Causal models for monitoring the progress of infants
with low birthweight
N. T. Longford, Oscar Ramirez and Cindy Giffe
Abstract
We study the weight (body mass) of infants born prematurely
and with low birthweight during the first year of their lives.
The infants are enrolled in the Casa Canguro programme in Valle de Cauca,
a department (province) of Colombia.
The current weight and other physiological measurements are recorded
at their visits to participating health-care facilities.
We compare two groups of infants: those born at 31 weeks of gestational age
or earlier (extremely preterm) and those born at 33 weeks or later (preterm).
The comparisons are made within the potential outcomes framework,
regarding the two groups as treatments, as an alternative to adjustment
for an extensive set of covariates.
Matching is accomplished by propensity scoring.
The outcomes (weight and height) at a particular age
are approximated by interpolation.
We conclude that the weight-handicap of the extremely preterm infants
first increases, from about 600 grams at birth to 900 grams on average
at three months, and then is reduced, so that by the first birthday
they are only about 250 grams lighter on average.
Revista Brasileira de Estadistica (Brazilian Biometric Journal); to appear.
November 2016