Birth order modifies the effect of IL13 gene polymorphisms on serum IgE at age 10 and skin prick test at ages 4, 10 and 18: a prospective birth cohort study

Table 2 Comparison between children with and without total serum IgE measurements at age 10

	IgE at age 10 (n (%))	No IgE at age 10 (n (%))	Exact
Study Variables	N = 953	N = 583	p-values
Birth order
- First	354 (41.0)	156 (44.7)	0.50
- Second	303 (35.1)	116 (33.2)
- Third or higher	206 (23.9)	77 (22.1)
Family Social Status Cluster*
- High	80 (8.5)	31 (7.5)	0.02
- Middle	737 (78.0)	300 (72.8)
- Low	128 (13.5)	81 (19.7)
Environmental Tobacco Exposure**
- ETS-0	451 (47.5)	196 (36.0)	<0.0001
- ETS-1	300 (31.6)	164 (30.1)
- ETS-2	199 (21.0)	185 (33.9)
Gender
- Male	479 (50.3)	306 (52.7)	0.37
- Female	474 (49.7)	275 (47.3)
Prematurity (weeks)
- < 37	26 (2.8)	23 (4.1)	0.23
- ≥ 37	904 (97.2)	544 (95.9)
Low Birth Weight (g)
- < 2500	33 (3.6)	28 (4.9)	0.23
- ≥ 2500	894 (96.4)	539 (95.1)

*"Family social status cluster" is a composite variable derived from a combination of family income, parental occupation (socioeconomic status), and number of children in child's bedroom.
** ETS-0: mother did not smoke during pregnancy and children not exposed to household environmental tobacco smoke (ETS);
ETS-1: mother did not smoke during pregnancy, but children were exposed to household ETS;
ETS-2: mother smoked during pregnancy and children were exposed to household ETS.

ISSN: 1710-1492