Prospective cohort study of factors influencing the relative weights of the placenta and the newborn infant.
OBJECTIVE
To determine the demographic, environmental, and medical factors that influence the relative weights of the newborn infant and the placenta and compare this ratio with other factors known to predispose to adult ill health.


METHODS
Prospective cohort study.


METHODS
The tertiary referral centre for perinatal care in Perth, Western Australia.


METHODS
2507 pregnant women who delivered a single live infant at term.


METHODS
Placental weight, birth weight, and the ratio of placental weight to birth weight.


RESULTS
By multiple regression analysis the placental weight to birthweight ratio was significantly and positively associated with gestational age, female sex, Asian parentage, increasing maternal body mass index, increased maternal weight at booking, lower socioeconomic status, maternal anaemia, and increasing number of cigarettes smoked daily. There were no consistent relations between the placental weight to birthweight ratio and measures of newborn size.


CONCLUSIONS
The ratio of placental weight to birth weight is not an accurate marker of fetal growth. In its role as a predictor of adult disease the ratio may be acting as a surrogate for other factors which are already known to influence health and may act before or after birth. Determining the role that relative growth rates of the fetus and placenta have in predisposing to adult disease requires prospective study to account for the many confounding variables which complicate this hypothesis.
Williams
L A
LA
Women and Infants Research Foundation, University of Western Australia, King Edward Memorial Hospital, Subiaco.
Evans
S F
SF
Newnham
J P
JP
D000328:Adult; D001208:Asia / Q000208:ethnology; D001724:Birth Weight; D015992:Body Mass Index; D001835:Body Weight; D015331:Cohort Studies; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D009929:Organ Size; D010920:Placenta / Q000033:anatomy & histology; D010929:Placentation; D011247:Pregnancy; D011446:Prospective Studies; D012737:Sex Factors; D012907:Smoking / Q000503:physiopathology; D014904:Western Australia / Q000453:epidemiology