Fig. 3.
Sulcation index quantification among groups at birth. (A and B) Average of the sulcation index (SI1) according to group (with standard error in plot bars), estimated by a model with age GA1 [(A) mean GA1 = 32.2 weeks] or cortical surface S1 [(B) mean S1 = 247 cm2] as co-variable (Table 2), showing lower index in twins and IUGR newborns compared with singletons of equivalent age (A) but higher index in IUGR newborns compared with singletons and twins with similar surface (B). (C and D) Examples of inner cortical surface, with sulci outlined in colour, for a singleton and a twin of equivalent age [(C) GA1 30.3/30.3 weeks; S1 224/164 cm2; SI1 0.119/0.038], and for a singleton and an IUGR newborn with similar surface [(D) GA1 28.6/32.1 weeks; S1 192/189 cm2; SI1 0.043/0.126].