Prenatal, birth, and postnatal mediators of maternal education level and childhood obesity at five years.

Objective: To establish which prenatal, birth, and postnatal characteristics mediate the association between maternal educational level and having a child with obesity at five years.

Study Design: This is a sub analysis of a longitudinal study nested in the BMInForma (Bambini Molto In Forma) program. BMInForma is an ongoing public health multilevel intervention started in 2013 to prevent childhood obesity.

Methods: A cohort of 4835 children born from 1.7.2010 to 31.12.2011 and who received well-health visit at three and five years of age in Reggio Emilia, Italy were included in the study. Maternal and child anthropometric and lifestyle data were linked with routinely collected birth data. A series of simple and multiple mediation analyses were performed.

Results: There were 232 (4.8 %) children with obesity at five year visit. Low maternal educational level was significantly associated with children's obesity at 5 years of age (Odds ratio for the total effect 1.8, 95 %CI 1.4 - 2.5), and with almost all prenatal, birth, postnatal and 3-years-old behaviors. Pre-pregnancy overweight and obesity (OW/OB) and hours in front of TV at three years were two significant mediators that explained 32 % of the total effect of maternal educational level on children with obesity at five years of age (Odds ratio for the indirect effect 1.17, 95 %CI 1.10 - 1.24). Nine percent of this effect was evinced through LGA and gestational diabetes (Odds ratio for the indirect effect 1.07, 95 %CI 1.01 - 1.13).

Conclusions: Pre-pregnancy OW/OB was the most important mediator of the effect of maternal educational level on childhood obesity at five years. Interventions are needed to increase awareness of unhealthy behaviors in early pregnancy.