Table 2.

Characteristics of women giving birth at term and relative risk of stillbirth by time

	2000–2002	2003–2005	2006–2008	2009–2010	2011–2012
Mean age (years)	30.1	30.6	30.8	30.9	30.9
Mother ≥40 years	3584	4366	5436	3740	3777
% ≥40 years	2.0	2.4	3.0	3.2	3.5
BMI recorded (n)	NA	112 635	167 962	111 972	106 201
Mean BMI	NA	24.1	24.2	24.3	24.4
BMI >25	NA	36 076	54 903	37 616	36 528
% BMI >25	NA	32.0	32.7	33.6	34.4
BMI >30	NA	12 480	19 683	13 946	13 720
% BMI >30	NA	11.1	11.7	12.5	12.9
BMI >35	NA	4032	6813	4880	4689
% BMI >35	NA	3.6	4.1	4.4	4.4
Smoker	37 540	30 782	25 656	14 891	12 527
% smokers	20.5	17.1	14.2	12.6	11.5
Multiple pregnancies	4353	4617	4727	3116	2747
% multiples	2.4	2.6	2.6	2.6	2.5
Stillborn multiples	51	111	61	40	29
% stillborn multiples	1.2	2.4	1.3	1.3	1.1
Para 0	78 718	77 231	77 685	51 675	48 584
% Para 0	43.0	42.9	43.0	43.8	44.5
Regression analysis	HR* of stillborn (2000–2002 reference)
Crude	1	0.95	0.89	0.72	0.59
Adjusted for GA	1	1.02	0.98	0.78	0.65
95% CIs		0.89 to 1.17	0.85 to 1.12	0.66 to 0.92	0.53 to 0.78
Adjusted except plurality‡§	1	1.03	0.89	0.73	0.62
95% CIs		0.90 to 1.18	0.78 to 1.03	0.61 to 0.86	0.52 to 0.75
Fully adjusted¶	1	1.07	0.96	0.78	0.69
95% CIs		0.93 to 1.23	0.83 to 1.11	0.65 to 0.92	0.57 to 0.83

*HRs by Cox regression. The crude estimates were calculated by logistic regression and the risk estimates were ORs.

§Adjusted only for age, smoking and parity.

^¶Additionally adjusted for plurality.

BMI, body mass index; NA, not applicable.