Cerebellar growth in normal and growth-restricted fetuses of multiple gestations

OBJECTIVE: Our purpose was to evaluate growth of the cerebellum in growth-restricted fetuses of twin and triplet gestations versus growth in normal in utero sibling(s) and in singleton gestations. STUDY DESIGN: An ultrasonographic study was conducted in a population of pregnant women with twin and triplet gestations. The control group was either the normal in utero sibling(s) when one fetus was growth restricted or normal twin and singleton pregnancies. Standard biometric measurements were obtained on all fetuses throughout pregnancy, including the transverse cerebellar diameter. However, only the last measurement was used for the analysis. Statistical analyses were conducted comparing growth of the transverse cerebellar diameter among the growth-restricted fetuses versus growth in the normal in utero fetal sibling(s) or other normal twin and singleton gestations. RESULTS: Pregnancies were categorized on the basis of the growth status of women with twin and triplet gestations: Group 1 (151) contained women with two fetuses appropriately grown for gestational age; group 2 (52) had one appropriately grown fetus and one with intrauterine growth restriction; group 3 (19) had two fetuses with intrauterine growth restriction. In addition, there were 30 triplet gestations (group 4), five of which had growth-restricted fetuses, and group 5 contained 1405 singleton pregnancies. In all five groups there was a statistically significant relationship between transverse cerebellar diameter and gestational age (p < 0.0001). There was also no significant difference between growth of the transverse cerebellar diameter in the appropriately grown and growth-restricted siblings and among normal singleton and twin pregnancy groups. In most cases of growth-restricted fetuses, except for the transverse cerebellar diameter measurements, all other biometric parameters were < 10th percentile. CONCLUSION: These data confirm the relative preservation of normal cerebellar growth in growth-restricted fetuses and a similar rate of growth in singleton and multifetal gestations. The transverse cerebellar diameter therefore represents an independent biometric parameter that can be used in both singleton and multifetal pregnancies to assess normal and deviant fetal growth.