Is thrombopenia in cord blood indicative of intra‐uterine sensitization?

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Abstract
The relation between platelet counts (PCT) and IgE was studied in cord blood from 136 European newborns. PCT was significantly lower (P = 0.0014) when cord-IgE was superior to 1.20 IU/ml (n = 29; 245,000/.mu.l) than when it was inferior to this value (n = 107; 284,080/.mu.l) which resulted in a significant negative Spearman rank correlation between PCT and cord-IgE (P = 0.002; rs = -0.25). A follow-up by questionnaire in 97 of the newborns revealed that those newborns who had developed definite atopy within 18 months of age had significantly (P = 0.002) lower PCT at birth (n = 8; 196,000/.mu.l) than those free of atopic symptoms (n = 61; 286,000/.mu.l). Further newborns to atopic mothers (n = 23; 245,000/.mu.l) had significantly (P = 0.0014) lower PCT than newborns to non-atopic mothers (n = 74; 286,000/.mu.l). The lowest PCT was recorded when both the mother was atopic and the newborn had developed definite or probable atopy by the age of 18 months (n = 7; 175,000/.mu.l) as compared to atopy alone in mothers (n = 16; 276,000/.mu.l; P = 0.005), to atopy alone in infants (n = 9; 281,000/.mu.l; P = 0.005) and to non-atopic infants of non-atopic mothers (n = 65; 286,000/.mu.l; P = 0.0007). Significantly (P = 0.03) lower PCT amongst boys (n = 49; 259,000/.mu.l) compared with girls (n = 48; 294,000/.mu.l) was attributed to the higher incidence of elevated cord-IgE and infant atopy among boys. These findings were limited to PCT, since the erythrocyte count, hematocrit and hemoglobin concentration in cord blood did not significantly (P > 0.10) differ in any of these groups. Paternal atopy and atopy in siblings did not influence PCT, neither did maternal smoking or drug intake (progesterone and .beta.-mimetics) during pregnancy. These data as a whole are compatible with a direct or indirect role for platelets and their mediators in immediate hypersensitivity reactions. We speculate that a low PCT in cord blood of newborns reflects an on-going intra-uterine sensitization and therefore it might be a complementary parameter to family history and cord-IgE in predicting newborns at high risk of developing atopy.