TABLE 3—

Adjusted Risk Factors for Inadequacy of Prenatal Care Use: Ribeirão Preto, Brazil, 1978–1979 and 1994

	Adjusted Risk Ratio (95% Confidence Interval)a
	1978–1979	1994
Maternal age, y
< 20	1.36 (1.26, 1.48)	1.56 (1.27, 1.92)
20–34	1.00	1.00
≥ 35	0.89 (0.80, 1.00)	0.78 (0.55, 1.10)
Parity
1	0.75 (0.70, 0.81)	0.74 (0.60, 0.91)
2–4	1.00	1.00
≥ 5	1.33 (1.22, 1.44)	1.56 (1.19, 2.04)
Marital status
Married	1.00	1.00
Cohabiting	1.44 (1.34, 1.55)	1.85 (1.50, 2.29)
Single	1.67 (1.54, 1.82)	1.77 (1.36, 2.32)
Maternal education, y
≤ 4	1.69 (1.43, 2.00)	2.23 (1.07, 4.63)
5–11	1.35 (1.15, 1.59)	1.64 (0.81, 3.32)
≥ 12	1.00	1.00
Type of insurance
Private	1.00	1.00
Public	1.31 (1.09, 1.58)	5.96 (3.75, 9.45)
Maternal smoking
No	1.00	1.00
Yes	1.31 (1.00, 1.14)	1.39 (1.17, 1.65)

Note. Subjects with missing information on gestational age and prenatal care were excluded from this analysis.

^aCox regression was used to adjust risk ratios for all factors shown in table assuming equal duration of follow-up for all subjects and robust estimates of standard error would occur.