"Often it will be a nursery nurse who comes to the birth but can't stay," she says. And to have successful skin-to-skin that lasts long enough — at least an hour — you need a designated nurse in the room. "The hospitals just don't want to pay the extra money," Moore says.

The Cochrane Collaboration, an international organization that evaluates and reviews medical research, coordinated the review of evidence, which looked at 45 randomized controlled studies of a total of 3,850 women and their newborns from 21 countries.

"Babies are often separated from their mothers at birth," the review notes. "In standard hospital care, newborn infants can be held wrapped or dressed in their mother's arms, placed in open cribs or under warmers. In skin-to-skin contact (SSC), the newborn infant is placed naked on the mother's bare chest at birth or soon afterwards. Immediate SSC means within 10 minutes of birth while early SSC means between 10 minutes and 24 hours after birth. We wanted to know if immediate or early SSC improved breastfeeding for mothers and babies, and improved the transition to the outside world for babies."

It did: Compared with babies and mothers who were separated, those who received skin-to-skin contact immediately after birth were about 24 percent more likely to still be breastfeeding up to four months later. The SSC infants, in turn, were 32 percent more likely to successfully breastfeed on their first try. Other evidence showed that women who got SSC breastfed longer and were more likely to exclusively breastfeed after leaving the hospital — and babies had better heart and lung function.

The earliest studies that Moore and her team looked at were from the 1970s, when the idea of skin-to-skin contact was "really radical," she says, and the norm was to separate mom and baby for 12 to 24 hours.

And that's not to say it doesn't still happen. As part of an expansive 2015 interview series about women's upsetting and traumatic birth stories, "Exposing the Silence," many subject talked about being mysteriously separated from their newborns for long periods of time and never given a straightforward explanation.

"It's been the most traumatizing moment for everyone," Cristen Pascucci, a birth activist with Improving Birth and Birth Monopoly and a co-creator of "Exposing the Silence," told Yahoo at the time. "In one case, a doctor told the mom she'd have her baby back in 20 minutes, and [the other medical staffers] in the room laughed." When the doctor left the room, the others explained that "he always says that" and that, in reality, it would be several hours. One hospital, she added, had a policy of keeping babies away from moms for a full 12 hours.

In addition to preventing, to some extent, healthy hearts and ease with breastfeeding, keeping newborns separated from mothers adds to infant anxiety, a 2011 study found. "We knew that this was stressful, but the current study suggests that this is major physiologic stressor for the infant," John Krystal, MD, editor of Biological Psychiatry, where the study was published, had said of the findings at the time.

One way of counteracting the lack of skin-to-skin in operating rooms, Moore notes, is by letting dads and other co-parents step in. "It's not been studied as much as mother-baby skin-to-skin," she says. But the few researchers who have looked at it have found optimal results.

In the meantime, Moore believes hospitals will eventually need to update their policies as a result of all the findings on SSC. "I think there's going to be more and more consumer demand for skin-to-skin in the operating room," she says.