Purity Balls, where a daughter’s worth is determined by the state of her hymen, are currently all the rage among America’s Christian extremists.

Purity Balls are creepy religious ceremonies infused with ritual father-daughter incest where daughters who have just begun menstruating are formally instructed that they “are married to the Lord” and that their father is their “boyfriend.”

It’s like a wedding but with a twist: Young women exchange rings, take vows and enjoy a first dance…with their dads.

At the Ball, which resembles a giant wedding ceremony, girls around the age of 12 wear white gowns and pledge to remain ‘pure’ until their wedding day. The girls symbolically ‘marry’ God, and promise their father they will remain a virgin until they are wed.

(Note the typical, sexist, double standard, common to most, if not all, religious traditions: There is no Purity Ball for a 12 year old boy to ‘entrust’ his virginity to his mother.)

At the ceremony fathers present their daughters with purity rings, which the girls wear to symbolise their commitment to virginity and an intact hymen. The father, as “High Priest” of the household, promises to protect his daughter’s virginity, promising “before God to cover my daughter as her authority and protection in the area of purity.”

To make it all official, the father signs the following contract, witnessed by his daughter:

PURITY COVERING AND COVENANT I ………’s father, choose before God to cover my daughter as her authority and protection in the area of purity. I will be pure in my own life as a man, husband and father. I will be a man of integrity and accountability as I lead, guide and pray over my daughter and my family as the High Priest in my home. This covering will be used by God to influence generations to come.

A profoundly sexist and misogynistic expression of contemporary American Christian culture, Purity Balls degrade young women, promoting the antiquated and morally repugnant notion that girls are property, and that a daughter’s worth is determined by the state of her hymen.

A documentary on Purity Balls premiers on “Nightline Prime,” Saturday, March 22 at 9 p.m. ET.