If One Twin Dies In Utero, The Other Is at Risk of Cerebral Impairment

OB/GYN News, Sept 1, 2000 by Mary Ann Moon

When one twin fetus dies in utero, at least one in five surviving twins is at risk of serious cerebral impairment, according to Dr. P. O. D. Pharoah and Dr. Y Adi of the University of Liverpool (England).

Investigators surveyed the physicians of 348 children whose co-twins had died in utero. Participants were identified from a database of all twin births in England and Wales between 1993 and 1995. They were asked whether the surviving twins had any physical disabilities, cerebral palsy, congenital abnormalities, or delay in achieving developmental milestones.

Findings from case studies, as well as population-based surveys of patients with cerebral palsy had previously suggested that surviving twins were at increased risk of cerebral impairment. The investigators attempted to quantify that risk.

In their investigation, Drs. Pharoah and Adi found that 29 surviving twins were found to have cerebral palsy-for a prevalence of 83/1,000 live births --representing as much as a 40-fold increase in cerebral palsy prevalence, compared with the general population, the investigators said (Lancet 355[9215]:1597-1602, 2000).

Other forms of cerebral impairment, including developmental delays, late language development, visual or hearing impairment, and significant behavioral problems, affected 40 children. The prevalence of these impairments was 115/1,000 live births.

The overall risk of serious cerebral impairment was 20% in the surviving twin whose co-twin died in utero.

The risk could be "considerably higher," as much as 40%-50%, in surviving twins of monochorionic pregnancies. However, in such cases the risks could not be quantified because the database did not differentiate between monozygous and dizygous twin pairs.

Since the children were aged 3-5 years at the time of the survey, many more may still prove to have learning disabilities that become recognized when they reach elementary school age, the investigators noted.

The pathologic mechanism of cerebral impairment remains unknown.

Research suggests that dissemination of intravascular coagulation may occur "as a result of the release of thromboplastic material or infarction due to emboli from the dead twin." Additionally blood pressure instability or severe hypotension after the death of the co-twin might produce brain lesions in the survivor, Dr. Pharoah and Dr. Adi said.

If such mechanisms are indeed responsible, it is unlikely that even early intervention after the intrauterine death of one twin will prevent sequelae in the surviving twin, they said.

However, the type of circulatory anastomoses between the twins-whether arterioarterial, arteriovenous, or venovenous--also may play a role.

Technologic advances in assessing the degree of circulatory interchange could lead to appropriate preventive strategies," they added.