencies.

Management of single fetal demise in a multiple gestation

Intrauterine fetal demise of 1 twin in a multiple gestation is a complex clinical situation. Chorionicity, gestational age at diagnosis, problems specific to the pregnancy, and the emotional needs of the patient can impact management. Strategies to optimize outcomes may include a multidisciplinary team approach and fetal surveillance. The following article reviews (1) adverse fetal and neonatal outcomes associated with intrauterine fetal demise of 1 twin, (2) the potential maternal impact, and (3) the strategies to possibly prevent poor outcomes. It is important to remember that even the most vigilant care may not avoid adverse sequelae in a portion of at-risk pregnancies.

Natural history of twin disruption sequence

Intrauterine death of one fetus in a monochorionic twin pregnancy is associated with high morbidity and mortality in the surviving co-twin. Thromoboplastic material from the dead twin may pass to the circulation of the living twin via placental anastomoses and cause tissue necrosis by direct embolization or by activating intravascular coagulation. Alternatively, acute blood loss into the dying twin through placental anastomoses may result in hypotension and hypoxic-ischemic damage to cerebral and visceral tissue in the surviving twin. The resulting clinical picture is referred to as twin disruption sequence. Affected twins have rarely been followed beyond the neonatal period and the long-term development of such children is unknown. Here, we present a natural history and neurological assessment of 18 patients with twin disruption sequence, whom we have followed over several months to years.

Cerebral palsy and intrauterine growth in single births: European collaborative study

BACKGROUND

Cerebral palsy seems to be more common in term babies whose birthweight is low for their gestational age at delivery, but past analyses have been hampered by small datasets and Z-score calculation methods.

METHODS

We compared data from ten European registers for 4503 singleton children with cerebral palsy born between 1976 and 1990 with the number of births in each study population. Weight and gestation of these children were compared with reference standards for the normal spread of gestation and weight-for-gestational age at birth.

FINDINGS

Babies of 32-42 weeks' gestation with a birthweight for gestational age below the 10th percentile (using fetal growth standards) were 4-6 times more likely to have cerebral palsy than were children in a reference band between the 25th and 75th percentiles. In children with a weight above the 97th percentile, the increased risk was smaller (from 1.6 to 3.1), but still significant. Those with a birthweight about 1 SD above average always had the lowest risk of cerebral palsy. A similar pattern was seen in those with unilateral or bilateral spasticity, as in those with a dyskinetic or ataxic disability. In babies of less than 32 weeks' gestation, the relation between weight and risk was less clear.

INTERPRETATION

The risk of cerebral palsy, like the risk of perinatal death, is lowest in babies who are of above average weight-for-gestation at birth, but risk rises when weight is well above normal as well as when it is well below normal. Whether deviant growth is the cause or a consequence of the disability remains to be determined.

The epidemiology and causes of cerebral palsy

Cerebral palsy is the commonest physical disability in childhood, occurring in 2.0 to 2.5 per 1000 live births. Although the total number of children with cerebral palsy has remained stable or increased slightly since 1970, there has been a consistent rise in the proportion of cerebral palsy associated with preterm and very preterm births. Known causes of cerebral palsy--whether prenatal, perinatal or postnatal--must be distinguished from risk factors or associations. Much is known about such risk factors which, alone or in combination, may indirectly result in cerebral palsy. Causes and risk factors implicated in cerebral palsy are discussed in detail, together with directions for future research.

Temporal and demographic trends in cerebral palsy--fact and fiction

The rate of cerebral palsy has not decreased in developed countries over the past 30 years, despite the widespread use of electronic fetal heart rate monitoring and a 5-fold increase in the cesarean delivery rate over the same period of time. However, neonatal survival has improved during these decades. These observations have lead to the hypothesis that increased survival of premature, neurologically impaired infants may have masked an actual reduction in cerebral palsy among term infants as a result of the use of electronic monitoring and the avoidance of intrapartum asphyxia. A review of the medical literature, as well as a demographic analysis of term and preterm birth rates in the United States, refutes this hypothesis on four grounds. First, cerebral palsy prevalence has been separately analyzed in term infants and shows no change over 30 years. Second, the prevalence of cerebral palsy is the same or lower in underdeveloped countries than in developed nations; in the former, the availability of emergency cesarean delivery based on electronic monitor data is limited or absent. Third, the increase in prevalence of cerebral palsy among low-birth-weight infants and the increase in cesarean sections based on presumed fetal distress were not simultaneous events-the former preceded the latter by a decade. Improved neonatal survival since the 1980s has been associated with a stable or decreasing rate of neurologic impairment and thus could not have obscured improvement from reduced term asphyxia. Finally, compared with the number of infants born by cesarean section for fetal distress, there are simply not enough infants born in the most vulnerable weight groups to make any impact on even a minimal improvement of outcome in the group delivered by cesarean section for presumed fetal distress. Except in rare instances, cerebral palsy is a developmental event that is unpreventable given our current state of technology.

The risk of mortality or cerebral palsy in twins: a collaborative population-based study

The purpose of the paper was to describe demographic and clinical factors associated with fetal or neonatal death or cerebral palsy (CP) in twins. Vital statistics from five populations in the United States and Australia, which included information on CP diagnosed after 1 y of age. Information on zygosity was not available. In 1,141,351 births, 25,772 of whom were twins, significant secular trends from 1980 to 1989 included increasing prevalence of twins, increasing proportion of unlike-sex twins, and increasing maternal age. Overall, twins were at an approximately 5-fold increased risk of fetal death, 7-fold increased risk of neonatal death, and 4-fold increased risk of CP compared with singletons. However, at birth weight <2500 g, twins generally did better than singletons, both with respect to mortality and to CP rates. Second-born twins and twins from same-sex pairs were at increased risk of early death but not of CP. Twins from growth-discordant pairs and twins whose co-twin died were at increased risk of both mortality and CP. The highest rates of CP were in surviving twins whose co-twin was still-born (4.7%), died shortly after birth (6.3%) or had CP (11.8%). In this large data set spanning a 10-y period, overall rates of death or cerebral palsy were higher in twins than singletons, although small twins generally did better than small singletons. Co-twin death was a strong predictor of CP in surviving twins. This risk was the same for same- and different-sex pairs, and observed both for preterm and term infants.

Neurological outcome in twins

Twins are at greater risk of death and severe morbidity than singletons which is in excess of that attributable to their greater prematurity. Monozygous, specifically monochorionic, twins are at greater risk than dichorionic twins. The major morbidity is neurological impairment usually presenting as cerebral palsy or severe learning disability and frequently, but not always, associated with fetal death of a co-twin. The likely pathogenesis of the neurological impairment is ischaemia attributable to haemodynamic imbalance via placental vascular anastomoses. In addition to the neurological impairment, congenital cardiac, renal, intestinal and other anomalies are more common but discordant in monozygous twins. It has been hypothesized that cerebral palsy and other neurological impairment in apparently singleton infants is attributable to early loss of a twin, the 'vanishing' twin phenomenon. It is also postulated that other congenital anomalies in singletons may be attributable to the same phenomenon.

Iatrogenic multiple pregnancy

Iatrogenic - physician-made - multiple pregnancies (IMPs) significantly contribute to the epidemic of twins and high-order multiples in most developed and in many developing countries. The primary etiology for IMPs is treatment of reduced fecundity, some but not all of which is associated with specific lifestyle changes of women in the second half of the 20th century. IMPs contribute to increased perinatal morbidity and mortality related to prematurity and low birth weights. In addition, the use of assisted conception techniques increases the frequency of monozygotic twinning and related pathology. Because assisted conceptions are costly interventions, current numbers of IMPs represent a balance between the need to maximize success rates and the desire to minimize the untoward outcome rates. We believe that eliminating procedures associated with unavoidable IMPs and controlling the number of transferred embryos can achieve a significant reduction in the adverse perinatal outcomes and costs associated with IMPs.

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

AIM

To determine the neurodevelopmental morbidity in the surviving twin after fetal or infant death of the co-twin.

METHODS

Twin pregnancies with an antepartum or infant death delivered between 1981 and 1992 were identified from the Northern Perinatal Mortality Survey. Information on the neurodevelopmental morbidity of infant survivors of a deceased co-twin was obtained by a questionnaire sent to the community paediatrician or general practitioner.

RESULTS

A total of 111 children who survived infancy after the fetal death of the co-twin (group 1) and 142 from liveborn twin pairs in which one twin died in infancy (group 2) were traced. Responses were received from 97 (87%) and 130 (92%) respectively. In group 1, the cerebral palsy prevalence was 93 (95% confidence interval (CI) 43 to 169) per 1000 infant survivors; it was more common in like-sex pairs (8/70) with a prevalence of 114 (95% CI 51 to 213) compared with 45 (95% CI 1 to 228) per 1000 infant survivors in unlike-sex pairs (1/22). The overall prevalence of neurodevelopmental morbidity (including developmental delay) was 175 (95% CI 106 to 266) per 1000. In group 2, the cerebral palsy prevalence was 154 (95% CI 84 to 223) per 1000 infant survivors in like-sex (16/104) and 77 (95% CI 9 to 251) in unlike-sex (2/26) survivors; the overall prevalence of neurodevelopmental morbidity was 246 (95% CI 172 to 320) per 1000.

CONCLUSIONS

The risk of cerebral palsy is increased in the surviving twin after a fetal or infant co-twin death compared with the general twin population. Like-sex twins are at greater risk than unlike-sex. The probable cause, in addition to the consequences of prematurity, is twin-twin transfusion problems associated with monochorionicity.

Twins and cerebral palsy

In a national follow-up study of twin births, monozygous compared with dizygous twins were at significantly increased for both to die in utero, one to die in utero and the co-twin to die in infancy, or both to be livebirths but both die in infancy. The prevalence of cerebral palsy among survivors of a co-twin fetal death was 80.2 and other cerebral impairment was 107.0 per 1000. Many apparently singleton cases of cerebral palsy and impairment may be due to fetal death of a twin that has not been recognized or has been recognized but not registered.

Antecedents of cerebral palsy in very low-birth weight infants

Research from the last two decades provides directions for efforts to prevent CP in VLBW infants. The pathogenesis of CP seems to involve factors operating both during pregnancy and in the neonatal period. The most important prenatal factor appears to be intrauterine infection. Perinatal infection and other risk factors, such as the death of a co-twin, placental abruption, and cerebral ischemia, could trigger a cytokine cascade resulting in damage to the developing brain. The low frequency of intrauterine infection in mothers with preeclampsia might explain the apparent protective effect of this disorder. If the brain damage attributed to intrauterine infection and other risk factors involves cytokines as intermediates, then blockade of the proinflammatory cascade or promotion of endogenous inhibitors might prevent CP. Other potentially preventive strategies include corticosteroids given to mothers (but not those given to neonates) and thyroid hormone.

Consequences of in-utero death in a twin pregnancy

BACKGROUND

Twins have a higher mortality and morbidity than singletons and, among twins, the surviving co-twin of a fetus that dies in utero is particularly at risk. We did a cohort study to quantify mortality and serious morbidity in co-twin survivors of fetuses that died in utero.

METHODS

We collected data of all registered twin births in England and Wales between 1993 and 1995 in which one twin was registered as having died in utero. Copies of all death certificates of these fetuses and death certificates of live-born co-twins of fetuses that died in utero were obtained from the Office for National Statistics. A questionnaire was sent to the general practitioners of all surviving co-twins to find out if the child had any disability.

FINDINGS

There were 434 fetal death/live-birth same-sex twin pairs. Among the live births, there were 59 neonatal deaths, seven postneonatal deaths (first 28 days), and five infant deaths (<1 year). In three of the five deaths, the cause of death was cerebral palsy. Ten of the children who survived infancy were lost to follow up. Responses were received from general practitioners for 241 of 353 survivors (68% response). Of the 241 respondents, 23 had cerebral palsy and 28 had other cerebral impairment. Among the children who survived to infancy, the prevalence of cerebral palsy was 106 (95% CI 70-150) per 1000 and prevalence of other cerebral impairment was 114 (80-160) per 1000. There were 163 fetal death/live-birth different-sex twin pairs. Of the live births, 13 died in the neonatal period and four were lost to follow up. Of the 146 survivors, responses were received from the general practitioners for 102 (70% response). Three of the 102 had cerebral palsy and 12 had other cerebral impairment. The prevalence of cerebral palsy was 29 (95% CI 6-83) per 1000 and of other cerebral impairment 118 (62-196) per 1000 infant survivors.

INTERPRETATION

The live-birth co-twin of a fetus that died in utero is at increased risk of cerebral impairment, the overall risk is 20% (95% CI 16-25). The gestational-age-specific prevalence of cerebral palsy after fetal death of the co-twin is much higher than that reported for the general twin population.

Fetal and infant death in mono- and dizygotic twins in England and Wales 1982-91

AIM

To quantify the level of risk for stillbirth and infant death in singleton compared with twin pregnancies, using national data; to determine the independent effects of zygosity, sex, and birthweight on these risks in twin pregnancies.

METHODS

A retrospective national study was carried out of all singleton and twin birth and death registrations in England and Wales 1982-91, according to sex and birthweight group. Weinberg's rule was applied to the twin pairs to differentiate mono- from dizygotic twins. Relative risks for mono- compared with dizygous twins for both twins being stillbirths and for one of the pair being a stillbirth were determined. For twins where one was stillborn and the other live born, the relative risk of neonatal and infant mortality in the surviving co-twin was determined.

RESULTS

There were 6 563 834 registered singletons and 70772 registered twin pairs for the period under study. Monozygotic twins had a relative risk of: 18.91 (95% CI 12.48-28.64) for both twins being stillborn; 1.63 (95% CI 1.48-1.79) for one twin being a stillbirth; and 2.26 (95% CI 1.45-3.52) for the live born co-twin dying as a neonate. When both twins were live born and among singletons, the odds ratio for neonatal mortality of being male was 1.41 (95% CI 1.37-1.45) and there was a highly significant negative association with birthweight. After adjusting for birthweight group and sex, twins had a reduced neonatal mortality compared with singletons: odds ratio 0.91 (95% CI 0.85-0.96).

CONCLUSIONS

Fetal death in one of monozygotic twins has serious implications for survival of the co-twin. Monochorionicity is probably the essential feature of the increased risk to the co-twin. It is imperative that all fetal deaths in multiple pregnancies are recorded and chorionicity determined if parents are to be adequately counselled.

The neurologically impaired child and alleged malpractice at birth

Controlled studies, improved epidemiologic and statistical techniques, and an increase in biological information on mechanisms of fetal and neonatal brain injury or maldevelopment have led to a better, although still imperfect, understanding of the cause of developmental disabilities. The role of asphyxia during the birth process is smaller than was once believed. Intrauterine exposure to infection, autoimmune and coagulation disorders, and problems specific to multiple pregnancies are risk factors for cerebral palsy. Electronic fetal monitoring and other observations during birth are unsatisfactory management guides, having enormously high rates of false-positive identification. There is no evidence that caesarean section can prevent cerebral palsy in term infants.

[Periventricular leukomalacia. I. Histological and pathophysiological aspects]

The term 'periventricular leukomalacia' (PVL) usually covers necrotic and/or gliotic lesions from perinatal origin occurring in the periventricular ring of telencephalic white matter. PVLs are found post-mortem in one third of brains from autopsies of premature infants; PVLs are diagnosed in 4 to 10% of infants born before 33 weeks of gestation and remaining alive more than 3 days after birth. PVL is very rare in at term infants. The proportion of PVLs from prenatal origin is estimated between one third and one half of cases. Recent progresses in neuroepidemiology, developmental neurobiology and imaging methods permit to revisit the pathophysiology of PVLs on a multifactorial basis. The final result of these multiple factors seem to be calcium influx due to glutamatergic overactivation triggered by cytokines, infection and inflammation, and deficit in neurotrophic factors. Periventricular topography can be explained by properties of intracerebral vascular wall at this stage of angiogenesis and by perfusion failure/hypoxia.

Adverse outcome after multiple pregnancy

There is increasing interest in the outcomes of multiple pregnancies as their numbers rise, mainly owing to advances in fertility-enhancing techniques. In addition, the numbers of multiple births surviving the perinatal period is increasing with the increasing survival of very tiny babies. In order to investigate these outcomes or to evaluate procedures that may improve them, it is important to consider a number of methodological issues that affect the comparability of data both between and within populations. How a birth and a multiple birth are defined, data sources, whether multiple pregnancies or individual births are being counted and the identification of multiple gestations by zygosity and chorionicity will all affect the reported outcome rates. In light of this, perinatal mortality and neurodevelopmental disabilities are examined as adverse outcomes of multiple pregnancies.