Summary. Confined placental chorionic mosaicism is reported in 2% of viable pregnancies cytogenetically analyzed on chorionic villi samplings (CVS) at 9-12 weeks of gestation. In follow-up studies this mosaicism has been shown to be associated with increased frequency of second and third trimester pregnancy loss or intrauterine fetal growth retardation. We have studied 54 spontaneous abortions (SA) for the detection of confined placental mosaicism and found 11 of them to be mosaic. All mosaic cases were identified among first trimester spontaneous abortions, and the mosaicism was confined to specific placental or embryonic/fetal cell lineages. These results indicate that the previously reported mosaicism in SA represents both confined and generalized types of mosaicism and that its accepted frequency of 5%-10% in SA will likely be higher. Over the whole gestational period, the confined placental mosaicism is more common than the reported rate of 1%-2% seen in viable pregnancies at CVS, and a higher proportion of pregnancy complications than previously suspected may be associated with confined placental mosaicism.

We studied the structure and number of lymph vessels in 12 spontaneously aborted previable fetuses with posterior cervical cystic hygroma and generalized edema of variable origin (monosomy X, trisomy 21, trisomy 13, suspected Noonan syndrome, and lethal multiple pterygium syndrome) and compared them to 5 therapeutically aborted, apparently normal fetuses. We found that in the non-45,X fetuses with cystic hygroma and edema the lymphatic vessels at all studied sites were dilated and appeared increased in number. The 45,X fetuses had no recognizable lymphatic vessels in the edematous cutaneous tissue of the limbs, and only occasional dilated vessels in the wall of the nuchal cystic hygroma and in the lungs. These findings may be useful in differentiating between monosomy X and other conditions causing nuchal cystic hygroma in specimens in which the fetus was incomplete and/or cytogenetic study could not be done.

We studied G-banded chromosome complements on 318 couples with 2 or more spontaneous abortions. Seven chromosome abnormalities were detected. Three women and one man were identified as carriers of balanced Robertsonian translocations, t(13;14), t(13;14), t(13;21), and t(14;22), respectively. Aneuploidy: 47,XXX; 47,XX, + marker; and 45,X/46,XX/47,XXX were found in the other 3 women. The overall aberration frequency was 2.2% of couples. When a stringent criterion of greater than or equal to 3 consecutive spontaneous abortions was used, the frequency was 4.2%. In this series no chromosome aberrations were identified in couples with 2 spontaneous abortions and a live-born child with congenital anomalies; 1 of 22 couples with 2 spontaneous abortions and a still-born infant showed a chromosomal abnormality. Findings from the recent literature are compared with those from this study.

No abstract