[Related factors in the development of anemia in preterm infants]

To investigate the related perinatal factors in the development of anemia of prematurity by a case-control study.

The medical data of 165 preterm infants admitted to the department of neonatology in Peking University Third Hospital from January 2005 to December 2006 were retrospectively reviewed. The infants were classified into two groups: anemia and non-anemia (control). The factors associated with anemia of prematurity were identified.

Sixty-three preterm infants (38.1%) had anemia. The gestational age (32.5+/-2.0 weeks vs 33.7+/-1.9 weeks) and birth weight (1682.7+/-393.9 g vs 2041.1+/-510.1 g) of the anemia group were significantly lower than those of the control group (P<0.01). The blood loss from laboratory testing (12.4+/-6.5 mL/kg vs 6.6+/-3.6 mL/kg) and the duration of hospital stay (25.6+/-14.2 days vs 14.1+/-8.7 days) of the anemia group were significantly higher than those of the control group (P<0.01). More critically ill patients (33.3%) were noted in the anemia group compared with in the control group (9.8%) (P<0.01). In the anemia group, 44.4% of the mothers had preeclampsia but only 28.4% in the control group (P<0.05). Multiple factor logistic regression analysis revealed that the blood loss from laboratory testing was the only independent high-risk factor for anemia of prematurity. Compared with the preterm infants whose blood loss from laboratory testing was < 5 mL/kg, the OR values of the preterm infants whose blood loss was 5-10, 10-15 and > or = 15 mL/kg was 1.737 (95% CI: 0.699-4.316, P>0.05), 4.141 (95% CI: 1.573-10.905, P<0.01) and 32.267 (95% CI: 8.053-129.287, P<0.01), respectively.

Anemia of prematurity is associated with gestational age, birth weight, duration of hospital stay, illness severity and maternal preeclampsia. The blood loss from laboratory testing is an independent risk-factor in the development of anemia of prematurity.