Follow-up of Children Born After Preimplantation Genetic Diagnosis
Preimplantation genetic diagnosis (PGD) offers couples at risk for transmitting genetic diseases an alternative to prenatal diagnostic testing (chorionic villus sampling or amniocentesis). Couples opting for PGD must first undergo IVF treatment to obtain embryos for genetic analysis. Typically the peripheral, placental-generating (trophectodermal) cells of blastocysts (day 5 embryos) are biopsied and analyzed for a specific genetic defect or a chromosomal abnormality.
In the current edition of the Journal of Assisted Reproduction and Genetics is a study from the Netherlands that looked at the safety of PGD from 1995-2014. The primary focus was on the congenital malformation rate as well as misdiagnosis, birth parameters, perinatal mortality and morbidity. A secondary focus was: “Is PGD a justifiable tool in prevention of heritable diseases?”
The authors reviewed 439 pregnancies in 381 women that resulted in 364 live born children. The modes of inheritance in this study were as follows: autosomal dominant (39.1%), chromosomal (27.6%), X-linked (17.5%), autosomal recessive (14.8%), and mitochondrial (0.9%). Nine children (2.5%) had major malformations and this percentage is consistent with other PGD registries and comparable to the prevalence reported by the European Surveillance of Congenital Anomalies. There was one misdiagnosis resulting in the miscarriage of a fetus with an unbalanced chromosome pattern and 20% of the children were born premature (< 37 weeks) and less than 15% had a low birth weight. One child from a twin, one child from a triplet, and one singleton died at 23, 32, and 37 weeks of gestation respectively.
It should be noted, because this study includes the early years of PGD, that older genetic analysis techniques were employed and only one or two cells of the embryo were biopsied. Presently, comparative genomic hybridization (CGH), a fantastically more sensitive method, is used to analyze the 5-8 cells of the biopsy. More biopsied cells mean more DNA available and increased accuracy of the diagnosis. This study also did not include preimplantation genetic screening for abnormal chromosome copy testing, commonly used in IVF for patients with advanced reproductive age, recurrent miscarriage history and failed IVF implantation(s).
The conclusion of the study is that overall, the risk on major malformations in PGD children seems comparable to children born after IVF-ICSI, as well as to the risk reported in naturally conceived children. Data on pregnancy duration, birth weight, perinatal mortality, and hospital admissions in the PGD population, especially in the singletons, appear to be similar to the published data on naturally conceived children. In conclusion, PGD does not seem to be associated with an increased risk for adverse birth outcome when compared to naturally conceived children. Indeed, PGD does seem to be an important and justifiable technique for avoiding transmission of genetic diseases.
Heijligers, M., van Montfoort, A., Meijer-Hoogeveen, M. et al. J Assist Reprod Genet (2018) 35: 1995. https://doi.org/10.1007/s10815-018-1286-2