Omphalocele is a congenital malformation that involves protrusion of abdominal contents into the umbilicus. Though omphalocele may present as a manifestation of several chromosomal and Mendelian syndromes, the etiology for nonsyndromic omphalocele is unknown. The present study sought to estimate the birth prevalence of nonsyndromic omphalocele in offspring of women residing in Texas from 1999 to 2004, and to describe prevalence as a function of parental and infant demographic characteristics. Data on 325 cases with nonsyndromic omphalocele and 2,208,758 live births delivered during 1999-2004 were obtained from the Texas Birth Defects Registry. These data were used to estimate omphalocele birth prevalence and obtain both crude and adjusted prevalence ratios for the association of nonsyndromic omphalocele with parental and infant demographic characteristics. Nonsyndromic omphaloceles were significantly more common among the offspring of women without previous live births (adjusted prevalence ratio: 1.80, 95% CI: 1.41-2.30), compared to the offspring of women with previous live births. The prevalence of nonsyndromic omphalocele was also increased among women aged 25-29 (adjusted prevalence ratio: 1.68, 95% CI: 1.12-2.50) and women aged 40 and older (adjusted prevalence ratio: 4.83, 95% CI: 2.63-8.86) compared to the offspring of women age <20, and in infants of multiple gestation pregnancies compared to singleton infants (adjusted prevalence ratio: 2.03, 95% CI: 1.22-3.37). In addition, among Hispanic women, the prevalence of nonsyndromic omphalocele was higher in the offspring of those born in the U.S. as compared to those born elsewhere (adjusted prevalence ratio: 1.50, 95% CI: 1.12-2.00). These findings augment the existing omphalocele literature.