(ChemotherapyAdvisor) – Epidemiological associations between birth weight, birth order, and other perinatal factors with childhood leukemia vary by leukemia subtype, according to a study of California Cancer Registry data published in Cancer Epidemiology.

Among 5,788 children with leukemia and 5,799 age- and sex-matched controls, high birth weight and large-for-gestational-age birth were associated with an increased risk of total childhood leukemia (acute myeloid leukemia [AML] and acute lymphoblastic leukemia [ALL]) and ALL, while small-for-gestational-age birth was associated with a decreased risk for total leukemia and ALL.

“For AML, increased risk was found for heaviest babies but estimates were imprecise,” reported senior author Leeka I. Kheifets, professor in residence of public health and epidemiology at UCLA in Los Angeles, California, and coauthors.

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Odds ratios (ORs) per 1,000g increase in birth weight was 1.11 for total leukemia and ALL risk, with the highest ORs for babies weighing ≥4500g at birth (OR=1.59; 95% CI, 1.05-2.40 for total leukemia; OR-1.7; CI, 1.08-2.68 for ALL), the authors reported. First-born babies faced a significantly decreased risk of AML (OR=0.70, 95% CI, 0.53,0.93), but not total leukemia or ALL.

Maternal age, previous pregnancy complications, and terminated pregnancies were not associated with leukemia risk, but older fathers were associated with increased risks of ALL and total leukemia (fathers between the ages of 35 and 45 years at child’s birth vs. <25 years: OR=1.23; CI, 1.04-1.47).

Birth weight may be associated with childhood leukemia because of elevated levels of insulin-like growth factor 1 (IGF-1) or because of the larger volume of bone marrow (and therefore, larger number of bone marrow cells and a resulting higher probability of malignant transformation) in larger babies, the authors wrote.

“These findings suggest that associations of childhood leukemia and perinatal factors depend highly on subtype of leukemia, which needs further evaluation,” the authors concluded.

The authors reported no conflicts of interest. The study was funded in part by the Electric Power Research Institute (EPRI).