. Author manuscript; available in PMC: 2016 Jan 31.

Published in final edited form as: BJOG. 2014 Jun 20;122(3):420–428. doi: 10.1111/1471-0528.12930

Table 2. First trimester coffee and tea consumption and adjusted risk ratios (95% confidence intervals) for gestational diabetes mellitus in the Danish National Birth Cohort, 1996-2002.

	Overall (n=71,239)					Stratified by Smoking Status
	Overall (n=71,239)					Non-Smokers (n=52,629)					Smokers (n=18,610)
Cups/ d	GDM Cases^a	(%)	aRR^b	95% CI	P^c	GDM Cases^a	(%)	aRR^d	95% CI	P^c	GDM Cases^a	(%)	aRR^d	95% CI	P^c
Coffee					.16					.05					.91
0	500	(1.27)	1.00	Referent		389	(1.22)	1.00	Referent		111	(1.50)	1.00	Referent
½ – 3	280	(1.24)	0.97	0.84, 1.13		196	(1.21)	0.97	0.81, 1.15		84	(1.35)	0.99	0.75, 1.32
4 – 7	90	(1.29)	0.81	0.64, 1.02		41	(1.12)	0.76	0.55, 1.05		49	(1.48)	0.86	0.61, 1.22
≥8	42	(1.76)	0.89	0.64, 1.25		19	(2.54)	1.45	0.92, 2.30		23	(1.41)	0.69	0.44, 1.09
Tea					.31					.24					.79
0	381	(1.46)	1.00	Referent		249	(1.41)	1.00	Referent		132	(1.58)	1.00	Referent
½ – 3	376	(1.17)	0.91	0.79, 1.05		296	(1.17)	0.94	0.79, 1.11		80	(1.16)	0.81	0.62, 1.07
4 – 7	118	(1.19)	0.88	0.72, 1.08		77	(1.02)	0.78	0.60, 1.01		41	(1.74)	1.16	0.82, 1.64
≥8	37	(1.20)	0.77	0.55, 1.08		23	(1.10)	0.75	0.49, 1.14		14	(1.40)	0.81	0.47, 1.40

Abbreviations: aRR, adjusted risk ratio; CI, confidence interval; GDM, gestational diabetes mellitus.

GDM cases identified from Discharge Register or self-reported on either DNBC interview (n=912).

Model adjusted for coffee or tea consumption (categorical), as appropriate, age (categorical), socio-occupational status (categorical), parity (categorical), prepregnancy body mass index (categorical), smoking (categorical) and cola intake (categorical).

Represents P for linear trend.