Growth rates of human preimplantation embryos fertilized in vitro were assessed and compared to the sex of the pregnancy outcome. The likelihood of a liveborn male was significantly greater than that of a female if the mean number of cells/embryo was four or greater at the scheduled time of transfer (odds ratio of 6:1). This finding suggested that the Y chromosome expresses factors which influence embryonic growth rates immediately after fertilization.
As expected, first-trimester screening is effective for detecting aneuploidy for chromosomes 13, 18, and 21; however, a significant number of chromosomally abnormal pregnancies initially identified by first-trimester screening have a different karyotype. With the possible exception of 47,XYY and 45,X, the dataset suggested that these different chromosome complements were likely to be randomly distributed. Nevertheless, prior to diagnostic testing, prospective parents should be counseled concerning the possibility of a chromosome abnormality other than the trisomies 13, 18, or 21.
Objective The objective of this study was to assess the first formal approach for monitoring genetic/developmental syndromes associated with the presence of an increased nuchal translucency (NT) thickness (>3 mm) in the first trimester of pregnancy.Methods Multiple technologies-a DNA chip using the APEX technology, qPCR, microfluidic PCR, and sequencing-were applied to assay 310 mutations across five conditions-Noonan syndrome, congenital adrenal hyperplasia, spinal muscular atrophy (SMA), DiGeorge syndrome, and Smith-Lemli Opitz syndrome.
ResultsWe report the results of assessing the first 120 patients in which 8 cases of Noonan syndrome were detected as well as an unusually high rate of heterozygosity for SMA.
ConclusionWhile testing for Noonan syndrome in association with increased NT appears warranted, the reported association of the remaining four genetic syndromes is likely to be weak and possibly insignificant.
We have examined the expression of SRY mRNA in individual in vitro fertilized preimplantation human embryos; because of ethical constraints, these studies were confined to embryos with one and three pronuclei. Using a sensitive reverse transcriptase-polymerase chain reaction (RT-PCR) assay, we observed SRY mRNA at the one-cell through the blastula stages but not in spermatozoa. These results indicate that the de novo transcription of this sex-specific gene occurs at a developmental time considerably earlier than that of gonadal differentiation. Our results also indicate that in vitro fertilized embryos with one pronucleus are likely to be diploid.
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