Therefore, not all compromised pregnancies in this population share a common birthweight-specific mortality curve.
The framework developed in this paper does not require infants from compromised pregnancies to share a common birthweight-specific mortality curve, much less assume the existence of an interval of birthweights over which all infants have the same curve.
Yet, implicit in the 2-component normal mixture is a belief that all compromised pregnancies are qualitatively similar, in the sense of sharing a common birthweight-specific mortality curve.
Since components 2 and 4 in this population most plausibly consist of compromised pregnancies, we see that infants from compromised pregnancies need not share a common birthweight-specific mortality curve.
A 2-component normal mixture model assumes that infants from compromised pregnancies share a common birthweight-specific mortality curve, while a contaminated normal model assumes that all infants share a common curve over some (possibly quite large) interval of birthweights.
In the USA maternal report and self-report have been the most common sources of birthweight information, rather than birth records.
Suboptimal growth is common in very low birthweight infants (VLBWI) [ 6, 7] especially in those under 26 weeks [ 8].
15 As flagged values, indicating low scores, were common in this low birthweight population we corroborated these against paper records and infant growth trajectories.
Low birthweight is more common among the poorest and among ethnic minorities.
Preterm birth and low birthweight were more common in minority ethnic groups, especially in babies born to Bangladeshi women.
A recent meta-analysis revealed that in published studies of singleton births controlled for effects of maternal age, low birthweight was more common among those conceived by IVF (McDonald et al. 2009).
