Small-for-gestational age and its association with maternal blood glucose, body mass index and stature: a perinatal cohort study among Chinese women

OBJECTIVE To examine whether maternal low blood glucose (BG), low body mass index (BMI) and small stature have a joint effect on the risk of delivery of a small-for-gestational age (SGA) infant. DESIGN Women from a perinatal cohort were followed up from receiving perinatal healthcare to giving birth. SETTING Beichen District, Tianjin, China between June 2011 and October 2012. PARTICIPANTS 1572 women aged 19-39 years with valid values of stature, BMI and BG level at gestational diabetes mellitus screening (gestational weeks 24-28), glucose challenge test <7.8 mmol/L and singleton birth (≥37 weeks' gestation). MAIN OUTCOME MEASURES SGA was defined as birth weight <10th centile for gender separated gestational age of Tianjin singletons. RESULTS 164 neonates (10.4%) were identified as SGA. From multiple logistic regression models, the ORs (95% CI) of delivery of SGA were 0.84 (0.72 to 0.98), 0.61 (0.49 to 0.74) and 0.64 (0.54 to 0.76) for every 1 SD increase in maternal BG, BMI and stature, respectively. When dichotomises, maternal BG (<6.0 vs ≥6.0 mmol/L), BMI (<24 vs ≥24 kg/m(2)) and stature (<160.0 vs ≥160.0 cm), those with BG, BMI and stature all in the lower categories had ∼8 times higher odds of delivering an SGA neonate (OR (95% CI) 8.01 (3.78 to 16.96)) relative to the reference that had BG, BMI and stature all in the high categories. The odds for an SGA delivery among women who had any 2 variables in the lower categories were ∼2-4 times higher. CONCLUSIONS Low maternal BG is associated with an increased risk of having an SGA infant. The risk of SGA is significantly increased when the mother is also short and has a low BMI. This may be a useful clinical tool to identify women at higher risk for having an SGA infant at delivery.