ABSTRACT
Twin gestations are at significant increased risk for adverse perinatal outcome. As
a result, although prospective randomized data is lacking, increased fetal surveillance
has been advocated for twins. Growth concordance is considered a reassuring sign in
twins and conversely, discordancy to possibly reflect a hostile intrauterine environment
at least to the smaller twin. Consequently, increased surveillance of discordant twins
is commonly practiced. Monochorionic twins are at further risk for type-specific perinatal complications, for example, twin-twin transfusion syndrome. Recently, precise
first-trimester depiction of chorionicity has enabled early antepartum stratification
of twin gestations according to chorionicity, in comparison with previous later (mid-
and third-trimester) ultrasonographic diagnosis of chorionicity. This immediately
leads to the question whether antenatal testing of twins should differ according to
chorionicity? Review of the literature supports that despite the existence of complications
unique to monochorionic twin gestations, dichorionic twins sustain an increased risk
of adverse perinatal outcome (such as fetal growth restriction) in comparison with
singletons, and that close antenatal fetal surveillance of twins should be performed,
irrespective of chorionicity.
KEYWORD
Twin gestations - antenatal testing - perinatal outcome - chorionicity
