Introduction
Methods
Participants
Measures
Statistical analysis
Results
Descriptives
N
| Mean | Standard deviation | |
---|---|---|---|
First-born twin birth-weight | 889 | 2484.55 | 544.03 |
Second-born twin birth-weight | 889 | 2457.62 | 562.17 |
MZ first-born birth-weight | 381 | 2404.32 | 531.55 |
MZ second-born birth-weight | 381 | 2392.41 | 545.44 |
DZ first-born birth-weight | 508 | 2544.65 | 546.01 |
DZ second-born birth-weight | 508 | 2506.10 | 570.11 |
Girl first-born birth-weight | 489 | 2445.43 | 544.59 |
Girl second-born birth-weight | 489 | 2426.00 | 560.75 |
Boy first-born birth-weight | 400 | 2532.18 | 540.06 |
Boy second-born birth-weight | 400 | 2494.76 | 562.45 |
MZ duration of gestation (weeks) | 371 | 36.44 | 3.00 |
DZ duration of gestation (weeks) | 497 | 35.99 | 2.75 |
Girls weeks gestation | 483 | 36.31 | 2.87 |
Boys weeks gestation | 385 | 36.18 | 2.87 |
Main effect of birth-weight for gestation—standard regression analysis
Genetic regression analysis
Beta (birth-weight as a continuous variable) | P value | Beta (low birth-weight for gestation as a categorical variable) | P value | |
---|---|---|---|---|
Interaction between birth-weight corrected for gestation & genetic risk | −0.048a
| 0.096 | 0.394*
| 0.001 |
Birth-weight for gestation | −0.081*
| 0.006 | −0.075*
| 0.032 |
Co-twin depressive symptoms | 0.541*
| 0.001 | 0.212*
| 0.002 |
Twin gender | 0.044a
| 0.130 | 0.049a
| 0.080 |
Zygosity | 0.027 | 0.349 | −0.096*
| 0.010 |
Maternal pre-natal smoking (yes/no) | 0.063*
| 0.033 | 0.067*
| 0.021 |
Social class | 0.011 | 0.705 | 0.011 | 0.700 |
Maternal age at birth | −0.024 | 0.411 | −0.018 | 0.529 |