Introduction: Here we report a case of diginyc triploidy, which resulted from the fertilization of a diploid ovum by a single sperm.
Case presentation: A caucasian 24-year-old woman presented in her first pregnancy, naturally conceived. A maternal serum screening and an ultrasound examination was performed to assess the risk of aneuploidy in pregnancy and only the serum screening has raised concerns regarding aneuploidy. After genetic counseling an amniocentesis was performed, showing a 69, XXX karyotype.
Conclusion: Our findings remarked that the first trimester screening at 11-13 weeks' gestation for trisomy is able to detect other chromosomal abnormalities like triploidy.
maternal serum screening, triploidy, prenatal diagnosis, amniocentesis
Triploidy is characterized by an extra haploid chromosome set (3n=69), and resulting in lethal chromosomal abnormalities because most triploid fetuses undergo spontaneous abortion before 20 weeks' gestation: the prevalence of triploidy at the 11-14-week ultrasound scan is approximately 1:3300, the incidence of triploidy in liveborn infants is approximately 1:10.000 [1-3]. The origin of the additional chromosomal set could be maternal (digynic) or paternal (diandric).
A Caucasian 24-year-old woman presented in her first pregnancy, naturally conceived. The obstetric history was negative and the medical history proximate and remote showed no comorbidities. The patient was sent to our ambulatory to perform the first trimester screening for trisomy 21-18 at 11-14 weeks’ gestation. The screening parameters included nucal translucency (NT), maternal serum free β-human chorionic gonadotropin (β-hCG) and pregnancy-associated plasma protein-A (PAPP-A).
The ultrasound and NT measurement was performed by a certified sonographer: NT was 0.9mm (Multiples of median = MoM 0.72), the biometrics was normal, and there were no morphological abnormalities. The maternal serum free β-hCG was 3.69UI/L MoM 0.10 and PAPP-A 0.08UI/L Mom 0.02. The risk of trisomy 21–18 was calculated using a dedicated software (Ssdwlab 5) and there was a low risk: 1:4830 for trisomy 18 and 1:30414 for trisomy 21. There was only a marked decrease in maternal serum free β-hCG and PAPP-A. After genetic counselling, an amniocentesis was recommended in order to exclude aneuploidies related to serum screening.
Amniocentesis was performed at 17 weeks' pregnancy, twenty millimeters of amniotic fluid sample was collected ; which revealed detectable ultrasound abnormalities: bilateral hydrocephalus, agenesis of the corpus callosum, oligohydramnios and asymmetric growth restriction.
The fetus showed a 69, XXX karyotype; the fetus presented intrauterine fetal demise diagnosed at the 18 weeks’ gestation. The chromosomal preparation obtained from fibroblasts confirmed the diagnosis. The postmortem examination findings revealed the intrauterine growth restriction, facial abnormalities. No further pathologic findings were revealed due to fetal maceration.
Triploidy is estimated to occur in 1 % of all conceptions . The prevalence of triploidy at 12 weeks’ gestation is estimated to be 1/3500 compared with 1/30000 at 16 weeks  because a large part of fetuses were aborted during the first and second trimester. A recent study published by Engelbrechtsen and collegue  showed that in their cohort study, the incidence of triploidy is 1:6614, suggesting that triploidy is not as common as shown by others. However there is a great significance attached to detecting triploidy early in pregnancy, because of the risk of maternal complications such as preeclampsia and persistent trophoblastic disease [7-9]; early diagnosis can contribute to an early decision on possible termination of pregnancy and reduced the psychological impact of carrying a fetus with a letal condition.
Increased maternal age isn’t a risk factor in triploidy and there isn’t an increased recurrence risk .
There are two phenotypes of triploidy depending on the origin of the extra haploid chromosome set: the type I diandric if extra haploid chromosome is paternal; type II digynic if extra haploid chromosome is maternal. The different karyotypes result in markedly different phenotypes [11-15].
Type I, the diandric phenotype is characterized by a moderate growth restriction or it is relatively well - grown, proportional body parts and is associated with a large hyperplastic placenta with partial hydatidiform mole changes. First trimester screening usually shows increased NT and levels of free β-hCG in the maternal serum and mildly decreased PAPP-A ; the diandric triploid fetuses are often found to have an increased risk for trisomy 21.
The type II, digynic type, which is the most common, is characterized by a small normal looking placenta and severe asymmetrical growth restriction, with a growth restriction of the trunk and limbs and a normal o large head. The fetal NT is normal, with markedly decreased maternal serum total free beta-hCG and PAPP-A. Previous studies have confirmed this serological picture in the two phenotypes [17,18].
Digynic triploid fetuses can be difficult to detect at first-trimester screening. A number of characteristic abnormalities are common in both types and there is no difference between the two phenotypes: the anomalies of the brain, heart and urinary tract, abnormal genitals and syndactyly of the third or fourth fingers and of the toes [11-13,19-22].
In our case, the biochemical findings were comparable with the result s of the previous report of maternal origin: serum free β-hCG was 3.69UI/L MoM 0.10 and PAPP-A 0.08UI/L MoM 0.02 was very low. The NT was normal, and the risk of trisomy 21-18 was not increased. Our report remarked that there was a large deviation in the maternal serum and the biochemistry of fetus with digynic triploidy is to be identified during the first trimester screening. In fact the risk of triploidy is not related to maternal age and other sonographic markers don't show substantially different values in euploid fetuses [23,24].
Anyway, in our case there was not a severe intrauterine growth restriction at the first ultrasound scan.
Our findings remarked that the first trimester screening at 11-13 weeks' gestation for trisomy is able to detect other chromosomal abnormalities like triploidy.
Other study demonstrate that maternal serum screening in the first trimester of pregnancy are able to detect triploid fetuses. Our study add a case of digynic triploid fetus, without ultrasound anomalies, but only with anomalies of maternal serum biochemistry.
The author(s) declare that they have no competing interests.
- Jauniaux E, Brown R, Snijders RJ, Noble P, Nicolaides KH (1997) Early prenatal diagnosis of triploidy. Am J Obstet Gynecol 176: 550–554. [Crossref]
- Ferguson-Smith MA, Yates JR (1984) Maternal age specific rates for chromosome aberrations and factors influencing them: report of a collaborative European study on 52 965 amniocenteses. Prenat Diagn 4 (Spec No): 5–44. [Crossref]
- Jacobs PA, Szulman AE, Funkhouser J, Matsuura JS, Wilson CC (1982) Human triploidy: relationship between parental origin of the additional haploid complement and development of partial hydatidiform mole. Ann Hum Genet 46: 223–231. [Crossref]
- Jacobs PA, Angell RR, Buchanan IM, Hassold TJ, Matsuyama AM, et al. (1978) The origin of human triploids. Ann Hum Genet 42: 49-57. [Crossref]
- Snijders RJ, Sebire NJ, Nicolaides KH (1995) Maternal age and gestational age-specific risk for chromosomal defects. Fetal Diagn Ther 10: 356-67. [Crossref]
- Engelbrechtsen L, Brøndum-Nielsen K, Ekelund C, Tabor A, Skibsted L (2013) Detection of triploidy at 11–14weeks’ gestation: a cohort study of 198 000 pregnant women. Ultrasound Obstet Gynecol 42: 530–535. [Crossref]
- Hsieh CC, Hsieh TT, Hsueh C, Kuo DM, Lo LM, et al. (1999) Delivery of a severely anaemic fetus after partial molar pregnancy: clinical and ultrasonographic findings. Hum Reprod 14: 1122–1126. [Crossref]
- Rijhsinghani A, Yankowitz J, Strauss RA, Kuller JA, Patil S, et al. (1997) Risk of preeclampsia in second-trimester triploid pregnancies. Obstet Gynecol 90: 884–888. [Crossref]
- Goldstein DP, Berkowitz RS (1994) Current management of complete and partial molar pregnancy. J Reprod Med 39: 139–146. [Crossref]
- Dalmia R, Young P, Sunanda GV (2005) A case of triploidy. Fertil Steril 83: 462-463.
- McFadden DE, Kalous2021 Copyright OAT. All rights reserv of fetuses with chromosomal triploidy: correlation with parental origin of the extra haploid set. Am J Med Genet 38: 535–538. [Crossref]
- McFadden DE, Kwong LC, Yam IY, Langlois S (1993) Parental origin of triploidy in human fetuses: evidence for genomic imprinting. Hum Genet 92: 465–469. [Crossref]
- McFadden DE, Hulait G, Lockitch G, Langlois S (2002) Maternal serum screening in triploidy. Prenat Diagn 22: 1113–1114.
- McFadden DE, Robinson WP (2006) Phenotype of triploid embryos. J Med Genet 43: 609–612. [Crossref]
- Barken SS, Skibsted L, Jensen LN, Sperling L, Zingenberg H, et al. (2008) Diagnosis and prediction of parental origin of triploidies by fetal nuchal translucency and maternal serum free beta-hCG and PAPP-A at 11–14 weeks of gestation. Acta Obstet Gynecol Scand 87: 975–978. [Crossref]
- Yaron Y, Ochshorn Y, Tsabari S, Shira AB (2004) First trimester nuchal translucency and maternal serum free beta-hCG and PAPP-A can detect triploidy and determine the parental origin. Prenat Diagn 24: 445-450. [Crossref]
- Benn PA, Gainey A, Ingardia CJ, Rodis JF, Egan JF (2001) Second trimester maternal serum analysis in triploid pregnancies: correlation with phenotype and sex chromosome complement. Prenat Diagn 21: 680-686. [Crossref]
- Huang T, Alberman E, Wald N, Summers AM (2005) Triploidy identified through second-trimester serum screening. Prenat Diagn 25: 229-233. [Crossref]
- Dietzsch E, Ramsay M, Christianson AL, Henderson BD, de Ravel TJ (1995) Maternal origin of extra haploid set of chromosomes in third trimester triploid fetuses. Am J Med Genet 58: 360–364. [Crossref]
- Jauniaux E, Brown R, Rodeck C, Nicolaides KH (1996) Prenatal diagnosis of triploidy during the second trimester of pregnancy. Obstet Gynecol 88: 983–989. [Crossref]
- Yaron Y, Ochshorn Y, Tsabari S, Shira AB (2004) First-trimester nuchal translucency and maternal serum free beta-hCG and PAPP-A can detect triploidy and determine the parental origin. Prenat Diagn 24: 445–450. [Crossref]
- Spencer K, Liao AW, Skentou H, Cicero S, Nicolaides KH (2000) Screening for triploidy by fetal nuchal translucency and maternal serum free beta-hCG and PAPP-A at 10–14 weeks of gestation. Prenat Diagn 20: 495–499. [Crossref]
- Kagan KO, Anderson JM, Anwandter G, Neksasova K, Nicolaides KH (2008) Screening for triploidy by the risk algorithms for trisomies 21, 18 and 13 at 11 weeks to 13 weeks and 6 days of gestation. Prenat Diagn 28: 1209–1213. [Crossref]
- Spencer K1, Liao AW, Skentou H, Cicero S, Nicolaides KH (2000) Screening for triploidy by fetal nuchal translucency and maternal serum free b-hCG and PAPP-A at 10±14 weeks of gestation. Prenat Diagn 20: 495-499. [Crossref]