Sequential C3 and C4 levels in human milk in relation to prematurity and parity

Similarly to many immune molecules of human milk, C3 and C4 levels decrease during lactation. We investigated the influence, over the first three week s of lactation, of both prematurity and parity on the sequential evolution of these levels. Milk C3 and C4 concentrations were measured by immunonephe lometry in 494 individual samples collected from 76 lactating mothers. C3 a nd C4 concentrations were higher in milk from preterm or primiparous mother s. The major differences were observed in milk from days 5-8 and 9-20, like ly due to pronounced interindividual variations in levels of days 1-4 milk. Milk from mothers of precocious (33 weeks' gestation or less) preterm newb orns presented higher concentrations and a slower decrease dr C3 and C4 lev ers than that from mothers of late (33-37 weeks' gestation) preterm newborn s, when compared to term mothers. Finally, the inversion of the C3/C4 ratio occuring over time, previously reported, appeared later in milk from mothe rs of preterm newborns. The influence of prematurity was even greater in pr imiparous than in multiparous mothers. Both C3 and C4 levels therefore appe ar to be influenced in human milk by the parity and prematurity of the deli very. Mothers from preterm newborns seem to provide higher levels of C3 for a longer period post delivery.