Nearly half a century ago, just over a dozen friend-of-the-court briefs took positions for and against a right to abortion in the case Roe v. Wade. When the U.S. Supreme Court reviews a new and direct challenge to that landmark ruling next term, the justices likely will face at least six times that number, if not more, as parties seek to sway the outcome.

Much has changed in the abortion rights landscape since 1973, when a 7-2 Supreme Court recognized a woman’s constitutional right to abortion. At the Supreme Court, friend-of-the-court, or amicus, briefs have changed as well. They have ballooned in number, broadened in substance and diversified in the parties filing. The court headed by Chief Justice John Roberts Jr. exemplifies all three trends.