Posted as a second answer, because it expands significantly on my original answer in the direction that OP's question was directed.
The Hegemon’s Spacer Pediatric Institute
Inaugural Report regarding the causes of high childhood mortaility in spacer families.
Attempts to control the spacer birth rate through legislation and penalties have failed due to a lack of leverage. Very simply, the productivity cost of enforcing birth controls on our space colonies outweighs the cost of turning a blind eye. Even if it did not, the enforcers that we send, within a very few years, adopt spacer customs and attitudes and stop trying to enforce the regulations.
The result is that spacers have both large families and high childhood mortality rates that are considered unacceptable by terrestrial standards.
This is the first study of many attempting to address these issues. In this study we isolate the root causes of higher childhood mortality rates and identify some of the factors and practices that can mitigate those effects.
Unfortunately, most of the issues identified are, quite literally, forces of nature. As such they are largely immune to any sort of regulation. Regulations and best practices to address these issues have been implemented and are subject to regular review, but those have limited effects. While the Hegemony has extensive resources, even those are inadequate to address the issues that are beyond the ability of the spacer parents to address locally.
As prior reports have discussed, the cost and hazard of lifting workers from Earth to orbit, Luna, orMars, it makes it attractive from a cost perspective to raise and educate the next generation of workers in space, in spite of the initial burden.
Fortunately, space is still as much an experimental as it is an industrial endeavor, so there are complete medical records both cross-sectional and longitudinal, for research.
Space is dangerous, and all of the technology we have brought to bear only mitigates its danger without alleviating it. Nowhere is it more publicly visible than in the child mortality rate.
There are a number of hazards associated with space, which are well documented since the early days of space travel. Children are more susceptible to many of those than adults.
Spacers are not a homogenous group, from either a medical or cultural perspective. For the purposes of this report, we will use “spacers” in the common parlance, meaning anyone whose primary residence is not on Earth. From a medical perspective, there are currently three distinct groups with different health issues.
The traditional “spacer” lives in zero or microgravity, typically in orbital or asteroid mining facilities. They call themselves “orbitals”, a nomenclature that we will continue to use in this report.
Self styled “lunars” live on the surface of earth’s moon in 1/6th gravity.
Self-styled “martians” live on the surface of Mars, in 1/3rd gravity.
The normal health issues associated with space travel (see https://earthsky.org/space/human-health-dangers-mars-travel) are :
Space sickness - equilibrium and spatial awareness being off leads to more accidents. Unusually, orbital children seem to be less susceptible to this particular issue than others. While they are susceptible to vertigo due to sudden inertial changes, such as going from 0G to centrifugally supplied “gravity” and back. It appears to be similar to the degree of vertigo that terrestrial bound children experience on a rollercoaster, with about the same degree of individual variances. Lunar and martian children do not differ appreciably from earthborn children in this respect.
Mental stress - living in a tin can in close quarters with everyone else is mentally stressful. Spacer quarters are very small, and families are in close contact with each other 24 hours per day. This leads to high rates of domestic issues, with no way to protect the children from exposure to those issues. Some children thrive under these conditions, while others develop serious mental health issues. Initially, we expected to see higher rates of physical abuse, but the in very public nature of the confined quarters, the few documented episodes were “self correcting”. That is, the perpetrator was duly restrained by neighbors and the situation was resolved. There is a suspicious confluence of reported incidents preceding lethal mining accidents, but insufficient evidence to prosecute.
Weaker muscles - Muscles not only generate mobility, but they protect the body from injury. Orbital children are the least affected by this due to ready access to centrifugal hubs and a daily regimen incorporating not less than two hours per day of weight bearing at 1G. Lunar children are the most affected, since it is technically difficult and incredibly expensive to engineer and operate a structure to provide 1G for prolonged exercise on the surface of a planet. Martian children experience issues in the mid range. Unlike lunar children, Martian children have sufficient bone density that power lifting has become a popular sport.
Eye problems - particulate contaminants in the spacecraft atmosphere often get lodged in the eyes. Lunar and martian children are no more susceptible to this than terrestrial children. However, orbitals have to deal with this on a continuous basis. As in the early days of space travel, adults have adopted the practice of wearing goggles all the time. Orbitals fit their children with safety goggles from birth, often improvising them from materials at hand.
Coughs and colds - the lungs and sinuses do not clear properly in microgravity, so even minor illnesses are serious health concerns. However, we are starting to discover that certain "illnesses" seem to be necessary for ideal growth and development. Again, counter to intuition, lunar children are most susceptible to these issues, although orbitals are a close second. Even though orbitals have regular access to 1G environments, it is not perpetual so relief is temporary and intermittent. Fortunately, in the most serious cases, there is a certain degree of informal tolerance for children with illnesses in the 1G environments beyond the normal routine.
Medical emergencies - Orbital children are most susceptible to issues due to medical emergencies. Normal childhood roughhousing in zero G is frequently a cause of traumatic injury. Broken bones, concussions, and internal injuries are common. While 0G offers relief from some issues in handling trauma, it creates its own issues, for which orbital doctors have yet to establish viable procedures. If the injuries are not too severe, the patient can be moved, with less trauma than on Earth, to a medical facility in the 1G section of the installation. However, some first response techniques such as CPR and splinting bones, are not feasible in 0G environments. The result is that some injuries that would be readily treated on Earth are fatal in orbit, but others that would be probably fatal on Earth are treatable in orbit.
In addition to the basic list experienced by our adult workers, children experience these specific additional issues:
low bone density - Bone density is driven by peizo-electric reaction to mechanical stress - calcium is laid down in a pattern corresponding to the electric fields generated when the bone is stressed. In microgravity, the bones are not stressed so they don't increase in density normally. What would be minor accidents to an earth bound child can be life threatening some spacer children.
Due to the daily regimen of 2 hours of weight bearing exercise at 1G, orbital children are least afflicted with this particular issue, followed by martians and then lunars.
Lunar bone density is so low that virtually every lunar child could be considered a victim of Osteogenesis Imperfecta. Quite literally, a terrestrial child could accidentally crush a lunar child of the same or even larger size to death. Their bones are literally so fragile that they cannot engage in the kinds of activities that might strengthen them.
In contrast, Martians bones are sufficiently dense that the sport of powerlifting has become popular, which helps to encourage higher bone density.
Radiation exposure - In just one week, orbital children are exposed to the equivalent of one year's exposure on the ground. (see http://www.esa.int/Our_Activities/Human_Spaceflight/Lessons_online/Radiation_and_life). This leads to high rates of childhood cancer and radiation related illnesses.
Radiation shielding has been a target of intense study for the past century, with the major advances being the recognition that there is no such thing as generic “radiation”. Even today, every type of mission is evaluated separately for its particular radiation hazards. Some radiation hazards require heavy metal (lead) protection, while others are better served by a thin sheet of common polyethylene. There is no single “one size fits all” solution that is feasible from both an engineering and economic perspective.
Lunars and martians can be well protected by the simple expedient of constructing their facilities to have a one foot thickness of regolith (rock or brick) outside of the pressure seal. Since children rarely have reason to leave the shelter of the facilities, radiation exposure can be mitigated by simply making it inconvenient for children to leave the facility.
Orbitals, on the other hand, face entirely different sets of constraints, both because of the design of their facilities and the types of radiation they encounter most frequently, which is a function of which orbit they are in.
Facilities that are exposed to hard x-rays and electromagnetic radiation are best served by “just enough” lead shielding to block the radiation, but not enough to cause more harmful secondary radiation. Facilities exposed primarily to high energy particles are best served by a simple plastic liner, replaced periodically in accordance with the manufacturers recommendations.
During solar events (CME’s, periods of heavy sunspot activity, etc), the “designed per mission” shielding may be either insufficient or of the wrong sort for the event. With adult crews, this is a risk that people are willing to accept. Lunars and martians can simply burrow deeper under the regolith for a few hours or even days while the event plays out. Orbitals, on the other hand, have no such luxury. Choosing the incorrect radiation shielding not only provides insufficient protection, but can also exacerbate the radiation issues.
Nutrition - hydroponics and pills simply can't make up for old fashioned dirt farming, especially for the micro-nutrients required for normal growth and development.
Hydroponics and aeroponics are both well established modes of farming, even terrestrially. While they can sometimes outperform dirt based farming, crop failures tend to be spectacular and unpredictable. In general, plants are better adapted to soils than exposed root methods of farming. In addition to providing nutrients and support, the soil acts as a buffer against contamination with metabolic wastes.
Lunar and Martian facilities have been working for decades to treat the native regolith to create a viable soil. Unfortunately, when exposed to water, both regoliths tend to release high (for human consumption purposes) concentrations of perchlorates (essentially household bleach). Early in the 21st century humanity had worked out treatments that permitted potatoes to be grown in analog martian soil. There is a long way between growing potatoes and growing edible potatoes. The cotton and textile plants are usable, but the edible foods are still lagging.
Orbital facilities depend entirely on aeroponics, because the cost of lifting enough water for a hydroponic system into orbit is so high, and the cost of lifting soil (or soil analogs) is similarly high. In an aeroponic system, we need to provide all of the trace elements required for healthy growth.
While purely vegan diets have been known for centuries on Earth, in practice many of those diets were dependent on the accidental ingestion of insects with vegetable matter for essential amino acids. This is why, in developed countries, it is difficult and expensive to raise healthy children on a purely vegan diet.
Lunar and Martian facilities have been designed for fish and animal husbandry, but orbital facilities cannot provide their own animal proteins. In orbital facilities, animal proteins imported from lunar or martian sources are a luxury item that is available only to those who can afford them.
Accidents - imagine the first time your two year old discovers that there's a switch he can flip in the airlock chamber, that he knows he's not supposed to go into (and have you ever tried to keep a 2 year old out of a place he wanted to get into seriously?)
Space borne facilities were not constructed with small children in mind, and as anyone who has had small children knows, there is no such thing as childproof. Toddlers are the ultimate problem solvers - if there are two ways to get into something you want to keep them out of, and you block them both, they will find the third way you never anticipated.
All spacer facilities have multiple redundant safety systems in place for critical functions. Nevertheless, there is a remote possibility that a spacer child could gain access to and mis-operate some critical function and cause issues.
More interesting are the injuries attributed to normal rough play - football or its equivalents for example.
Orbital children have high rates of impact injuries - their daily regime of 1G weight bearing means that their musculature strength approaches the low end of normal for terrestrials, with the skeletal strength to match. When playing sports such as football or tag in 0G, they will launch themselves at high speed, without regard for the consequences of impact. In the tight confines of orbital facilities, the consequences are predictable and occasionally tragic.
Lunar children have high rates of crushing injuries. In normal childhood play, they sustain an impact that would not even be noticed by a terrestrial child, which results in a bone being pulverized. When the skull is the point of impact, the results are often deadly. While some families opt to make their children wear helmets all the time, others find the high rate of hard to treat skin infections that go with the continuous use of the helmets is prohibitive. Since the children will remove their helmets at every opportunity, the benefit of helmets is questionable.
While under normal circumstances the martian gravity alone is insufficient to encourage proper skeletal growth, the popularity of the sport of powerlifting on Mars is in no small part responsible for the better outcomes for martian children versus their lunar counterparts. The martian children start with twice the bone density of their lunar counterparts, and with good training and supervision, quickly approach the bone density that orbital children enjoy with their 2 hours per day of 1G.
Toxic exposure to airborne chemicals and space dust
In the recycled air of the space environment, toxins that are innocuous on earth can build up quickly to dangerous levels. A prime example is the prohibition against the use of alcohol hand wipes in spacer greenhouses. The vapors from alcohol wipes, which are innocuous and readily absorbed on earth, become quickly toxic and can wipe out an entire season’s food crops.
Certain contaminants are ubiquitous to industrial facilities everywhere. Spacer facilities are much more meticulous about scrubbing those contaminants than terrestrial facilities have ever been, nevertheless they do sometimes seep into the systems and wreak havoc.
Lunar and martian facilities, in particular, are subject to contamination with local regolith dust. In contact with water, the lunar and martian surface minerals release perchlorates is concentrations sufficient to make humans ill. Children’s lungs, which are still developing, are more susceptible (https://en.wikipedia.org/wiki/Adverse_health_effects_from_lunar_dust_exposure).
It is easy to presume that orbital facilities are immune to regolith contamination, but that is dependent on the precise nature of the orbital facility. Asteroid miners will have to deal with regolith dust contamination whose composition varies from virtually inert to highly reactive. Comet miners will have to deal with ammonia and other organic compounds, in addition to the probable but not guaranteed presence of perchlorates.