Confined placental mosaicism revisited: Impact on pregnancy characteristics and outcome

Abstract

Objectives: We wanted to re-evaluate the influence of confined placental mosaicism subtypes (type 2 and type 3) on pregnancy characteristics and outcome.

Material and methods: From July 2009 to December 2015, 5512 chorionic villus samplings were performed in our Fetal Medicine Center. Conventional karyotyping was performed after long-term and short-term cultured villi to define type 2 or type 3 confined placental mosaicisms. Karyotype after amniocentesis was performed to exclude true fetal mosaicism, when appropriate. Pregnancy characteristics and outcomes were collected and compared to a control population.

Results: Thirty-six (0.65%) confined placental mosaicisms were observed (13 type 2 and 23 type 3). Nuchal translucency was not increased for type 2 and type 3 confined placental mosaicisms. Pregnancy characteristics and outcomes were comparable between type 2 confined placental mosaicisms and the control population. In type 3 confined placental mosaicisms, median first trimester serum pregnancy-associated plasma protein A was lower than for the control population (p<0.001), preterm births were noticed in 56% (p<0.001), small for gestational age newborns in 74% (p<0.001), and adverse pregnancy outcome was reported in 35% (p<0.01).

Conclusion: Although type 2 confined placental mosaicisms appeared to have no influence on pregnancy characteristics and outcome, type 3 confined placental mosaicisms were associated with low levels of first trimester serum pregnancy-associated plasma protein A, preterm birth, small for gestational age newborns, and adverse pregnancy outcomes.

Fig 1. Distribution of chromosomal abnormalities observed in 36 confined placental mosaicisms (CPM) (CPM2: Type 2 CPM; CPM3: Type 3 CPM).

Fig 2. First trimester free beta-human chorionic gonadotropin and serum pregnancy-associated plasma protein A levels, and confined placental mosaicisms (CPM).

A. Distribution of first trimester free beta-human chorionic gonadotropin (β-HCG) for the control population, type 2 confined placental mosaicisms (CPM2) and type 3 confined placental mosaicisms (CPM3). B. Distribution of first trimester serum pregnancy-associated plasma protein A (PAPP-A) for the control population, CPM2 and CPM3 (***: p<0.001; MoM: multiple of the median; NS: non significant).

Fig 3. Association between birth weight and percentage of placental cells with chromosomal abnormalities after long-term cultured villi for type 2 confined placental mosaicisms (CPM2) and type 3 confined placental mosaicisms (CPM3) (Pearson's correlation coefficient = -0.61, p<0.001).

Fig 4. Type 2 confined placental mosaicisms (CPM2) and type 3 confined placental mosaicisms (CPM3) diagnosed in the fetal medicine center of the University Hospital of Bordeaux (France) from 19321 chorionic villus samplings performed between 1997 and 2015.

A. Weight and gestation age at delivery for CPM2 and CPM3, and a control population. B. Association between birth weight percentile and percentage of placental cells with chromosomal abnormalities after long-term cultured villi for CPM2 and CPM3 (Pearson's correlation coefficient = -0.34, p<0.01).