Reacción a "Reactions: Academic outcomes of IVF-conceived girls and boys do not differ from those conceived naturally"

The study is methodologically of very good quality. The authors have taken into account the confounding factors that we know to be associated with fertility treatment and the possibility of better educational outcomes, such as older maternal age, higher socio-economic status or the educational level of the parents. They have applied various epidemiological analysis techniques to control as much as possible for the variability that is intrinsic in a study of this type, where the data have already been collected and therefore it is not possible to go back and find out more than is available. Overall, the number of children born by assisted reproductive techniques is large, over 11,000, and comparisons with controls who have been born without their parents needing to use the clinic is robust. 

This study confirms and also extends the information we have on the long-term effects of assisted reproductive technologies. It provides information on the school-age development of IVF-born children and confirms that their educational outcomes at 7 and 9 years of age are indistinguishable from those of spontaneous birth. Furthermore, it indicates that there is no difference between the two forms of conception in the likelihood of a child having a severe developmental disorder, at least at this school age.  

As valuable information for health professionals, it should be noted that the cohort of children analysed was born between 2005 and 2014, which means that the results are very relevant to the way we treat infertility today, because in the last 20 years there have been many advances in in vitro fertilisation techniques such as the possibility of culturing embryos for 5-6 days in the laboratory, the possibility of subjecting them to ultra-rapid freezing and the possibility of analysing the genetic content of embryos after "microsurgery" while they are still outside the mother's uterus. There is debate about the impact of these technologies on the peri- and post-natal outcomes of children, so this work contributes greatly to our knowledge and assessment of the long-term risks of assisted reproductive techniques. 

It should always be kept in mind that retrospective studies such as this one cannot control for variables that were not collected at the time the data were generated. However, the statistical techniques used in this case mitigate as much as possible the nature of the limitation.  

There is one curiosity that remains for me, without being a limitation: the authors of the paper do not differentiate between assisted reproduction techniques, most likely due to a lack of detailed information and the difficulty of knowing and taking into account the effect of all the variables that may be involved in an assisted reproduction treatment (the dose of hormones used, the sperm selection technique, the fertilisation technique, how long the in vitro culture of the embryos has been, etc.) on the results of the school tests. There could, for example, be a relationship between the severity of the infertility diagnosis, and therefore the use of more intrusive techniques, and some of the results observed.