There has been a lot of talk about co-bedding twins in the NICU, but relatively little research.
I was involved in an RCT of co-bedding in preterm twins, looking at responses to painful stimuli (67 pars of twins were recruited). We randomized twin pairs who were between 28 weeks and 36 weeks and needed a heelstick to either stay in their separate cots, or be placed touching each other in the same incubator or cot. The primary outcome of the study was the PIPP scores, which were not different (it is very interesting that all the babies received sucrose adn were offered a soother, so the peak PIPP scores only went up to just over 7 in each group, quite a modest elevation), but a secondary outcome analysis showed that the babies in co-bedding settled down faster than the controls, returning to baseline heart rate and saturation levels faster.
Marsha Campell-Yeo, who was the PI for the study, has just published the analysis of the salivary cortisols in the babies, which were slightly lower at baseline in co-bedding (not significant) and which increased in the controls, but not in the co-bedded twins after the painful event. So 20 minutes after the heelstick the levels were significantly lower in the co-bedded twins than the controls.
We were interested during the planning phase to see if the co-twins might get stressed by the procedure (and a bit concerned that it might be an adverse effect of co-bedding), there wasn’t any sign of that happening. The question of the mechanism is interesting; I think that human contact is comforting, re-assuring and pleasurable, certainly hugging my kids is. I don’t know if it really matters whether it is a co-twin or if the same might occur with another random baby from the NICU, but I don’t think we will do the study to find out.