Table 1

Characteristics of boys and girls from the third generation Uppsala Birth Cohort Multigeneration Study born in 1973–81 (N=10 835)

	Births^*		Preterm Births^*		Grade in Swedish^†
	n	(%)	n	(%)	1, 2 (low)	3 (medium)	4, 5 (high)
Maternal age at birth, years
15–19	560	5.2	40	7.2	34.9	43.4	21.7
20–24	3664	33.8	149	4.1	23.7	46.1	30.1
25–29	4627	42.7	166	3.6	17.1	42.9	40.0
30–34	1726	15.9	65	3.8	14.8	40.9	44.3
35–42	257	2.4	17	6.7	15.5	41.1	43.5
Missing	1	0.0	–	–
Parity
1	5030	46.4	207	4.1	17.0	42.2	40.8
2	4104	37.9	156	3.8	21.2	44.9	33.9
3+	1642	15.2	74	4.5	25.3	44.9	29.8
Missing	59	0.5	–	–	18.9	49.1	32.1
Preterm birth (<37 weeks)
No	10305	95.1			19.6	43.7	36.7
Yes	437	4.0			26.6	41.9	31.5
Missing	193	0.9			14.3	46.4	39.3
Fetal growth (quintiles)
1	2141	19.8	67	3.1	22.7	46.5	30.7
2	2137	19.7	94	4.4	21.8	42.1	36.1
3	2151	19.9	186	4.9	17.8	45.4	36.8
4	2151	19.9	93	4.3	18.6	42.7	38.7
5	2157	19.9	15	3.5	18.5	41.5	40.0
Missing	98	0.1	–	–	17.2	44.8	37.9
Gender
Boy	5515	51.0	248	4.5	29.9	46.5	23.6
Girl	5320	49.0	189	3.6	9.5	40.8	49.8
Parental education
Concordant low	4742	43.8	197	4.2	29.6	47.7	22.8
Discordant	2962	27.3	119	4.0	16.8	46.4	36.9
Concordant high	2939	27.1	113	3.9	7.0	34.7	58.4
Missing	192	1.8	–	–	29.0	42.0	29.0
Grade in Swedish 9th grade
1	174	1.6	9	5.2
2	1909	17.6	101	5.3
3	4581	42.3	173	3.8
4	3140	29.0	107	3.4
5	690	6.4	23	3.4
Missing	341	3.2	–	–
Total	10835			4.0	19.9	43.7	36.5

↵* Percentage run down the column.
↵† Percentage run across the column.