Abstract: Compositions and methods for fetal or in utero delivery of active agents are provided. The compositions are most typically administered intravenously via the vitelline vein, umbilical vein, or directly into the amniotic cavity of a pregnant mother. Growth factors can be delivered to correct structural defects. Gene editing can be carried out utilizing a gene editing composition such as triplex-forming molecules, CRISPR, zinc finger nucleases, TALENS, or others. The methods can include administration of a gene modification potentiating agent such as stem cell factor (SCF), a CHK1 or ATR inhibitor, or a combination thereof. A particularly preferred gene editing composition is triplex-forming peptide nucleic acids (PNAs) substituted at the ? position for increased DNA binding affinity. Polymeric particle compositions for extracellular and intracellular delivery of the active agents are also provided.