RESUMO
<p><b>OBJECTIVE</b>To analyze the incidence of low birth weight and identify the influencing factors in China in 2006.</p><p><b>METHODS</b>The national survey was performed by stratified random cluster sampling method in 43 cities and counties in 14 provinces. The subjects were all live neonates during May to October in 2006. Their body weight was measured according to the standardization conducted by the national research team, while the information of all infants was investigated by questionnaires. Non-conditional logistic regression was used to analyze the influencing factors.</p><p><b>RESULTS</b>Among 18 554 infants investigated, the incidence of low birth weight was 4.6% in 2006 in China, being 3.2%, 4.4%, and 6.3% in eastern middle and western areas respectively. The incidence of low birth weight were 3.9% in urban and 4.8% in rural. The results of logistic regression analysis suggested that maternal education (OR = 1.48; 95% CI: 1.181 approximately 1.861), body mass index (BMI) before pregnancy (OR = 1.52; 95% CI: 1.229 - 1.876), body weight gain in gestation period (OR = 1.57; 95% CI: 1.246 - 1.965), gestational weeks (OR = 20.16; 95% CI: 15.456 - 26.297), multiple birth (OR = 12.11; 95% CI: 9.229 - 15.893), gestation syndrome, and nutrition instruction (OR = 0.66; 95% CI: 0.550 - 0.798) were associated with low birth weight significantly.</p><p><b>CONCLUSION</b>The main factors resulting in low birth weight in neonates are maternal education, BMI before pregnancy, body weight gain in gestation period, pregnancy age, multiple birth, gestation syndrome, and nutrition instruction.</p>