The mean birthweight in this study was 3.05 kg and 3.04 kg in men and women respectively.
Smoking was more common in the Thai cohort (~38 % vs. 19%% in PNG) where it reduced mean birthweight, whilst the habit was not associated with lower mean birthweight in the present study (−29 g, P = 0.30).
It is plausible that smoking was not associated with birthweight in this study, and another study from the same area [ 15], because of infrequent consumption or type of tobacco used.
Perinatal outcomes included gestational hypertension/preeclampsia, gestational diabetes mellitus, preterm delivery, cesarean delivery, birthweight <2500 g, and birthweight >4000 g.In the study population of 3779 Asian American women, there were statistically significant differences (P <.01) between most of the outcomes that were examined.
The mean neonatal birthweight was higher in the study group, but the difference was not significant (2550 g versus 1883 g, p = 0.14).
Furthermore, we registered all vaccinations given daily at the local health centres in the Bandim Health Project study area, and the vaccination cards of low birthweight children living in the study area were inspected at the routine home visits every three months.
In another sensitivity analysis, we compared the adjusted odds ratios (aORs) of MMMI and PMMI in subgroups using birthweight percentile of the study population as cut-off points, the results were essentially unchanged (data not shown).
The birthweight of cohort members who participated in the study was similar to that of persons who did not participate (3350 versus 3344 g, P = 0.8).
In addition to the equation-derived global reference birthweight percentiles, we also used the empirical country- and gestational-age-specific birthweight percentile of the study population as cut-off points.
