If a child is conceived through sexual assault, the rules vary widely on the parental rights of the attacker.

To learn more about parental rights laws for rapists throughout the United States, watch “This is Life with Lisa Ling” Sunday, November 20 at 10 p.m. ET.

CNN  — 

It’s an almost unimaginable scenario: a victim of rape being forced to face her attacker over custody rights for a child conceived during an assault.

“Almost” is the key word, because it’s a situation that can easily happen in states across the United States. The shorthand for this occurrence is often referred to as “parental rights for rapists,” a phrase that’s mind-boggling but accurate in its representation of the issue.

Without any legislation stopping a sexual assailant from claiming parental rights of a child, individuals are free and clear to pursue custody or visitation rights of their biological offspring.

The big picture of how parental rights for rapists are treated across the US

Seven states don’t have any laws preventing a rapist from claiming parental rights, but that’s not to say that these states are oblivious to the issue. Maryland, for one, has been working for years to pass a law that would allow a rape victim to terminate her attacker’s parental rights.

Forty-three other states and the District of Columbia have legislation that offers at least some protection to prevent rape victims from facing their attackers over parental rights; eight of those laws were just adopted in 2016.

But these legislative protections vary greatly. In 20 states and D.C., a rape conviction is required before a victim can request termination of parental rights.

For advocates, this is a problematic barrier, since the majority of sexual assaults don’t even make it to prosecution, according to the Bureau of Justice Statistics (PDF).

Between 2005 and 2010, just 36% of the nearly 300,000 annual average rape or sexual assault victimizations were reported to police, the bureau reports. Even when you look at both reported and unreported rapes during that time period, roughly 12% of victimizations resulted in arrests.

That means in nearly half the states that have legislation meant to prevent rapists from claiming parental rights, a victim is still vulnerable to having to face her attacker if there wasn’t a conviction in her case – and that’s if she reported it and if it was prosecuted.

There are also exceptions, called “carve-outs,” to consider. Some states may not apply these parental rights laws if, say, the person convicted of sexual assault is the spouse of the victim at the time of the attack or if they were cohabiting after the assault.

In Indiana, timing is everything: The victim must petition to have her assailant’s parental rights terminated less than three months after the child’s birth unless the victim is younger than 18. In Nebraska, the law applies only to sexual assault in the first degree.

Use the menu below to see the general rules in your state.

CNN’s Tal Yellin contributed to this report.