Table 1.

Comparison of the characteristics of the participants at birth and school age.

Variables		Ribeirão	Preto				São	Luís
	n Initial sample (excluding 48 deaths)	n Eligible to follow-up	n followed up	% followed up	p*	n Initial sample (excluding 65 deaths)	n Eligible to follow-up	n followed up	% followed up	p*
Maternal age (years)					0.005					0.350
20 to 34	2051	832	563	67.7		1,577	610	442	72.5
≥35	265	114	94	82.5		101	41	32	78.0
<20	487	202	131	64.9		698	274	199	72.6
Missing	7	2	2	85.7		2	1	0	0.0
Marital status					< 0.001					0.670
Married	1,664	666	489	73.5		695	266	199	74.8
Cohabiting	690	291	158	54.2		1,107	437	314	71.9
Single	338	147	106	72.1		575	223	160	71.7
Missing	118	46	37	80.4		1	0	0	0.0
Maternal schooling (years)					< 0.001					<0.001
≥ 12	367	145	93	64.3		119	46	14	30.4
9 to 11	607	246	170	69.2		841	324	255	78.7
5 to 8	1,028	416	304	73.1		1007	397	301	75.8
≤ 4	618	267	158	59.1		405	157	103	65.6
Missing	190	76	65	85.2		6	2	0	0.0
Parity					0.361					0.049
1	1148	467	313	67.0		1156	457	316	69.1
2 to 4	1474	600	423	70.5		1119	424	321	75.7
≥ 5	160	73	46	63.0		103	45	36	80.0
Missing	28	10	8	80.0		0	0	0	0.0
Sex					0.714					0.001
Male	1425	581	402	69.2		1295	509	348	68.4
Female	1384	569	388	68.2		1083	417	325	77.9
Missing	1	0	0	0.0		0	0	0	0.0
Total	2810	1150	790	68.7		2378	926	673	72.7

Ribeirão Preto, 1994 and 2004/05 and São Luís, 1997/98 and 2005/06

* P value calculated by the chi-squared test.