[Associations between birth outcomes with blood pressure level and risk of high blood pressure in childhood].

Objective: To explore the associations between birth outcomes and blood pressure, and study the sex dimorphism of these associations.

Methods: With a multistage cluster random sampling method, 62 168 children were recruited in seven provinces of China in September of 2013, with 32 064 boys and 30 104 girls, median age of 10.74 years and mean birth weight of 3.3 kg, 49 843 single birth(97%), 1339 twin(2.6%), 180 triplet or more(0.4%). Questionnaire investigation and physical examination were conducted in the present study. Weight, height and blood pressure were measured in the physical examination. Demographic characteristics, birth outcomes(including birth weight and number of births), dietary behavior, physical activities were measured by questionnaire. The widely used age-, gender-and height-specific high blood pressure standard developed by American CDC was used for the present study. Multivariate linear and logistic regression analysis were conducted to study the associations between birth outcomes and blood pressure level or high blood pressure(HBP), and also sex dimorphism of these associations was explored.

Results: A total of 5933 children were categorized as having high blood pressure in the 62 168 participants(9.5%). With stratified analyses by birth weight category, only in the low-birth-weight strata birth weight was significantly inversely associated with systolic blood pressure(SBP) and diastolic blood pressure(DBP) with potential covariates adjusted(SBP: b=-1.628, 95%CI-2.571--0.685, P=0.001; DBP: b=-1.463, 95%CI-2.186--0.740, P<0.001). While compared with the non-low birth weight children, low birth weight was not associated with higher risk of HBP(P>0.05). Compared with those boys born as singleton, boys born as one of the twins have a 36.4% higher risk of HBP(OR=1.364, 95%CI 1.049-1.774), while in girls no such significant association was found. Additionally, compared with a term birth, overdue birth and preterm birth was not associated with higher risk of HBP(P>0.05).

Conclusion: Birth weight and singleton or not were associated with childhood blood pressure levels and higher risk of high blood pressure, and some associations were sex specific. Gender differences should be paid attention to in the prevention and control of high blood pressure in children and adolescents in the future, and the prevention and control should be focused on low-birth weight children or twin boys.