Abstract Objective: The aim of this study was a comparison of the outcomes of intrauterine myelomeningocele (MMC) repairs (IUMR) in type II Chiari malformation (II CM) fetuses with clinical data of newborns and infants operated on postnatally. Methods: The study group (SG) comprised 46 pregnant women whose type II CM children underwent IUMR, while 47 pregnant women whose type II CM children were operated on postnatally constituted the control group (CG). A total of 24 SG and 20 CG patients reached the endpoint of the study. Results: High incidence of prelabor rupture of membranes (24 (52.2%), CI: 3.74 (1.69-8.26) (p < 0.001) was noted in the group of prenatal surgeries as compared to controls. The need for ventriculoperitoneal shunt implantation was statistically significantly lower (p < 0.008) in the group of children after IUMR as compared to controls (5 (27.8%) and 16 (80%), respectively, CI: 0.35 (0.16-0.75). None of the postnatally treated CG children can walk without adaptive equipment. In contrast, two children from the SG (2 (11.1%) CI: 1.86 (1.00-3.48) p < 0.05) are able to walk independently. Conclusions: Prenatal MMC closure significantly lowers further adverse evolution of the II CM. Further studies are needed, especially on preventive measures for preterm labor and iatrogenic preterm prelabor rupture of membranes (iPPRM) in the postoperative course of IUMR.