Table 1 Group characteristics at birth.

	CF (n = 39)	Control (n = 21)	Mean (95% CI) difference*
Boys (%)	12 (31)	9 (43)	–12 (–36 to 12)
Gestational age (weeks)	39 (2.1)	39.7 (1.2)	–0.8 (–1.6 to 0.1)
Birth weight (kg)	3 (0.6)	3.3 (0.4)	–0.3 (–0.6 to 0.02)
Birth weight (Z score)	–0.5 (1.1)	–0.3 (0.8)	–0.2 (–0.8 to 0.3)
Maternal smoking during pregnancy, n (%)	12 (31)	6 (29)	2% (–22 to 24)
Maternal ethnic group, n (%) white	36 (92)	20 (95)	–3% (–16 to 16)
Maternal history of asthma, n (%)	14 (36)	5 (24)	12% (–13 to 33)

CF, cystic fibrosis.

Results expressed as mean (SD) unless otherwise specified.

*Difference calculated as cystic fibrosis−control.