Natural history of prenatal isolated muscular ventricular septal defects

To evaluate the natural history of isolated muscular ventricular septal (m-VSD) defects during gestation and up to 1 year postnatally, as well as the association with chromosomal anomalies. Between August 2007 and July 2012, 76 fetuses with isolated m-VSDs represented the study population. The following variables were evaluated: site and size of the m-VSDs, presence of chromosomal anomalies, pregnancy outcome, and spontaneous closure rate from diagnosis up to 1 year postnatally. Of the 76 cases with m-VSD, 1 fetus died after birth and 31 cases were lost to follow-up after birth. Thus, a total of 44 fetuses reached their first year of postnatal life, and these cases were available for analysis. Three (6.8%) of 44 defects closed spontaneously in utero, 33 (75%) closed within 1 year, and 8 (18.2%) remained patent. Overall, spontaneous closure occurred more frequently in the apical defects, but no significant difference was found for spontaneous closure between the mid-muscular and apical defects (p>0.05). Also, 83.8% (36 of 44) of defects ≤3 mm closed during gestation or the first year of life. We infer that m-VSDs have a high spontaneous closure rate during the first year of life. Also, small m-VSDs frequently close spontaneously.