Mo. Rev. Stat. § 546.800

If, after any female convict shall be sentenced to the punishment of death, the officer having charge of her person shall have reason to suspect that she is pregnant, he shall in like manner summon a jury of six persons, not less than three of whom shall be physicians, and shall give notice thereof to the prosecuting attorney of the county where such criminal proceedings originated, or to the circuit attorney of the city of St. Louis, if such criminal proceedings originated in that city, who shall attend, and the proceedings shall be had as provided.