Hematological parameters immediately after birth in twins and higher order multiples

To develop reference values for hematological parameters in twins and higher order multiple births immediately after birth and compare them with values from singletons.

In this retrospective matched cohort study, hematological parameters immediately after birth from multiples, and gestation- and sex-matched singletons born between 2007 and 2009 were obtained. Infants born with maternal or fetal conditions known to affect hematological values were excluded. Data were compared using Student t-test, chi-square test, and nonparametric tests as appropriate.

Three hundred sixty-three multiples were matched with 363 singletons. Multiples had lower birth weights and higher rate of conception by in-vitro fertilization than singletons. Mean (SD) hemoglobin (171 ± 24 vs. 167 ± 23 g/L; p = 0.04) was marginally higher but nucleated red cells were 30% lower (1.7 ± 2.6 vs. 2.6 ± 3.9 10(9)/L, p < 0.01) in multiples. Total white blood cells (WBCs) were 14% lower, absolute neutrophils 30% lower, monocytes 31% lower, basophils 28% lower, and immature WBC 56% lower in multiples.

Mean hemoglobin was higher, whereas total WBC, absolute neutrophils, monocytes, and eosinophils were significantly lower in multiples compared with singletons. These differences in WBC and neutrophil counts should be considered when interpreting hematological parameters in multiples.