Table 2.

Risk (OR) of overall congenital malformations according to characteristics of fever in 1st trimester

	N	N Cases	Congenital Malformations OR Crude [95% CI]	Congenital Malformations Adjusted* OR [95% CI]
Fever
No	69,023	2574	1 [Ref]	1 [Ref]
Yes	8321	302	0.97 [0.86–1.10]	0.99 [0.88 1.12]
Gestational age at fever incidents
No fever	69,023	2574	1 [Ref]	1 [Ref]
Pregnancy week 1–4	1032	43	1.12 [0.82–1.52]	1.13 [0.83–1.54]
Pregnancy week 5–8	3407	124	0.98 [0.81–1.17]	0.99 [0.83–1.19]
Pregnancy week 9–12	3882	135	0.93 [0.78–1.11]	0.95 [0.79–1.13]
Maximum temperature
No fever	69,023	2574	1 [Ref]	1 [Ref]
< 39.0 ° C	2613	108	1.11 [0.91–1.35]	1.12 [0.91–1.36]
≥ 39.0 ° C	2562	98	1.03 [0.84–1.26]	1.06 [0.86–1.30]
Unknown	3146	96	0.81 [0.66–1.00]	0.82 [0.67–1.01]
Duration of fever episode
No fever	69,023	2574	1 [Ref]	1 [Ref]
1 day	1647	55	0.89 [0.68–1.17]	0.90 [0.69–1.18]
2–3 days	4799	180	1.01 [0.86–1.17]	1.02 [0.88–1.19]
+ 4 days	1873	67	0.96 [0.75–1.23]	0.98 [0.76–1.25]
Unknown	2	0	..	..

The Danish National Birth Cohort 1996–2002

*Adjusted for parity, previous spontaneous abortion, maternal age at conception, IVF, diabetes mellitus, medical treatment of maternal epilepsy, rheumatoid arthritis, binge drinking in first trimester, smoking during pregnancy, and socio-occupational status