One interesting recent publication, that I think may describe a phenomenon in medicine that has not previously been described, is from the NICHD network. This publication noted that there is a great deal of variation in outcomes, specifically survival without major morbidity, among NICUs in the network (Smith PB, Ambalavanan N, Li L, Cotten CM, Laughon M, Walsh MC, Das A, Bell EF, Carlo WA, Stoll BJ et al: Approach to Infants Born at 22 to 24 Weeks’ Gestation: Relationship to Outcomes of More-Mature Infants. Pediatrics 2012.
http://pediatrics.aappublications.org/content/129/6/e1508.long). As others have previously noted, the variation between units is bigger than the effect size of almost any recent neonatal innovation, nitric oxide or surfactant for example.

What this publication did was to compare the outcomes of different NICUS for babies which are all treated actively in all the units, that is babies of 25 weeks gestation and higher. They noted the above mentioned differences. They then examined the ways in which more immature (less than 25 weeks) infants were treated. What they noted were major differences in performance of cesarean sections at 22, 23 or 24 weeks, provision of antenatal steroids and active resuscitation in the delivery room. What they showed was that centers which were more active at 22 to 24 weeks gestation, had better survival without morbidity among the more mature infants, than centers that were less active with the extremely immature babies.

There are a few possible explanations: it could be that centers that were more active attracted lower risk mothers and babies; it could be that, as the mother and fetus progress from 23 to 26 weeks gestation, an active center has a more positive and active attitude all along the spectrum; it could be that being more active with the most difficult babies makes you better at dealing with babies who have fewer acute problems; it could be that centers that are less active at 22 to 24 weeks are more likely to withdraw care from more mature babies (most of the difference was in death, not other complications). I think from looking at the data that the latter seems less likely, but as the mode of death was not reported we can’t be sure.

My own bias from doing this job for many years is that, as you try harder at 23 weeks, you get much better at looking after 25 week infants. That may not be true, but it is consistent with my experience, and I am not sure if it has ever been shown in other domains of medicine. It makes sense that if you are prepared to operate on the most complicated neonatal heat diseases you will have better results with the more straight forward ones, if you try hardest to salvage severe trauma victims, the more moderately injured ones will be easier to save.

Does anyone know if there are data in other fields that are consistent with this guess? My gut feeling is that such data exist, but I don’t know about them.