Table 1.
Description of the Study Variables
| Variable | Definition | Mean (SD) |
|---|---|---|
| Cigarettes before pregnancy | Number of cigarettes per day smoked in the 12 months before pregnancy | 4.2 (6.4) |
| Cigarettes in the first trimester | Number of cigarettes per day smoked in the first trimester | 2.3 (4.3) |
| Maternal age | Maternal age in years | 29.3 (4.7) |
| Less than high schoola | Binary (0,1) indicator for maternal education of less than completed high school | 0.111 (0.314) |
| High schoola | Binary (0,1) indicator for maternal education of completed high school | 0.255 (0.436) |
| Technical collegea | Binary (0,1) indicator for mother attending technical college | 0.202 (0.402) |
| Universitya | Binary (0,1) indicator for mother completing university education | 0.064 (0.245) |
| Maternal employment | Binary (0,1) indicator for maternal employment in the first trimester | 0.839 (0.368) |
| Very low maternal incomeb | Binary (0,1) indicator for current gross maternal yearly income of less than 150,000 kr | 0.359 (0.48) |
| Moderate maternal incomeb | Binary (0,1) indicator for current gross maternal yearly income between 201,000 and 250,000 kr inclusive | 0.244 (0.43) |
| High maternal incomeb | Binary (0,1) indicator for current gross maternal yearly income of 251,000 kr or more | 0.141 (0.349) |
| Binge drinking in the first trimesterc | Binary (0,1) indicator for ≥ 4 drinks per drinking occasion in the first trimester | 0.06 (0.237) |
| Moderate drinking in the first trimesterc | Binary (0,1) indicator for 2–3 drinks per occasion in the first trimester | 0.092 (0.29) |
| Low drinking in the first trimesterc | Binary (0,1) indicator for 1 drink per occasion in the first trimester | 0.189 (0.392) |
| Multivitamin use | Binary (0,1) indicator for using multivitamins before and during the first two months of pregnancy | 0.359 (0.48) |
| Underweightd | Binary (0,1) indicator for maternal BMI prior to pregnancy of less than 18.5 | 0.03 (0.172) |
| Overweightd | Binary (0,1) indicator for maternal BMI prior to pregnancy between 25 and 29.9 inclusive | 0.19 (0.393) |
| Obesed | Binary (0,1) indicator for maternal BMI prior to pregnancy of greater than 29.9 | 0.079 (0.271) |
| Calories | Average daily calorie intake during the first trimester | 2244.6 (750.8) |
| Pregnancy planning | Binary (0,1) indicator for mothers who were planning to become pregnant | 0.735 (0.442) |
| rs1930139_BBe | Binary (0,1) indicator of AB genotype of rs1930139 | 0.327 (0.469) |
| rs1930139_ABe | Binary (0,1) indicator of BB genotype of rs1930139 | 0.051 (0.221) |
| rs1547272_BBe | Binary (0,1) indicator of AB genotype of rs1930139 | 0.345 (0.476) |
| rs1547272_ABe | Binary (0,1) indicator of BB genotype of rs1930139 | 0.06 (0.237) |
| rs1435252_AAf | Binary (0,1) indicator of AB genotype of rs1435252 | 0.082 (0.274) |
| rs1435252_ABf | Binary (0,1) indicator of BB genotype of rs1435252 | 0.405 (0.491) |
| rs2743467_BBe | Binary (0,1) indicator of AB genotype of rs2743467 | 0.43 (0.495) |
| rs2743467_ABe | Binary (0,1) indicator of BB genotype of rs2743467 | 0.11 (0.313) |
Note: The sample includes 856 observations.
a
The reference category is 2–4 years of college;
b
The reference category is 151,000–200,000 kr;
c
The reference category is no drinking;
d
The reference category is normal weight (18.5≤BMI<25);
e
The reference category for the SNP genotype indicators is the AA genotype;
f
The reference category for the SNP genotype indicator is the BB genotype.