Second-Trimester Diagnosis of Triploidy: A Series of Four Cases

Abstract

Triploidy occurs in 2 to 3% of conceptuses and accounts for approximately 20% of chromosomally abnormal first-trimester miscarriages. As such, triploidy is estimated to occur in 1 of 3,500 pregnancies at 12 weeks', 1 in 30,000 at 16 weeks', and 1 in 250,000 at 20 weeks' gestation. We present a series of four cases of second-trimester triploidy diagnosed at our center within a 1-year timeframe. This is remarkable, as the delivery volume at our institution is roughly 2,500/y. All patients were at least 19 weeks' gestation, with multiple abnormalities identified on prenatal ultrasound at 18 to 20 weeks' gestation; all fetuses had lethal anomalies, but anomalies were not consistent between cases. All patients elected for induction of labor before 24 weeks' gestational age. Two of the four cases had amniocentesis and chromosome analysis prior to delivery, and two cases had chromosome analysis performed on fetal tissue after delivery. All fetuses were examined following delivery. This case series demonstrates that the diagnosis of triploidy may not be obvious based on ultrasound and physical examination findings and highlights the importance of routine chromosome analysis on all prenatal diagnoses of multiple congenital anomalies prior to consideration of more complex genetic testing.

Chromosome aberrations in a large series of spontaneous miscarriages in the German population and review of the literature

“…Of all 16-week pregnancies, only 1 in 30,000 is estimated to be triploid [ 30 ]. Surprisingly, Wick and coworkers [ 31 ] detected four cases of second-trimester triploidy (all patients were at least 19 weeks’ gestation) which were diagnosed at a tertiary centre within a 1-year period, so that some of the triploid karyotypes survived longer. Generally a high rate of triploidy has been observed in spontaneous miscarriages by CA.…”

Genetic Counseling and Prenatal Diagnosis of Triploidy During the Second Trimester of Pregnancy

“…Only 1 in 1,200 triploid fetuses live after birth. The frequency of triploidy in live births is 1:10,000, and males represent 51-69 % of all cases ( 1 , 6 ).…”

“…Anomaly also includes single umbilical artery ( 3 , 4 , 5 ). The low frequency of triploidy among advanced pregnancies has led to discrepancies in prevalence estimates, ranging from as low as 1 in 250,000 at 20 weeks to as high as 1 in 50,000 among live-born infants ( 6 , 7 ). It can be recurrent, and maternally derived cases appear to live longer than paternally derived cases.…”

Identification of trisomy 18, trisomy 13, and Down syndrome from maternal plasma

“…Also, for monosomy X, the failure rate could be as high as 13% of samples analyzed 18,26,27,38. In addition, triploidies occur in 2%–3% of conceptuses and are estimated to occur in 1 in 30,000 pregnancies at 16 weeks 40. The fact that gNIPT testing may not accurately guarantee their detection40–42 highlights the importance of routine chromosome analysis on all prenatal diagnoses with multiple congenital anomalies prior to the consideration of more complex genetic testing 40.…”

“… 18 , 26 , 27 , 38 In addition, triploidies occur in 2%–3% of conceptuses and are estimated to occur in 1 in 30,000 pregnancies at 16 weeks. 40 The fact that gNIPT testing may not accurately guarantee their detection 40 – 42 highlights the importance of routine chromosome analysis on all prenatal diagnoses with multiple congenital anomalies prior to the consideration of more complex genetic testing. 40 In a study evaluating the diagnostic yield of chromosomal microarray analysis as compared with karyotyping for routine prenatal diagnosis, in samples with a normal karyotype, microarray analysis revealed clinically relevant deletions or duplications in 6.0% of fetuses with a structural anomaly seen at ultrasonography and in 1.7% of those whose indications were advanced maternal age or positive screening results.…”