The research study found that that single mothers are not perceived as less competent or less committed than single childless women, and they are not less likely to be hired or promoted compared to their childless counterparts. As such, they do not suffer the motherhood penalty like married mothers do.

“When a woman is known to be single and when she has children, then in addition to being a caregiver, she's also a breadwinner,” she says. “She now also has to provide for her family and she has no one to fall back on.”

However, single moms don't get the premium either – but then again, neither do single dads. “Single fathers, in addition to being breadwinners, are caregivers to their offspring,” Abromaviciute says. “Likely, this triggers an assumption that they are more focused on their family than a married father might be, which eliminates the fatherhood premium.”

Like earlier research, the UA student also found bias for married parents in her research study, concluding that “marital status operates as a strong status cue that, combined with gender and parenthood status, leads evaluators to make assumptions about one's anticipated performance at work.”

There's a caveat in her research, Abromaviciute says: the fictitious single parents in the study were applying for upper an management position, and people might feel more bias against working-class single moms and dads.

“In real-world situations, single mothers often face structural challenges — lack of social support, lack of education, lack of valuable and relevant workplace experience, as well as limited time for hobbies and interests presented on resumes used in the study,” she says. “So, these findings likely apply for middle-class applicants and employees,” but “we don't know what happens in working-class jobs.”

To remedy the motherhood penalty potentially impacting married moms' pay, some employers are conducting pay audits and standardizing the criteria on which performance reviews are based, according to HR Dive. “Others say employers won't see a change until they give working fathers paid parental leave,” HRDive writes. “Such a move requires more than a policy change, however; it also requires a change in a workplace's cultural mindset, whereby caregiving is no longer perceived as largely the responsibility of women.”

Such a move may ensure compliance with federal nondiscrimination law, too, if an employer offers paid parental leave to women, the publication adds.