Comparison of Risk Factors for Small-for-Gestational-Age and Preterm in a Portuguese Cohort of Newborns

Objective: To identify risk factors for small-for-gestational-age and preterm in a Portuguese cohort of newborns. Study design: Socio-demographic, anthropometric, behavioural and obstetrical characteristics were evaluated in 4.193 women consecutively delivered. Term small-for-gestational-age (n = 342) and non-small-for-gestational-age preterm (n = 148) were compared to non-small-for-gestational-age term births (n = 3538). Adjusted odds ratios and etiologic fractions were calculated. Results: Low height, low weight when entering pregnancy and low weight gain were significantly associated with small-for-gestational-age, but not preterm. These were the factors with the highest etiologic fraction for small-for-gestational-age. An increased risk of small-for-gestational-age was found for women who smoked during pregnancy (OR = 2.39; 95% CI: 1.66–3.46) and began antenatal care after pregnancy first trimester (OR = 1.86; 95% CI: 1.32–2.62). Previous abortion was associated with small-for-gestational-age (OR = 1.72; 95% CI: 1.16–2.55) and previous preterm with preterm (OR = 3.20; 95% CI: 1.26–8.14). Conclusions: Low anthropometrics, smoking and late antenatal care were risk factors for small-for-gestational-age, but not preterm. Maternal anthropometrics were the factors with the highest impact on small-for-gestational-age. No factor showed a great contribution to preterm birth.