Introduction Infants born small for gestational age (SGA) are at higher risk for morbidity. This analysis explored whether increased risk is attributable to SGA or its causes.

Methods A population-based cohort (n=2357) was recruited at 10–22 weeks gestation. We collected prenatal data by questionnaire, perinatal data from hospital records, and follow-up data by telephone survey 2–4 years later. Outcomes included neonatal admission to special care nursery (NASC), neonatal Apgar score <7 at 1 min (Apgar1) and, hospital admission (HA) during the 12 months preceding the follow-up interview. Analyses included multivariable logistic regression.

Results Preeclampsia had statistically significant multivariable associations with NASC and Apgar1; OR's (95% CI's) were 2.0 (1.0 to 5.0) and 2.4 (95% CI 1.3 to 4.3), respectively. Apgar1 was also associated with young maternal age and obesity. In secondary analysis restricted to term deliveries, threatened preterm labour (TPL) had OR's of 3.9 (1.6, 9.3) and 2.2 (1.2, 4.2), respectively, for NASC and Apgar1. TPL displaced preeclampsia from the model indicating correlation. Since recent literature suggests that preeclampsia, TPL, and SGA have common aetiologies, we combined these into a single construct, Placenta Associated Syndromes (PAS)(Alilu et al 2010). The OR's of PAS with NSC and Apgar1 were 3.9 (1.6, 9.3) and 2.2 (1.2, 4.2), respectively. HA had multivariable associations with preeclampsia and maternal depression (CES-D>24) with OR's of 2.6 (1.1, 6.1) and 2.9 (1.3, 6.4). SGA was not independently associated with outcomes studied.

Conclusion We conclude that SGA is a marker for placental dysfunction, which is the true risk factor for the outcomes studied.