Department of Gynecology and Obstetrics and Prenatal Diagnosis, A. Cardarelli Hospital, Naples, Italy.

 
Introduction

Placental aneuploidy associated with normal fetal karyotype is a very rare finding. Only few cases have been described in the literature. The prevalence among the chorionic villus sampling cases is between 60-150 : 10 000, which represents 0,005-0,01% of all pregnancies. The relationship of placental pathology to an adverse pregnancy outcome has been well recognized.

In the literature, we found only 106 described cases in the last ten years. Increasing number of the cytogenetic studies have led to the discovery of cytogenetic discrepancies between chorionic villi and fetal tissues (1). More recently, there were several reported cases of the mosaicism of a chromosome aneuploidy both in the placenta and in the fetus (2). The incidence of this finding is reported to be between 0,005-0,01% of all pregnancies (3).

The diagnosis before 14 weeks of gestation is difficult. Sonographic findings include thick placenta and severe growth retardation. The rate of the placental growth is unpredictable, but spontaneous abortion occurs usually before 20 weeks of gestation due to a fetal compression by placental tissue that fills the entire uterine cavity.

The counseling of the patient is very important because placental triploidy is always associated with an adverse pregnancy outcome. This is contrary to placental mosaicism or trisomy, which do not necessarily lead to an abnormal pregnancy outcome.

Case report

This is a case of a 27-year-old caucasian woman G1 P0, who was referred to our department during her 17th week of gestation. She complained of a vaginal bleeding which started around 15 weeks of gestation.
The ultrasound examination upon admission to the hospital showed a severely growth restricted fetus compressed by the thick placenta. We did not see any other fetal abnormalities except of the small omphalocele.
Placenta had a homogenous structure and it's vascularization, demonstrated by Doppler, seemed normal. Placenta showed high growth rate. Fetus measured 13 weeks (less than 2 SD). Spontaneous abortion occurred within five days, at 18 weeks of gestation.
Macroscopic examination of the placenta revealed multiple areas with vascular degeneration. The fetus had a small omphalocele. The fetal karyotype was normal. Cytogenetic examination of the placenta confirmed our suspicion of the placental triploidy.

Conclusion

Following ultrasound findings can be considered as a markers for the placental triploidy:

• Thick placenta
  
• High placental growth rate
  
• Homogenous structure of the placenta
  
• Severe intrauterine growth restriction
  
  

Images 1,2:  Images show thick placenta of homogenous structure.

References:

1. Thomas D. et all:  Trisomy 22, placenta.  The Fetus.net 1994-07-10-18
2. Sciorra LJ, Hux C, Day Salvadore D, et al.: Trisomy 5 mosaicism detected prenatally with an affected liveborn. Prenat Diagn 12:477-482, 1992.
3. Kalousek DK, Howard-Peebles PN, Olson SB, et al.: Confirmation of chorionic villi sampling mosaicism in term placentas and high frequency of intrauterine growth retardation: Association with confined placental mosaicism. Prenat Diagn 11: 743-750, 1991.
4. Shih J.C., Ko T.L. et al.:Quantitative three-dimensional power Doppler ultrasound predicts the outcome of placental chorioangioma. Ultrasound Obstet Gynecol 2004; 24: 202-206
5. Marino T.: Ultrasound abnormalities of the amniotic fluid, membranes, umbilical cord, and placenta. Obstet Gynecol Clin North Am. 2004 Mar;31(1):177-200.
6. Ghezzi F., Raio L., Di Naro E., Franchi M., Buttarelli M., Schneider H.: First-trimester umbilical cord diameter: a novel marker of fetal aneuploidy. Ultrasound Obstet Gynecol. 2002 Mar;19(3):235-9.