Is less intensive fetal surveillance of dichorionic twin gestations justified?

Twin gestations exhibit significantly increased perinatal morbidity and mortality rates in comparison with singleton gestations. The perinatal mortality in twins is 3±7 times higher than in singletons. While accounting for only 2.5% of the population, twins account for 12.6% of the perinatal mortality. A marked recent increase in the incidence of twinning (and other high-order multiple gestations) has occurred, reflecting widespread assisted reproductive technology (ART) modalities. As a result, approximately 50% of twin gestations currently result from infertility treatment. In addition this recent increase in the incidence of twin gestations occurs in a `skewed' fashion, with increased representation of older patients, possibly already at risk for increased uteroplacental perfusion-related, and other maternal age-related complications of pregnancy, for example, abnormal placentation. Various modalities of fetal surveillance of twins include: daily fetal kick counts, non-stress fetal testing, fetal biophysical profiles, Doppler velocimetry, ultrasonographic assessment of interval fetal growth, and enhanced surveillance of discordant twins and affected twins in twin±twin transfusion syndrome. Overall, these wide-ranging methods of increased surveillance of twins have not been investigated in a prospective fashion (randomized and stratified according to chorionicity). Accordingly, established guidelines as to the nature of testing and more specifically, currently recommended intervals between testing, are neither evidence-based or uniformly practiced. Nevertheless, most patients with antenatally detected twin gestations, are followed with increased fetal surveillance intensity in comparison with women with singleton fetuses.