Mosaicism in chorionic villus sampling: an association with poor perinatal outcome

Article Abstract:

A relatively new method of prenatal diagnosis consists of sampling chorionic villus tissue (uterine tissue that contains fetal cells) during the early weeks of pregnancy. The significance of mosaicism, a kind of chromosomal abnormality identified in this way, has not been determined. Mosaicism refers to the situation when chromosomes from two genetically distinct individuals, rather than one, are detected. A fetus with true mosaicism is likely to develop abnormally, but mosaicism appears more frequently in sampled material as the result of contamination by maternal cells; changes in the cells when they are grown in tissue culture; or the death of a twin in embryonic life. In these cases mosaicism is not meaningful. Mosaicism can also be confined to the placenta, where its associations with perinatal outcome are unclear. This was explored by evaluating the outcomes of 4,319 pregnancies (4,395 fetuses), of which 49 involved placentas with mosaicism. The specific types of mosaicism are listed. There were no differences in maternal age, number of previous pregnancies, previous miscarriages, or related factors, between mosaic and nonmosaic pregnancies. However, more mosaic pregnancies (16.7 percent versus 2.7 percent) ended with loss of the fetus before birth. How the function of the placenta is affected by the abnormal cells is not known. The diagnostic problems presented by mosaicism in chorionic villus sampling are reviewed; ultimately, the clinician decides what kinds of mosaicism have meaning for the fetus. Technical considerations are discussed; it is more likely that cells from one region of the chorionic villus (its core) are fetal cells than cells from the cytotrophoblast (another region). (Consumer Summary produced by Reliance Medical Information, Inc.)

Research, Methods, Evaluation, Prognosis, Mosaicism, Prenatal diagnosis, Chorionic villus sampling

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Multifetal pregnancy reduction: evaluation of fetal growth in the remaining twins

Article Abstract:

Selective reduction of multifetal pregnancies may not reduce the risk of gestational growth restriction in the remaining fetuses. Researchers compared the birth weights and gestational ages from twin pregnancies that had been reduced from triplet, quadruplet, or more pregnancies to those of twins from unreduced pregnancies. Intrauterine growth restriction was greatest in the remaining twin fetuses from quintuplet or higher pregnancies, with the growth of these twins 50% that of a normal single birth. Intrauterine growth restriction was 19.4% in unreduced twins, 36.3% among triplet pregnancies reduced to twins, and 41.6% in twins reduced from quadruplet pregnancies. Measures should be taken by assisted reproduction providers to avoid multifetal pregnancies in the first place.

Care and treatment, Fetus, Growth, Fetal growth retardation, Twins, Pregnancy, Multiple, Multiple pregnancy

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