Risk factors for small for gestational age infants

There are many established risk factors for babies who are small for gestational age (SGA) by population birth weight centiles (usually defined as <10th centile). The confirmed maternal risk factors include short stature, low weight, Indian or Asian ethnicity, nulliparity, mother born SGA, cigarette smoking and cocaine use. Maternal medical history of: chronic hypertension, renal disease, anti-phospholipid syndrome and malaria are associated with increased SGA. Risk factors developing in pregnancy include heavy bleeding in early pregnancy, placental abruption, pre-eclampsia and gestational hypertension.

A short or very long inter-pregnancy interval, previous SGA infant or previous stillbirth are also risk factors. Paternal factors including changed paternity, short stature and father born SGA also contribute.

Factors associated with reduced risk of SGA or increased birth weight include high maternal milk consumption and high intakes of green leafy vegetables and fruit.

Future studies need to investigate risk factors for babies SGA by customised centiles as these babies have greater morbidity and mortality than babies defined as SGA by population centiles.