Descriptive Statistics of the Main Analysis Sample (ALSPAC)
| Mean | SD | Min. | Max. | N | |
|---|---|---|---|---|---|
| Outcome Variable | |||||
| Birth weight (grams) | 3,406.24 | 556.60 | 703 | 5,600 | 7,598 |
| Main Explanatory Variables | |||||
| Smoking regularly | 0.22 | 0.42 | 0 | 1 | 7,417 |
| Smoking regularly (adjusted) | 0.31 | 0.46 | 0 | 1 | 2,777 |
| Number of cigarettes smoked per day | 2.02 | 5.09 | 0 | 51 | 7,598 |
| Number of cigarettes smoked per day (adjusted) | 4.96 | 6.64 | 0 | 51 | 3,784 |
| Cotinine (ng/mL) | 743.76 | 1,923.57 | 0 | 24,674 | 2,844 |
| Birth weight PGS (child) | 0.00 | 1.00 | –3 | 3 | 5,006 |
| Instrumental Variable | |||||
| rs1051730 | 0.67 | 0.67 | 0 | 2 | 7,598 |
| Control Variables | |||||
| Mother’s birth weight (grams) | 3,269.01 | 601.43 | 909 | 6,108 | 4,541 |
| Mother’s age (years) | 28.47 | 4.66 | 15 | 44 | 7,598 |
| Mother’s marital status (married = 1) | 0.78 | 0.41 | 0 | 1 | 7,540 |
| Mother’s education (categories) | 3.65 | 1.61 | 0 | 6 | 5,484 |
| Mother’s social class (categories) | 2.85 | 1.07 | 1 | 6 | 6,141 |
| Grandmother’s education (categories) | 2.45 | 1.29 | 1 | 5 | 4,267 |
Notes: SD, standard deviation; Min., minimum; Max., maximum; PGS, polygenic score.