There has never been a law that better served its purpose than Laci and Conner's Law.
Whoever engages in conduct that violates any of the provisions of law listed in subsection (b) and thereby causes the death of, or bodily injury (as defined in section 1365) to, a child, who is in utero at the time the conduct takes place, is guilty of a separate offense under this section.
… Except as otherwise provided in this paragraph, the punishment for that separate offense is the same as the punishment provided under Federal law for that conduct had that injury or death occurred to the unborn child's mother.
Consider the evidence: Since the passage of Laci and Conner's Law, inspired by the Scott Peterson trial, there have been no prosecutions for felonious injuries inflicted upon unborn children on federal land.
According to a quick Google/Nexis search, there have been no reported cases of felonious injuries inflicted upon unborn children on federal land.
Therefore, this law is serving its purpose. Simple Justice has much more on the successful deterrent effect that Laci and Conner's Law has exerted upon those who, prior to its passage, sought to feloniously injure unborn children on federal land.