Multivariable regression analysis revealed that the negative effect of the SP-A1 6A4 and SP-A2 1A5 haplotypes was preserved when adjusting for known risk or protective factors, such as male gender, smaller gestational age, smaller size (weight) for gestational age, complications of pregnancy and administration of antenatal corticosteroids, with the carriers of the 6A4 and 1A5 haplotypes having a 4- and 5-fold higher probability for RDS, respectively (Table 4). This evidence concerns the gene SFTPA1 and newborn respiratory distress syndrome.