LEP and fetal growth restriction: In addition, it is possible that the dysregulation of leptin gene expression between SGA (IUGR) and AGA co-twins may be associated with the local environment typical for the SGA fetus, as indicated by the lack of any significant differences between the leptin gene expression by AGA of IUGR/AGA vs. both AGA co-twins from AGA/AGA pregnancies, and between SGA + AGA (from IUGR/AGA pregnancies) vs AGA + AGA (from AGA/AGA gestations).