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PubMed This is a summary of 17 peer-reviewed journal articles Updated
Obstetrics · Triploidy

The Basics of Triploidy

At a Glance

Triploidy is a lethal chromosomal condition where a baby has 69 chromosomes instead of the typical 46. It is a random, non-preventable accident during fertilization that usually results in miscarriage. It is not caused by parental actions and rarely happens again in future pregnancies.

Receiving a diagnosis of triploidy is a life-altering moment. Please give yourself grace as you navigate the medical facts and your personal grief.

What is Triploidy?

Triploidy is a chromosomal condition where a baby has an entire extra set of chromosomes. In a typical pregnancy, a baby receives 23 chromosomes from the mother and 23 from the father, for a total of 46 chromosomes in every cell. In triploidy, there are three sets of chromosomes instead of two, totaling 69 chromosomes [1][2].

This extra genetic material changes the way the baby and the placenta develop. There are two main ways this happens:

  • Diandric (Type I): The extra set of chromosomes comes from the father, often because two sperm fertilized one egg [3][4].
  • Digynic (Type II): The extra set of chromosomes comes from the mother, usually because the egg did not properly divide before fertilization [5][6].

Why Did This Happen?

For the vast majority of families, triploidy is a sporadic accident—a random occurrence during fertilization [7][5]. It is a glitch in the complex process of combining genetic material. Importantly, taking or missing prenatal vitamins, such as folic acid, does not cause or prevent triploidy.

Because it is almost always a random event, the risk of it happening again in a future pregnancy is generally very low [7]. While there are extremely rare cases where a genetic predisposition might exist, for most parents, this is a one-time event [6].

Understanding the Incidence

Triploidy occurs in about 1% to 2% of all pregnancies [8]. Because the chromosomal imbalance is so severe, it is a leading cause of early miscarriage, accounting for roughly 10% to 20% of miscarriages that occur in the first trimester [8][1].

What This Means for the Pregnancy

Triploidy is a lethal condition, meaning it is not compatible with long-term life [9][10]. The extra chromosomes interfere with the development of vital organs and systems in ways that cannot be corrected.

  • Miscarriage: The most common outcome is a spontaneous miscarriage, often in the first trimester [11][12].
  • Growth Restriction: If the pregnancy continues, the baby often experiences severe growth restriction (intrauterine growth restriction or IUGR) and may have low levels of amniotic fluid (oligohydramnios) [13][14].
  • Neonatal Survival: In very rare cases, a baby may be born alive. However, these infants usually only survive for a few hours or a few days due to the severity of the malformations [9][15].

When and How It Appears

Doctors may identify triploidy through specific signs on an ultrasound. The timeline of when these signs appear often depends on the type:

  • First Trimester: Diandric triploidy is often suspected early on because it causes profound, visible changes to the placenta [3].
  • Second Trimester: Digynic triploidy may not be suspected until the 18-to-20-week anatomy scan, when severe fetal growth restriction becomes apparent [16].

Physical markers on an ultrasound may include webbing or fusing of the third and fourth fingers or toes (syndactyly) or brain abnormalities like holoprosencephaly (where the brain does not divide into two hemispheres correctly) [13][17].

Common questions in this guide

What causes triploidy to happen?
Triploidy is almost always a random, sporadic accident during fertilization where a baby receives an extra set of chromosomes. It is a genetic glitch and is not caused by anything the parents did or did not do, such as missing prenatal vitamins.
Can a baby survive with triploidy?
Triploidy is a lethal condition that is not compatible with long-term life. Most pregnancies with this condition result in a miscarriage. In the very rare cases where a baby is born alive, they typically only survive for a few hours or days due to severe malformations.
What is the difference between diandric and digynic triploidy?
In diandric triploidy (Type I), the extra set of chromosomes comes from the father, often causing visible changes to the placenta early in pregnancy. In digynic triploidy (Type II), the extra set comes from the mother and usually presents later on ultrasound as severe fetal growth restriction.
Will triploidy happen again in a future pregnancy?
Because triploidy is almost always a random genetic error during fertilization, the risk of it occurring again in a future pregnancy is generally very low. For the vast majority of families, this is a one-time event.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Based on the ultrasound, does the baby have signs of diandric or digynic triploidy?
  2. 2.What is the specific timeline for when these physical changes usually appear on an ultrasound?
  3. 3.Are there any physical signs that I am already developing complications from this pregnancy?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (17)
  1. 1

    Digynic monoandric triploidy in the setting of recurrent pregnancy loss: a case report and literature review.

    Raymond C, Han S, Huang G, et al.

    Laboratory medicine 2024; (55(1)):103-105 doi:10.1093/labmed/lmad036.

    PMID: 37184333
  2. 2

    Single-nucleotide polymorphism microarray detects molar pregnancies in 3% of miscarriages.

    Maisenbacher MK, Merrion K, Kutteh WH

    Fertility and sterility 2019; (112(4)):700-706 doi:10.1016/j.fertnstert.2019.06.015.

    PMID: 31395308
  3. 3

    The Contribution of QF-PCR and Pathology Studies in the Diagnosis of Diandric Triploidy/Partial Mole.

    Benítez L, Pauta M, Badenas C, et al.

    Diagnostics (Basel, Switzerland) 2021; (11(10)) doi:10.3390/diagnostics11101811.

    PMID: 34679509
  4. 4

    Molecular genetic study of triploidy and the hydatidiform mole in pregnancy loss: analysis of 10,000 consecutive cases.

    Pushkarev VP, Masycheva AS, Glazyrina EA, et al.

    Vavilovskii zhurnal genetiki i selektsii 2025; (29(5)):621-628 doi:10.18699/vjgb-25-67.

    PMID: 41000402
  5. 5

    Prenatal Diagnosis of Triploidy in Fetus with Unexpected Chromosomal Translocation of Maternal Origin.

    Jadhav A, Jadhav Y, Bhairi V, et al.

    International journal of molecular and cellular medicine 2023; (12(1)):81-85 doi:10.22088/IJMCM.BUMS.12.1.81.

    PMID: 37942256
  6. 6

    Biallelic variant in cyclin B3 is associated with failure of maternal meiosis II and recurrent digynic triploidy.

    Fatemi N, Salehi N, Pignata L, et al.

    Journal of medical genetics 2021; (58(11)):783-788 doi:10.1136/jmedgenet-2020-106909.

    PMID: 32938693
  7. 7

    Recurrent fetal triploidy: is there a genetic cause?

    Fontoura Oliveira A, Torrão MM, Nogueira R, Ferreira M

    BMJ case reports 2021; (14(3)) doi:10.1136/bcr-2020-239843.

    PMID: 33653854
  8. 8

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

    Kolarski M, Ahmetovic B, Beres M, et al.

    Medical archives (Sarajevo, Bosnia and Herzegovina) 2017; (71(2)):144-147 doi:10.5455/medarh.2017.71.144-147.

    PMID: 28790549
  9. 9

    Extended survival of a premature infant with a postnatal diagnosis of complete triploidy.

    Walsh R, Sharma A

    BMJ case reports 2022; (15(2)) doi:10.1136/bcr-2021-244551.

    PMID: 35131773
  10. 10

    Naturally occurring horse model of miscarriage reveals temporal relationship between chromosomal aberration type and point of lethality.

    Lawson JM, Salem SE, Miller D, et al.

    Proceedings of the National Academy of Sciences of the United States of America 2024; (121(33)):e2405636121 doi:10.1073/pnas.2405636121.

    PMID: 39102548
  11. 11

    Polyploidy Phenomenon as a Cause of Early Miscarriages in Abortion Materials.

    Yildirim ME, Karakus S, Kurtulgan HK, et al.

    Balkan journal of medical genetics : BJMG 2023; (26(1)):5-10 doi:10.2478/bjmg-2023-0002.

    PMID: 37576791
  12. 12

    Screening of triploid in miscarriage tissues using medium-coverage whole genome sequencing with a three-algorithm integrated approach.

    Zheng J, Zhang Q, Xu L, et al.

    Journal of assisted reproduction and genetics 2025; (42(9)):3133-3142 doi:10.1007/s10815-025-03607-1.

    PMID: 40750717
  13. 13

    Prenatal sonographic features can accurately determine parental origin in triploid pregnancies.

    Lugthart MA, Horenblas J, Kleinrouweler EC, et al.

    Prenatal diagnosis 2020; (40(6)):705-714 doi:10.1002/pd.5666.

    PMID: 32039494
  14. 14

    Digynic triploidy: utility and challenges of noninvasive prenatal testing.

    Fleischer J, Shenoy A, Goetzinger K, et al.

    Clinical case reports 2015; (3(6)):406-10 doi:10.1002/ccr3.247.

    PMID: 26185638
  15. 15

    Triploidy in a Live-Born Extremely Low Birth Weight Twin: Clinical Aspects.

    Vakrilova L, Hitrova-Nikolova S, Bradinova I

    Journal of pediatric genetics 2022; (11(3)):227-231 doi:10.1055/s-0040-1716828.

    PMID: 35990033
  16. 16

    Digynic triploidy in a fetus presenting with semilobar holoprosencephaly.

    Chuang TY, Chang SY, Chen CP, et al.

    Taiwanese journal of obstetrics & gynecology 2018; (57(6)):881-884 doi:10.1016/j.tjog.2018.11.001.

    PMID: 30545546
  17. 17

    Triploidy: Variation of Phenotype.

    Toufaily MH, Roberts DJ, Westgate MN, Holmes LB

    American journal of clinical pathology 2016; (145(1)):86-95 doi:10.1093/ajcp/aqv012.

    PMID: 26712875

This page provides basic educational information about triploidy syndrome. It is not a substitute for professional medical advice, diagnosis, or genetic counseling from your healthcare provider.

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