Returns to birth weight in an egalitarian setting. Can parents mitigate negative effects of low birth weight?

Low birth weight as a marker of the prenatal environment has been identified as a strong predictor of long term health and development. This finding exemplifies research showing the long arm of early disadvantage. However, the... [ view full abstract ]

Low birth weight as a marker of the prenatal environment has been identified as a strong predictor of long term health and development. This finding exemplifies research showing the long arm of early disadvantage. However, the negative effect of low birth weight could in part be due to genetic and family environmental confounders. Relatively few studies use studies of twins and/or siblings to control for genetic and family confounders. Moreover, it is not clear how persistent the effects of early disadvantage are: they could be stable or even increasing over the life course (cumulative disadvantage), or early disadvantage could be mitigated over time. We argue that this may depend on parental behavior: parents may differentiate investments between siblings (twins) in order to reinforce or compensate initial differences. We hypothesize that higher SES parents are better able to reduce the negative effects of low birth weight than lower SES parents. The frequent occurrence of low birthweight among twins makes this an important area to investigate. Furthermore, differential treatment of twins has important bearings for twin research. We examine the effect of low birth weight on cognitive ability, height, and health in a new representative sample of twins and siblings from Germany (Twinlife). Currently we use the released first half of the first wave, which contains information on about 2,000 same-sex twin pairs. The first wave comprises 4 ages (5, 12, 17, 24). Preliminary results indicate that effects of birth weight remain even in within-MZ estimates. Future work will use the full sample (4,000 pairs) and also address the questions:

1. Are the effects of early disadvantage on children's development and health stable, reinforced, or mitigated over the life course?
2. How do parents influence whether early disadvantages are reinforced or mitigated?
   1. Do parents invest differently in their children depending on differences in birth weight within twin pairs?
   2. Are initial differences between twins/siblings more often compensated for by more resourceful parents?