The 55 studies that met the inclusion criteria were good science and those ones showed no difference between naturally conceived and surrogate children’s well being at age 10.
The 55 included studies were rated on the quality of their evidence as part of the review - only 1 was high quality, 16 were moderate, 13 were low. The evidence for each aspect of the paper is given a grade and there are several sections which are classed as low or very low quality as a whole. The exclusion criteria was separate and wasn't to do with evidence quality so much as being the wrong type of study, the wrong language/translations from other languages, or double publications etc.
As for following the children until age 10, it's a start, but I'd be more interested in longer term outcomes that go well into adulthood, or at the very least into the teen years as that would give a better indication of emotional development. It's also worth noting that while at age 10 adjustment issues of surrogate children might have disappeared, they were more prevalent at age 7 and only declined after that. The larger study in Brazil showed evidence of speech delay, growth and motor development in early years. Obviously all to be considered with the caveats of not necessarily being great quality data, but if we're operating on the premise that we need to follow the science available, it still relevant that there is an impact on children even if it declines with age.
For one, the primary beneficiaries of surrogacy are fellow women who have infertile wombs and there is no other way to have a child with a biological link to themselves
Which is irrelevant in the context of gay male couples (no women benefitting there) or women that are following traditional surrogacy or using a third party egg donor (no genetic link to themselves).
In other cases it isn't just the woman, it's the couple as a unit that benefits. I can see your point where the commissioning mother is the egg donor, and I get that it's not a clear cut patriarchal oppression like prostitution due to the balance of the sexes, but when money is added into it there is still a discrepancy in the power dynamic between the commissioning couple and the surrogate mother, which makes me uncomfortable. The 'I'm paying, therefore I have control' mentality isn't uncommon in any walk of life. I don't think the fact that there are some women genuinely happy to become surrogate mothers (which there inevitably are) is enough to convince me that on the whole there is no risk of exploitation, and given that the victim of that exploitation will always be female, it’s a problem for me.
I don’t think it’s accurate to say it’s primarily altruism that is the primary motivator either. In the US and other countries commercial surrogacy is allowed which almost certainly means in some instances money is the primary driver (although people aren’t that likely to admit it - when everyone is gushing over how selfless you are, you aren’t going to turn around and say ‘oh actually it’s because they’re paying me a significant amount’, the average person would just take the praise). Many commercial surrogate mothers probably do believe altruism is their driving motive and that’s absolutely their prerogative and I wouldn’t question someone that said it to me, but I’d be interested at how much the numbers drop if commercial surrogacy was outlawed in the US and only very strict and limited expenses were permitted. It would be a much better indication of how altruistic the surrogacy industry there actually is, rather than self-reporting. I also haven’t seen anything which considers the very real risk of ‘independent’ surrogacies that are able to occur. All the commissioning family needs to do is find a willing woman (whether because she is being genuinely altruistic, or simply needing the money), provide the sperm, and fund the medical costs and legal fees for terminating the mother’s legal rights and adopting the baby independently rather than going through an agency (all possible in the US). I’d be surprised if this doesn’t happen (not necessarily in considerable numbers though) and its unlikely it would be classed in any official numbers or studies, plus its a relatively simple way of avoiding ethical restrictions and finding a cheaper local surrogate mother rather than going abroad. Obviously that’s just speculation but there’s no way of regulating that type of scenario to ensure poorer women aren’t being exploited.
Fundamentally it’s still an industry based on women putting their health, comfort, and personhood at risk for the benefit of (an often more privileged, at least financially) third party, in exchange for money. And that’s without considering the impact on the child which adds another layer of ethical complication. It might not be exactly the same as prostitution but I don’t think the parallels can be so easily dismissed.
If commercial surrogacy was banned globally, restrictions were put in place to stop any cross border arrangements, and expenses were properly and very strictly limited so there was no financial benefit to the surrogate mother involved, and it was guaranteed there was no risk of societal pressure or coercion (ie she is truly doing it for purely altruistic reasons for family or friends), I could probably agree with it from the perspective of its impact on women as a matter of policy, but I just don’t see it happening.
Either way, this has been an interesting thread so far!