The in vitro production of bovine embryos by in vitro fertilization or nuclear transfer procedures is a powerful tool in wide use for scientific, conservationist and commercial purposes. However, developmental abnormalities are unpredictable consequences of such in vitro embryo manipulations, which may interfere with the pattern of fetal and placental growth and life ex utero, in a set of symptoms collectively called Large Offspring syndrome (LOS). The economical significance of the syndrome is associated with increased rates of pregnancy losses, placental and fetal aberrations that culminate in abortion, hydrops of the fetal membranes, prolonged gestation, diminished signs of parturition, dystocia, and birth of large calves with lower postnatal survival. Lower pregnancy rates with higher gestational and postnatal losses represent significant economical losses for a lower prolificacy. The un derstanding of mechanisms of prenatal growth in normal development and in those related to the syndrome will be of significance for prevention or attenuation of abnormalities of common occurrence in cattle, with potential direct scientific and economical implications.