Table 3.

RRcs and RRas and 95% CIs for Mental Retardation and Several Infant and Maternal Characteristics, California 1987–1994

Mild MR
(n = 5028)*
Severe MR
(n = 1536)*
Unspecified Level of MR
(n = 1219)*
RRc95% CIRRa95% CIRRc95% CIRRa95% CIRRc95% CIRRa95% CI
Child sex
 Female1.0Reference1.0Reference1.0Reference1.0Reference1.0Reference1.0Reference
 Male1.91.8–2.01.91.8–2.01.31.2–1.51.41.2–1.51.61.4–1.81.61.5–1.8
Birth weight
 ≥2500 g1.0Reference1.0Reference1.0Reference1.0Reference1.0Reference1.0Reference
 <2500 g4.94.6–5.24.34.0–4.64.33.8–4.94.33.8–4.95.65.0–6.45.44.7–6.2
Plurality
 Singleton1.0Reference1.0Reference1.0Reference1.0Reference1.0Reference1.0Reference
 Multiple3.02.7–3.31.21.1–1.41.71.3–2.20.70.6–1.02.82.2–3.51.00.8–1.3
Parity
 11.0Reference1.0Reference1.0Reference1.0Reference1.0Reference1.0Reference
 21.21.1–1.21.11.1–1.21.11.0–1.31.10.9–1.21.11.0–1.31.21.0–1.3
 ≥31.61.5–1.71.31.2–1.51.51.3–1.61.11.0–1.31.61.4–1.91.51.3–1.8
Maternal age
 <201.0Reference1.0Reference1.0Reference1.0Reference1.0Reference1.0Reference
 20–240.90.9–1.01.11.0–1.21.10.9–1.31.31.1–1.60.90.8–1.11.00.8–1.2
 25–290.90.8–1.01.11.0–1.31.10.9–1.31.41.1–1.71.00.8–1.21.00.8–1.2
 30–340.90.9–1.01.31.1–1.41.10.9–1.41.61.3–1.91.21.0–1.41.10.9–1.5
 ≥351.00.9–1.21.41.2–1.61.41.2–1.81.91.5–2.41.21.0–1.61.20.9–1.5
Maternal education
 <High school1.0Reference1.0Reference1.0Reference1.0Reference1.0Reference1.0Reference
 High school1.00.9–1.00.70.7–0.80.80.7–0.90.70.6–0.81.00.8–1.10.80.7–1.0
 College0.70.6–0.70.50.5–0.60.60.5–.070.60.5–0.70.90.8–1.00.70.6–0.9
 Postgraduate0.40.3–0.50.30.3–0.40.40.3–0.60.40.3–0.60.80.6–1.00.70.5–0.9
Maternal birth place
 California1.0Reference1.0Reference1.0Reference1.0Reference1.0Reference1.0Reference
 United States, not California0.80.7–0.80.80.7–0.81.00.8–1.11.00.8–1.10.90.8–1.10.90.7–1.0
 Mexico0.70.6–0.70.60.5–0.61.21.1–1.30.90.8–1.10.70.6–0.80.80.6–0.9
 Other0.60.6–0.70.70.6–0.81.10.9–1.20.90.8–1.10.90.7–1.00.80.7–1.0
Maternal race/ethnicity
 White1.0Reference1.0Reference1.0Reference1.0Reference1.0Reference1.0Reference
 Hispanic1.00.9–1.00.90.8–1.01.41.3–1.61.21.0–1.40.90.8–1.00.80.7–1.0
 Black2.11.9–2.31.51.4–1.72.01.7–2.41.61.4–1.91.71.4–2.01.21.0–1.5
 Asian0.60.5–0.70.70.6–0.81.41.1–1.81.31.0–1.71.20.9–1.51.20.9–1.6
  • RRc indicates crude rate ratio, RRa, adjusted rate ratio, adjusted for all other variables in the table; CI, confidence interval.

  • * Only children with nonmissing values on all variables in the table are included.