Intrauterine growth retardation of unknown etiology. I. Serum complement and circulating immune complexes in mothers and infants.

Complement (C) and circulating immune complexes (CIC) levels were measured in 22 full-term pregnant women and 15 of their small-for-gestational-age (SGA) offspring in order to seek evidence supporting an immunological etiology for placental lesions related to idiopathic intrauterine growth retardation. We used 19 normal full-term pregnant women and 18 of their infants with birthweight above the 25th centile of the ponderal curve as a control population for this study. C levels were significantly lower in mothers of SGA infants than in controls (146.6 +/- 46.6 and 183.6 +/- 36.6 respectively, p less than 0.01). CIC were present in the sera of 5 out of 22 mothers of the SGA group and in 3 out of the 15 infants sera. No CIC were found in the sera of mothers or infants from the control group. Placental lesions were observed in 14 out of the 22 (64%) cases studied in the SGA group and in 1 of 11 (9%) of the controls. Two placentas from SGA infants showed acute atherosclerosis, and deposits of IgM and C3 were found in their vessel walls. These data are in favor of an immunological mechanism for intrauterine growth retardation of unknown etiology.