ABSTRACT: Triplets often have a low birth weight. This is partly due to low gestational age; they are often born premature. However, zygosity and chorionicity also affect birth weight. Triplets, which refers to one child (the set of three triplets is referred to as a 'trio'), can be either monochorionic (MC), dichorionic (DC) or trichorionic (TC). A smaller number of chorions is associated with lower birth weight because sharing a placenta causes competition for nutrients (Adegbite, Ward, & Bajoria, 2005; Bajoria, Ward, & Adegbite, 2006; Geipel et al., 2005). In addition, there is some evidence that when more triplets share a chorion the gestational age of the trio is lower (Spencer et al., 2009). Zygosity also is an important factor in birth weight, but is not independent from chorionicity. Monozygotic (MZ) triplets can share one chorion, can be DC, or have each their own chorion (i.e. trichorionic, TC); dizygotic (DZ) triplets are DC or TC; trizygotic (TZ) triplets are always RECEIVED 24 December, 2011; ACCEPTED 10 January, 2012.
Twin Research and Human Genetics 01/2012; 15(10-2):149--157. · 1.70 Impact Factor