Neurologic Outcome in the Surviving Twin
ABSTRACT & COMMENTARY
Synopsis: Studies using registries of this type are open to criti- cism. For example, while different-sexed twins are dizygotic, not all same-sexed twins are monozygotic. Nevertheless, this information will be important in counseling patients when one twin has died in utero, an event that complicated 2.4% of the more than 25,500 twin pregnancies in this registry.
Source: Pharoah POD, Adi Y. Lancet 2000;355:1597-1602.
To determine the prevalence of cerebral palsy in the surviving co-twin of a fetus that had died in utero, these investigators performed a cohort study of all registered twin births in England and Wales between 1993 and 1995. A questionnaire was sent to the general practitioners of all surviving co-twins to determine if that child had a neurologic disability. Pharoah and Adi contrasted outcome in same-sex twins vs. different-sex twins to reflect the risks associated with monozygotic vs. dizogotic twins. Follow-up information was obtained for 241/353 surviving same-sexed twins (68%) and 102/146 surviving different-sexed twins (70%). Among same-sexed twins, the prevalence of cerebral palsy was 106/1000 and for cerebral impairment 114/1000. Cerebral impairment included language, hearing, and motor problems. The prevalence of cerebral palsy was significantly lower in different-sexed surviving twins, 29/1000 but the rate of impairment was not different, 118/1000.
Overall, the prevalence of cerebral palsy in the live-born co-twin of a fetus that has died in utero was 83/1000 infant survivors, a 40- fold increase over the background population prevalence for cere- bral palsy. Furthermore, the risk of serious neurologic morbidity was 20% for the surviving co-twin.
Comment by Steven G. Gabbe, MD
Twin gestations are well known to be associated with increased perinatal morbidity and mortality and, among twin gestations, monozygotic twins are at the highest risk. This cohort study by Pharoah and Adi reports a marked increase in both cerebral palsy and cerebral impairment in the surviving co-twin after the death of one twin in utero. The mechanism responsible for the increased neurologic morbidity is not clear. It has been suggested that emboli from the dead twin may cause cerebral infarction in the surviving twin or that hypotension in the surviving twin causes cerebral ischemia. If these mechanisms are responsible, as Pharoah and Adi point out, early intervention after the death of one twin is unlikely to prevent neurologic injury in the surviving co-twin.
Studies using registries of this type are open to criticism. For example, while different-sexed twins are dizygotic, not all same-sexed twins are monozygotic. Nevertheless, this information will be important in counseling patients when one twin has died in utero, an event that complicated 2.4% of the more than 25,500 twin pregnancies in this registry.
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