Problem: We evaluated associations between a length polymorphism in intron 2 of the gene coding for IL-1ra (gene symbol IL1RN) and pregnancy outcome in a population with a high rate of preterm birth.
Method of study: Subjects were pregnant women in Maceio, Brazil and their newborns. DNA was tested for IL1RN genotypes and alleles by gene amplification using primer pairs that spanned the polymorphic region. Every subject completed a detailed questionnaire.
Results: The frequency of allele 2 (IL1RN*2) carriage was elevated in mothers with a spontaneous preterm birth (SPTB) in the current pregnancy (P = 0.02) and also with a prior preterm delivery (P = .01). Both SPTB with intact membranes (P = 0.01) and SPTB preceded by pre-term premature rupture of membranes (P = .03) were associated with ILlRN*2 carriage. A previous fetal demise was more than twice as prevalent in mothers positive for two copies of IL1RN*2.
Conclusion: Maternal carriage of ILlRN*2 increases susceptibility to inflammation-triggered spontaneous pre-term birth.