Table 1 Descriptive statistics of the ALSPAC and the MoBa cohort samples used for the analysis. For the continuous variables mean and standard derivation are displayed. For the categorical variables a percentage is given. If there are two variable descriptions given in one row, then the first one corresponds to the ALSPAC study and the second one to the MoBa study
From: Smoking during pregnancy and its effect on placental weight: a Mendelian randomization study
Variable | Mean (SD) / Percentage | N without missing | ||
|---|---|---|---|---|
Study | ALSPAC | MoBa | ALSPAC | MoBa |
Birth weight (g) | 3402 (486) | 3674 (484) | 2346 | 4770 |
Placental weight (g) | 654 (131) | 689 (145) | 804 | 4667 |
Gestational duration (weeks in ALSPAC/days in MoBa) | 39.8 (1.3) | 282 (9) | 2346 | 4776 |
Mothers age (years) | 26.8 (5) | 28.7 (4.7) | 2346 | 4776 |
Mothers height (cm) | 164 (7) | 168.3 (5.8) | 2102 | 4735 |
Mothers pre-pregnancy weight/ at the beginning of pregnancy (kg) | 62 (11) | 69 (13) | 2011 | 4660 |
Offspring (male %) | 50.8 | 50.3 | 2346 | 4776 |
Smoking in the first three month of pregnancy/ Smoking at the beginning of pregnancy (yes %) | 72.4 | 35 | 2346 | 4715 |
Smoking in the last two weeks of pregnancy/Smoking at the end of pregnancy (yes %) | 57.9 | 17.5 | 2032 | 4580 |
Year of delivery | 1991–1993 | 1999–2009 | 2346 | 4776 |