In some abusive relationships, men may use strategies to force women to become pregnant, including sabotaging their birth control, researchers say.
Nearly 20 percent of women at family clinics across northern California reported that their partner tried to coerce them into having a child, sometimes using methods such as poking holes in condoms or flushing birth control pills down the toilet, Dr. Elizabeth Miller of the University of California Davis and colleagues reported online in the journal Contraception.
"It was stunning to have this many women seeking reproductive health services saying, 'this has happened to me,'" lead study author Miller said. She added that the reasons men would want their partners to bear children vary "from things like wanting to leave a legacy, to a straightforward desire for attachment, to having absolute control over her body... There are all of these elements to it."
Dr. Aisha Mays, director of the Teen and Young Adult Clinic at San Francisco General Hospital, said pregnancy coercion is a growing problem that has been around for "quite some time" but is just now being recognized as a major health issue.
"It's about power and control," said Mays, who was not involved in the study. "It's another way of saying, 'This girl's taken; this girl's mine.'"
Mays said she has seen cases in which a young mother who has a child by another partner has been forced by her new boyfriend to have another baby with him.
It's also a way for males to make their partners more dependent on them, according to Amy Bonomi of Ohio State University.
"Women in abusive relationships are sometimes forced to bear children as a means to keep them dependent on their partner and sometimes as a means to justify additional -- and sometimes more severe -- abuse," Bonomi said.
Miller said pregnancy coercion often consists of verbal threats, demands, and physical violence to pressure women to become pregnant. Alternatively, some men sabotage birth control by flushing pills down the toilet, breaking condoms, or removing contraceptive rings and patches.
Indeed, previous studies have found an association between partner violence and unintended pregnancy, and new research suggests that a man's attempts to control a woman's reproductive choices may play a role in the association.
"We've known for a long time in the domestic violence world that partner violence and unintended pregnancy are connected; we just haven't understood the mechanisms," Miller said.
To investigate, the researchers conducted a survey of women ages 16 to 29 who sought care at family planning clinics in northern California.
More than half of the women surveyed – 53 percent -- reported physical or sexual partner violence. Miller noted that women at family planning clinics tend to have higher rates of abuse than the general population.
Among all the women, 19 percent reported pregnancy coercion, and 15 percent reported birth control sabotage.
More than a third of women – 35 percent -- who reported either form of what researchers call "reproductive control" also reported partner violence.
Altogether, the effect of both partner violence and reproductive control nearly doubled a woman's odds of unintended pregnancy.