Previous reports suggest that when one twin dies in utero, the survivor is more likely to suffer serious adverse outcomes, such as cerebral palsy, gut atresia, and learning disability. An attempt was made to quantify the risk of cerebral impairment in a series of 434 same-sex twin pairs in which one twin died before birth. Cases included all twin births registered in England and Wales between 1993 and 1995. Fifty-nine of the liveborn infants died neonatally, seven others within the first 28 days, and five within 1 year of birth. Three of the latter deaths were a result of cerebral palsy. Ten children who lived through infancy were lost to follow-up. Of 241 infants for whom follow-up information was available, 23 had cerebral palsy and 28 had other forms of cerebral impairment. Of those surviving to infancy, the prevalences of cerebral palsy and cerebral impairment were 106 and 114 per 1000, respectively. Among 163 different-sex twin pairs, 13 survivors died neonatally. Three of 102 survivors had cerebral palsy, and 12 had other forms of cerebral dysfunction for prevalences of 29 and 118 per 1000 infant survivors, respectively. Analysis of the combined data demonstrated a 40-fold higher prevalence of cerebral palsy in these infants than in the general population. Including other cerebral impairment, the overall risk of serious cerebral dysfunction is 20 percent.
It is likely that most cases of cerebral impairment in the infants of this series were the product of monochorionic twin pregnancies. If this is the case, the risk of serious cerebral morbidity in survivors of such pregnancies will exceed one in five. The risk could approach 40 percent to 50 percent, assuming that all cases in same-sex twins involved monochorionic twins. The chances of in utero death and of a liveborn infant dying during infancy are considerably increased in monozygous as compared with dizygous twins. Reason may include disseminated intravascular coagulation resulting from the release of thromboplastic material and infarction from emboli originating in the dead twin. Unstable blood pressure and severe hypotension also have been implicated. If these factors are in fact responsible, early obstetrical intervention after the in utero death of one twin probably will not prevent morbidity in the surviving twin. These findings emphasize the need to accurately record placentation.