Dr Jessica Gehlert
Royal Darwin Hospital 


Title: Relationship between infant birth weight centiles and maternal cardiovascular outcomes at 6 months postpartum
A Lu1; A Henry1,2; L Roberts2,3; G Davis1,2,3
1University of New South Wales, Randwick, NSW, Australia
2Department of Women's and Children's Health, St George Hospital, Kogarah, NSW, Australia
3University of technology Sydney, Ultimo, NSW, Australia

Aims: To examine the correlation between infant birth weight centiles and maternal cardiovascular outcomes at six months postpartum. Additionally, to compare these outcomes, stratified by infant birth weight centile, in mothers who had a hypertensive disorder of pregnancy versus an uncomplicated pregnancy.

Methods: Retrospective cohort study of 238 women and their singleton infants involved in the P4 study at St George Hospital, NSW. Birth weight centiles were calculated using three different methods; the Intergrowth 21-st and Australian national birth weight percentile charts and an Australia-specific customised birth weight calculator obtained from www.gestation.net. Maternal cardiovascular outcomes included mean systolic and diastolic 24-hour ambulatory blood pressures, cholesterol, low-density lipoprotein, high-density lipoprotein and triglyceride levels.

Results: Using simple linear regression, all three methods of centile measurement when compared with cardiovascular outcomes individually, demonstrated a coefficient of determination (R-squared) value of less than 1%. Using linear regression, when maternal cardiovascular outcomes of mothers with a hypertensive disorder of pregnancy were compared to those with an uncomplicated pregnancy, an R-squared value of 13.5% was obtained. When performing the same comparison, stratified by infant birth weight, an R-squared value of 13.6% was obtained. This change was not significant (P > 0.05).

Conclusions: Low R-squared values suggest a limited relationship between centiles and cardiovascular outcomes. Furthermore, as the difference in R-squared value when stratified by infant birth weight centile differed by a minimal amount (0.1%), the impact of centiles as a predictor of cardiovascular outcomes in women at six months postpartum is negligible, whether they had a hypertensive disorder of pregnancy or an uncomplicated pregnancy. Thus, although women with preeclampsia are more likely to have growth-restricted babies, these findings suggest that the baby’s birth weight is unlikely to contribute to predictive modeling of the mother’s cardiovascular risk at six months postpartum.