Table 2 Risk ratios (95% confidence intervals) for associations between preterm birth and covariates among PROTECT participants in fully-adjusted modified Poisson modela
From: Preterm birth and PM2.5 in Puerto Rico: evidence from the PROTECT birth cohort
Covariate | RR (95% CI) | p-value |
|---|---|---|
Individual-level covariates | ||
Infant sex | ||
Female | 1.00 (Ref) | |
Male | 1.18 (0.77, 1.81) | 0.460 |
Mother’s age (years) | 1.05 (1.00, 1.09) | 0.035 |
Number of pregnancies, including this one | ||
This one only | 1.00 (Ref) | |
Have had other pregnancies | 0.74 (0.42, 1.29) | 0.282 |
Mother’s education | 0.688 | |
College | 1.00 (Ref) | |
High school or technical school | 1.26 (0.73, 2.20) | |
Less than high school | 1.38 (0.56, 3.38) | |
Marital status at first study visit | ||
Married | 1.00 (Ref) | |
Single, divorced, or cohabiting | 1.78 (1.14, 2.78) | 0.012 |
Employed at first study visit | ||
Yes | 1.00 (Ref) | |
No | 1.66 (0.95, 2.89) | 0.074 |
Family income per year, US dollars | ||
< 30,000 | 1.00 (Ref) | |
≥ 30,000 | 0.93 (0.54, 1.58) | 0.777 |
Mother’s race | ||
Hispanic white | 1.00 (Ref) | |
Black or other race | 1.28 (0.84, 1.95) | 0.247 |
History of adverse pregnancy outcomes | ||
No | 1.00 (Ref) | |
Yes | 1.37 (0.79, 2.35) | 0.258 |
Any cigarette smoke exposure in the home | ||
No | 1.00 (Ref) | |
Yes | 1.01 (0.61, 1.67) | 0.984 |
Alcohol consumption in past year, days per week | ||
0 | 1.00 (Ref) | |
1 or more | 0.70 (0.34, 1.45) | 0.339 |
Delivery type | ||
Vaginal | 1.00 (Ref) | |
Caesarian | 1.55 (0.99, 2.43) | 0.057 |
Exercise habits | ||
Not exercise for > 30 min/day in past 3 months | 1.00 (Ref) | |
Exercised for > 30 min/day in past 3 months | 0.94 (0.57, 1.57) | 0.821 |
Maternal pre-pregnancy BMI | 0.059 | |
Normal or underweight | 1.00 (Ref) | |
Overweight | 1.66 (1.02, 2.68) | |
Obese | 1.70 (1.00, 2.89) | |
Municipal-level covariates | ||
Household income, 2013 inflation-adjusted US dollars | ||
Below median for PR (USD 22,754) | 1.00 (ref) | |
Above median | 1.00 (1.00, 1.00) | 0.343 |
Population density | ||
≤ median for PR (2760/mile2) | 1.00 (ref) | |
> median | 1.00 (1.00, 1.00) | 0.159 |
% adults (> 25 yr) with < high school education | ||
≤ median for PR (23.9%) | 1.00 (ref) | |
> median | 1.07 (1.00, 1.14) | 0.052 |
% occupied units with 1 or more severe housing problemsb | ||
≤ median for PR (34.8%) | 1.00 (ref) | |
> Above median | 0.99 (0.96, 1.03) | 0.597 |
% non-white, non-Hispanic population | ||
≤ median for PR (35.7%) | 1.00 (ref) | |
> median | 1.02 (0.99, 1.06) | 0.252 |
Average unemployment rate, 2004–2013 | ||
≤ median for PR (10.3%) | 1.00 (ref) | |
> median | 1.07 (0.85, 1.35) | 0.555 |
Age adjusted diabetes prevalence, 2004–2013 | ||
≤ median for PR (12.4%) | 1.00 (ref) | |
> median | 2.19 (1.00, 4.79) | 0.051 |