Table 1.
Characteristics of mother-child pairs, according to maternal urinary cotinine in pregnancy
| Cotinine categoriesa |
|||||
|---|---|---|---|---|---|
| Total (n = 622) | No exposure (n = 457) | Secondhand smoke (n = 130) | Active smoker (n = 35) | p-value | |
| Maternal characteristics | |||||
| Maternal age, yrs | 29 ± 6 | 30 ± 5 | 24 ± 6 | 27 ± 5 | <0.01 |
| Gestational weight gain, kg | 14 ± 6 | 14 ± 6 | 14 ± 7 | 14 ± 8 | 0.97 |
| Pre-pregnancy BMI, kg/m2 | 25 ± 6 | 25 ± 6 | 26 ± 6 | 26 ± 8 | 0.11 |
| Gravidity, number of pregnancies | 1.4 ± 1.5 | 1.3 ± 1.4 | 1.3 ± 1.5 | 2.2 ± 1.7 | <0.01 |
| Maternal diet quality during pregnancy, HEI-2010 scores | 62 ± 11 | 64 ± 10 | 56 ± 10 | 52 ± 10 | <0.01 |
| Maternal Race/Ethnicity | |||||
| Non-Hispanic white | 56% | 64% | 31% | 40% | |
| Non-Hispanic black | 11% | 5% | 31% | 34% | |
| Hispanic | 26% | 26% | 28% | 17% | |
| Other | 6% | 5% | 9% | 9% | <0.01 |
| Household income | |||||
| <$40,000 | 26% | 20% | 44% | 49% | |
| $70,001 to $70,000 | 19% | 21% | 12% | 26% | |
| >$70,000 | 37% | 47% | 9% | 9% | |
| Don’t know | 18% | 13% | 35% | 17% | <0.01 |
| Mother’s highest level of education | |||||
| <12 years | 13% | 8% | 27% | 26% | |
| High school degree | 16% | 11% | 32% | 25% | |
| College classes or college degree | 71% | 81% | 40% | 51% | <0.01 |
| Offspring characteristics | |||||
| Male offspring | 51% | 51% | 49% | 50% | 0.5 |
| Gestational age at birth, wks | 40 ± 1 | 40 ± 1 | 39 ± 1 | 39 ± 1 | 0.32 |
| Age at introducion of solid foods | |||||
| ≥4 months | 96% | 98% | 92% | 94% | |
| <4 months | 4% | 2% | 8% | 6% | <0.01 |
| Duration of exclusive breastfeeding (n = 545) | |||||
| ≥5 months | 47% | 56% | 25% | 0% | |
| <5 months | 53% | 44% | 75% | 100% | <0.01 |
| Exposure to secondhand smoke at age 5 months (n = 569) | |||||
| No household smokers | 86% | 96% | 63% | 20% | |
| Any household smokers | 14% | 4% | 37% | 80% | <0.01 |
Continuous variables are expressed as means ± standard deviation. One-way analysis by variance (ANOVA) tests were used to examine differences in means across the urinary cotinine categories. Categorical variables are expressed as proportions of column totals. Chi-square tests were used to examine differences in proportions across the urinary cotinine categories
BMI body mass index, LOD limit of detection
a
The cotinine categories were defined as follows: no exposure (<0.05 ng/ml [LOD]), exposure to secondhand smoke (≥LOD & <550 ng/mL) and active smoker (≥550 ng/mL).