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

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.

Discordance of prenatal and neonatal brain development in twins

BACKGROUND

Discordance of birth weight has been observed in twin pairs, though little is known about prenatal and early neonatal discordance of head and brain size, and the role that zygosity and chorionicity play in discordances of early brain development in twins.

AIMS

To compare prenatal and neonatal discordances of head size in monozygotic-monochorionic (MZ-MC), monozygotic-dichorionic (MZ-DC), and same-sex dizygotic-dichorionic twin pairs (DZ).

STUDY DESIGN

Subjects prospectively had ultrasounds at 22 and 32 weeks gestational age, and magnetic resonance imaging (MRI) of the brain MRI after birth.

SUBJECTS

88 twin pairs recruited from two university hospital prenatal diagnostic clinics; 22 MZ-MC, 17 MZ-DC, and 49 same-sex DZ pairs.

OUTCOME MEASURES

Discordance of head circumference (HC) and weight at 22 weeks, 32 weeks and birth, as well as intracranial volume (ICV) on neonatal MRI.

RESULTS

There were no group differences in discordance of head circumference and weight on the 22 or 32 week ultrasounds, or at birth. MZ-MC twins tended to have numerically greater discordances of HC and weight. There was a significant group difference in ICV on neonatal MRI (ANOVA, p=0.0143), with DZ twins having significantly greater discordance than MZ-MC (p=0.028) or MZ-DC (p=0.0131) twins.

CONCLUSIONS

This study indicates that zygosity and chorionicity do not contribute to significant discordances of head size in late prenatal development. DZ twins do have significantly greater discordances of ICV on neonatal MRI, suggesting a relatively greater genetic influence on brain growth in the first weeks after birth.

Selective fetoscopic laser photocoagulation of superficial placental anastomoses for the treatment of severe twin-twin transfusion syndrome

OBJECTIVE

To report our initial institutional experience with fetoscopic laser photocoagulation of placental anastomoses in severe twin-twin transfusion syndrome using a 1.0 mm endoscope.

METHODS

Between July 2006 and June 2008, 19 monochorionic diamniotic twin pregnancies complicated by severe TTTS (Quintero stages III and IV) underwent fetoscopic laser therapy. Perinatal data were prospectively collected and compared according to the Quintero stages.

RESULTS

Nine patients were classified as stage III and ten as stage IV. The Mean gestational ages at diagnosis and procedure were 20 (range: 17-25) and 22.0 (range: 19.0-26.0) weeks, respectively, with no statistical difference between the two groups. Preterm premature rupture of the membranes occurred in two cases (10.5%), and spontaneous preterm delivery in eight (42.1%). Overall mean gestational age at delivery was 32.1 (range: 26.0-38.0) weeks. Prematurity was more severe in stage IV patients (p<0.01). Among all cases, the overall survival rate was 52.6%, and the percentages of pregnancies with survival of both babies and at least one twin were 26.3% and 78.9%, respectively. In the case of stage III patients, the overall survival rate was 61.1%. Of the stage III pregnancies, 33.3% resulted in both babies surviving, and 88.9% of these pregnancies resulted in at least one surviving twin. For stage IV, as the corresponding statistics were 45.0%, 20.0% and 70.0% respectively.

CONCLUSIONS

Our initial institutional experience with 1.0 mm fetoscopic laser therapy for severe TTTS showed results similar to those reported in the literature for larger endoscopes.

The value of umbilical artery Doppler velocimetry in the antenatal surveillance of uncomplicated monochorionic twin pregnancies

OBJECTIVES

To investigate the predictive value of abnormal umbilical artery Doppler findings on outcome in uncomplicated monochorionic (MC) twin pregnancies.

METHODS

Sixty-seven MC twin pregnancies, with antenatal care and delivery at the University Medical Center, Utrecht, The Netherlands, between 1999 and 2004, were studied. Pregnancies with antenatal signs of twin-to-twin transfusion syndrome were excluded. We analyzed the data according to both the last Doppler measurement of the umbilical artery before delivery and the presence of any abnormal Doppler measurement during the course of pregnancy. Risks of mortality and total neonatal morbidity were stratified according to the Doppler findings in one or both fetuses at the time of each standard ultrasound assessment in order to estimate the risk associated with an abnormal Doppler finding at or before that specific gestational age.

RESULTS

Mortality rates were similar in the normal and abnormal Doppler groups. Using both group definitions, total neonatal morbidity was higher in the abnormal Doppler group; this was significant at > 32 weeks' gestation, and was due to lower birth weight and earlier gestational age at delivery. There was no mortality at > or = 36 weeks in the abnormal Doppler group, but there were four perinatal deaths in the normal Doppler group. Gestational age at delivery was significantly lower when one or more abnormal Doppler findings had been present (median, 34 + 1 weeks vs. 36 + 3 weeks) and infants with abnormal Doppler findings weighed on average 261 g (95% CI, 21-502 g) less than those with normal findings.

CONCLUSIONS

In MC twins, abnormal Doppler flow of the umbilical artery identifies a subgroup at risk for preterm delivery, low birth weight and neonatal morbidity, but with a similar mortality risk to those with normal Doppler flow. At term, mortality occurred only in the group with normal Doppler findings, suggesting that fetal surveillance is insufficient in uncomplicated term MC twin pregnancies.

Growth abnormalities and multiple gestations

Growth abnormalities which include intrauterine growth restriction and weight discordance between twins are common in pregnancies complicated by multiple gestations and may be associated with poor perinatal outcomes. Knowledge of chorionicity is paramount when managing a multiple pregnancy. Monochorionic twins are at greater risk than dichorionic twins for growth issues, which may result in long-term complications including adverse neurological sequelae for the offspring. The purpose of the following article is to define normal and abnormal growth in multiples. In addition, the management of growth abnormalities in relationship to chorionicity will be discussed.