Strong upward neighborhood mobility and preterm birth: a matched-sibling design approach

Much cross-sectional work reports an association between neighborhood disadvantage and adverse birth outcomes. Limitations of this work include that mothers with pre-existing unmeasured morbidity may "select" into, or out of, certain neighborhoods. This selection issue remains a key rival explanation for work concerned with place-based disparities in birth outcomes. We move beyond a cross-sectional approach and exploit a sibling-linked data set in California to test whether upwardly mobile mothers, who move from a very high to a very low disadvantaged neighborhood, exhibit a lower than expected risk of preterm birth (PTB) (i.e., delivery <37 weeks).

We used a matched-sibling design for 461,061 sibling pairs (i.e., 922,122 births total) to mothers in urban areas in who gave birth in California from 2005 to 2010. We linked mother's address at two time points (i.e., two sibling birth dates) to a census-derived composite indicator of neighborhood disadvantage. Conditional logistic regression methods controlled for mother's risk of PTB in the sibling delivered before the move when estimating the relation between strong upward mobility and preterm of the subsequent birth after the move.

As hypothesized, strong upward mobility (relative to no mobility) varies inversely with the odds of PTB of the second sibling (odds ratio [OR] for PTB = 0.83, 95% confidence interval: 0.74, 0.93).

Mothers moving from very high to very low disadvantaged neighborhoods show a reduced odds of PTB. Our findings, if replicated, raise the possibility that improvements in neighborhood quality may improve perinatal health in a relatively short time span.