Objective: To estimate the changes, in risk of intrapartum caesalrean delivery and perinatal distress that may be introduced through increased birth size, resulting from interventions such as improving nutrition of the mother; and to characterise delivery risk relative to maternal stature by birth size.
Design: Model these risks using data from the Guatemalan Perinatal Study.
Setting: The antenatal clinic of the Gynaecology and Obstetrics Hospital of the Guatemalan Social Security Institute in Guatemala City serving predominantly working class women.
Population: Women who had their first prenatal visit between April 1984 and January 1986.
Methods: Multivariate logistic regression models were developed to estimate incidence of intrapartum caesarean delivery and perinatal distress and used to calculate changes in risk associated with changes in size.
Main outcome measures: Incidences of intrapartum caesarean delivery and perinatal distress.
Results: A woman of 146cm height (-1 SD) relative to another of 160 cm (+1 SD) has a 2.5 times higher risk of intrapartum caesarean delivery. An increase in newborn head circumference and weight (from -1 SD to +1 SD) are each independently associated with an increase in risk of intrapartum caesarean delivery (2.0 times and 1.5 times. respectively). An increase in birthweight from 2,450 g to 2,550 g is associated with a decrease in risk of perinatal distress of 34/1,000 cases and an increase in risk of intrapartum caesarean delivery of 8/1,000 cases.
Conclusions: Increases in fetal growth comparable to those attributable to improved nutrition during pregnancy are associated with a larger decrease in risk of perinatal distress relative to the increase in risk of intrapartum caesarean delivery for the mother. Greater maternal stature is associated with lower risk of intrapartum caesarean delivery.