In order to study the long-term effects of balloon mitral valvoplasty (BMV) on childhood development, we followed up closely 20 mothers with severe mitral stenosis who were treated with BMV during pregnancy. Their offspring aged 63 ± 39 (range 6–98) months were also regularly assessed using standard developmental charts and relevant laboratory tests. They were all found to have maintained normal growth, development, and speech for their appropriate ages. Developmental milestones were normal for their ages and comparable with those of their siblings. The laboratory tests revealed no abnormalities. Two losses occurred during the early course of follow-up, at the ages of 4 and 37 weeks, respectively. One of the pregnant patients suffered a stillbirth.