Table 2

Comparison of BW from the CSHRR and the MBR stratified by birth year groups according to MBR procedural changes and by maternal and offspring characteristics

	N	Birth weight (grams)				p Value*
		CSHRR		MBR
		Mean	SD	Mean	SD
1973–1978
All	15 807	3323	555	3036	558	<0.0001
Boys	7980	3382	568	3092	569	<0.0001
Girls	7827	3263	535	2980	540	<0.0001
1979–1990
All	28 708	3348	568	3346	555	0.67
Boys	14 782	3409	580	3407	566	0.67
Girls	13 926	3283	547	3282	535	0.86
1991
All	3 019	3389	577	3391	564	0.67
Boys	1540	3446	587	3446	578	0.98
Girls	1479	3330	560	3332	542	0.90
Maternal characteristics†
Maternal age (years)
<20	1187	3252	543	3244	518	0.69
20–30	19 183	3337	554	3334	542	0.58
30–40	10 772	3387	592	3388	579	0.87
40–50	582	3401	603	3406	587	0.89
≥50	3	3292	525	3290	524	0.99
Civil status
Married	16 533	3369	576	3367	559	0.68
Divorced	1 970	3320	593	3321	584	0.98
Not married	13 224	3335	555	3334	547	0.90
Parity
1	17 219	3308	555	3304	544	0.49
2	10 101	3400	575	3402	561	0.84
3	2976	3403	582	3402	559	0.99
4	892	3439	623	3430	604	0.76
5	332	3422	589	3441	566	0.68
≥6	207	3436	626	3453	614	0.78
Offspring characteristics†
Year of birth
1979–81	6607	3322	565	3322	552	0.99
1982–84	6248	3306	577	3305	565	0.91
1985–87	7591	3344	566	3341	550	0.75
1988–91	11 281	3401	565	3399	554	0.78
Age at recall (years)
5–6	2984	3381	556	3379	541	0.87
6–6.5	9662	3363	563	3362	550	0.90
6.5–7	10 410	3355	564	3354	554	0.93
7–8	7245	3327	582	3323	565	0.65
>8	1316	3326	598	3328	579	0.94
BMI classification at BW recall
Underweight	2384	3100	592	3097	576	0.88
Normal weight	25 186	3358	558	3357	545	0.88
Overweight	3104	3468	560	3462	541	0.68
Obese	542	3514	614	3507	598	0.84
Morbidly obese	401	3378	622	3360	597	0.68

*Comparisons made by paired t tests.
†Comparisons of mean BW by maternal and offspring characteristics are only presented for the period 1979–1991.
BMI, body mass index; BW, birth weight; CSHRR, Copenhagen School Health Records Register; MBR, Medical Birth Register.