Table 2.
Summary level Mendelian randomisation results for health behaviours on age at first birth, number of children and number of miscarriages
| Exposure | Outcome | Method | N SNP | Beta (95% CI) | P |
|---|---|---|---|---|---|
| Drinks per week | Age at first birth | IVW | 94 | − 0.055 (− 0.145, 0.034) | 0.22 |
| MR Egger | 94 | 0.04 (− 0.095, 0.175) | 0.56 | ||
| Weighted median | 94 | − 0.048 (− 0.139, 0.042) | 0.30 | ||
| Weighted mode | 94 | − 0.046 (− 0.129, 0.038) | 0.29 | ||
| Number of children | IVW | 83 | 0.027 (− 0.057, 0.110) | 0.53 | |
| MR Egger (SIMEX) | 83 | 0.014 (− 0.029, 0.058) | 0.52 | ||
| Weighted median | 83 | − 0.010 (− 0.094, 0.074) | 0.82 | ||
| Weighted mode | 83 | 0.009 (− 0.068, 0.086) | 0.82 | ||
| Number of miscarriages | IVW | 94 | − 0.029 (− 0.097, 0.038) | 0.39 | |
| MR Egger | 94 | − 0.018 (− 0.121, 0.084) | 0.73 | ||
| Weighted median | 94 | 0.001 (− 0.099, 0.102) | 0.98 | ||
| Weighted mode | 94 | 0.01 (− 0.084, 0.103) | 0.84 | ||
| Caffeine | Age at first birth | IVW | 6 | − 0.036 (− 0.13, 0.057) | 0.45 |
| Weighted median | 6 | 0.013 (− 0.073, 0.099) | 0.77 | ||
| Weighted mode | 6 | 0.033 (− 0.067, 0.134) | 0.54 | ||
| Number of children | IVW | 6 | 0.021 (− 0.031, 0.073) | 0.43 | |
| Weighted median | 6 | 0.021 (− 0.047, 0.089) | 0.54 | ||
| Number of miscarriages | IVW | 6 | − 0.042 (− 0.106, 0.022) | 0.20 | |
| Weighted median | 6 | − 0.052 (− 0.128, 0.025) | 0.19 | ||
| Weighted mode | 6 | − 0.076 (− 0.178, 0.025) | 0.20 | ||
| Smoking initiation | Age at First Birth | IVW | 322 | − 0.661 (− 0.757, − 0.566) | 3.57 × 10−42 |
| Weighted median | 322 | − 0.504 (− 0.603, − 0.405) | 2.71 × 10−23 | ||
| Weighted mode | 322 | − 0.555 (− 0.785, − 0.326) | 3.30 × 10−6 | ||
| Number of children | IVW | 323 | 0.280 (0.205, 0.355) | 3.17 × 10−13 | |
| Weighted median | 323 | 0.207 (0.125, 0.289) | 7.11 × 10−07 | ||
| Weighted mode | 323 | 0.177 (− 0.009, 0.363) | 0.06 | ||
| Number of miscarriages | IVW | 322 | − 0.123 (− 0.182, − 0.064) | 4.68 × 10−5 | |
| Weighted median | 322 | − 0.106 (− 0.196, − 0.017) | 0.019 | ||
| Weighted mode | 322 | − 0.176 (− 0.399, 0.047) | 0.124 | ||
| BMI | Age at first birth | IVW | 95 | − 0.108 (− 0.16, − 0.056) | 4.32 × 10−05 |
| MR Egger | 95 | − 0.076 (− 0.225, 0.072) | 0.32 | ||
| Weighted median | 95 | − 0.043 (− 0.101, 0.015) | 0.14 | ||
| Weighted mode | 95 | 0.006 (− 0.114, 0.126) | 0.92 | ||
| Number of children | IVW | 91 | − 0.014 (− 0.054, 0.027) | 0.51 | |
| MR Egger | 91 | − 0.002 (− 0.117, 0.113) | 0.98 | ||
| Weighted median | 91 | − 0.008 (− 0.054, 0.038) | 0.73 | ||
| Weighted mode | 91 | − 0.013 (− 0.094, 0.069) | 0.76 | ||
| Number of miscarriages | IVW | 95 | 0.004 (− 0.033, 0.041) | 0.83 | |
| MR Egger | 95 | 0.021 (− 0.086, 0.128) | 0.70 | ||
| Weighted median | 95 | 0.019 (− 0.033, 0.072) | 0.47 | ||
| Weighted mode | 95 | 0.013 (− 0.091, 0.116) | 0.81 |
IVW, inverse-variance weighted; BMI, body mass index. The I2GX suggested that the smoking initiation and caffeine genetic instruments were not suitable for conducting MR Egger (Additional file 1: Table S21). Unweighted SIMEX corrections were conducted for smoking initiation. Age at first birth and number of miscarriages are in females only. Number of children is in males and females combined