Yolanda Cabello
Independent clinical embryologist and consultant in assisted reproduction and lecturer on the Master's Degree in Health and Clinical Management at the International University of Valencia
I think the study is well designed, with a sound statistical analysis. In addition, the study includes a very large number of individuals, with well-recorded data and many variables. I would say that it is the study with the largest sample size studying children conceived by ART [Assisted Reproductive Technologies] over time that I have read about. In Spain, the one study we have published in this area is based on 14,119 children conceived by ART, from the embryo health interest group of the Spanish Fertility Society, which focused on malformations in newborns. It concluded that the percentage of malformations observed in children conceived by ART was similar to the rate observed in the overall Spanish population with spontaneous pregnancy.
There have already been studies along the same lines, examining whether there were differences between children born from ART and those who were not. None of these studies has been able to demonstrate important differences due to the technique itself. In most cases, we assume that one or both gametes are damaged due to age or environmental factors and that a couple does not achieve pregnancy spontaneously. This may be the reason for possible complications, rather than the commonly used microinjection technique. Some studies have linked psychological problems [in children] to their father's advanced age, which are not genetically avoidable. In cases of older mothers-to-be or spermatozoa with a high percentage of chromosomal abnormalities, we can perform a screening or pre-implantation genetic diagnosis, so that embryos generated from damaged gametes, which could give rise to a genetically abnormal embryo, can be selected before embryo transfer. This allows us to select only euploid (chromosomally normal) embryos for transfer.
Other factors that could affect the newborn would be multiple pregnancies, but this has long been avoided by selecting only one embryo for transfer at the blastocyst stage, which is the last stage that can be observed in in vitro culture.
In terms of inclusion and exclusion criteria, many factors were taken into account in the study, such as sex at birth, age at screening, language other than English, socio-economic status, maternal age, parity and education.
Limitations of the study included the use of observational data, the possibility of unmeasured confounding, the presence of missing data and the necessary restriction of the cohort to children in school. However, to overcome some of the limitations of observational (non-randomised) data analysis, the authors used a causal inference approach, which attempts to emulate the results of a randomised comparison in a clinical trial.