[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Embryology](https://durgical.com/en/embryology/) › [Teratology and prenatal diagnosis](https://durgical.com/en/embryology/#a-teratology) › TORCH infections: what each agent does to the embryo and fetus [Embryology](https://durgical.com/en/embryology/) · [Teratology and prenatal diagnosis](https://durgical.com/en/embryology/#a-teratology) # TORCH infections: what each agent does to the embryo and fetus - Teratogen Maternal infections that cross the placenta or pass during birth and can harm the baby's brain, eyes, ears and heart. Updated 2026-11-01 **See it in 3D:** [Retina](https://durgical.com/en/anatomy/retina/) · [Cochlea](https://durgical.com/en/anatomy/cochlea/) · [Lens](https://durgical.com/en/anatomy/lens/) · [Lateral ventricles](https://durgical.com/en/anatomy/lateral-ventricle/) · [Liver](https://durgical.com/en/anatomy/liver/) ## Key points - Toxoplasma: chorioretinitis, hydrocephalus and diffuse intracranial calcifications. - CMV: the commonest infectious cause of birth defects and the leading non-genetic cause of deafness; periventricular calcifications. - Rubella: cataracts, sensorineural deafness and heart disease (patent ductus arteriosus). - Late syphilis: Hutchinson teeth, interstitial keratitis and deafness; early: rhinitis, palm-and-sole rash, hepatosplenomegaly. - Herpes simplex: almost always acquired at birth; vesicles, encephalitis or disseminated disease. ## What it is TORCH groups the agents that infect the embryo or fetus: toxoplasma, 'other' (syphilis, varicella, parvovirus B19, Zika, Listeria), rubella, cytomegalovirus and herpes simplex. They share signs at birth, but each has classic findings that point to the diagnosis. Early infection tends to cause malformations; late infection tends to cause active neonatal infection. ## Key facts - Shared signs: growth restriction, hepatosplenomegaly, jaundice, petechiae and thrombocytopenia. - Many infected newborns have no symptoms at birth and develop deafness or visual problems later. - Congenital varicella: dermatomal skin scars, limb hypoplasia and eye lesions; risk highest between weeks 13 and 20. - Parvovirus B19: infects red cell precursors and causes severe fetal anaemia and hydrops. - Zika: severe microcephaly with subcortical calcifications and macular lesions. ## Critical period and mechanism - Most arrive across the placenta after a primary maternal infection; herpes simplex is mainly passed in the birth canal. - First trimester: infection disrupts organogenesis and causes malformations (rubella, varicella, severe toxoplasmosis). - Later: active infection of the fetus or newborn predominates (hepatitis, encephalitis, sepsis). - Mechanisms: death of progenitor cells, inflammation with calcification, and vascular damage. ## Prevention - Rubella and varicella vaccination before pregnancy (live vaccines, not given during pregnancy). - Toxoplasma: avoiding undercooked meat and contact with cat faeces or contaminated soil. - CMV: hand hygiene after contact with young children's saliva or urine, and not sharing utensils. - Syphilis screening and treatment in prenatal care; protection from mosquito bites (Zika). ## TORCH agent and classic findings | Agent | Classic findings | | --- | --- | | [Toxoplasma gondii (toxoplasma_gondii)](https://durgical.com/en/conditions/congenital-infections-syphilis-toxoplasmosis-cmv-and-zika/) | Chorioretinitis, hydrocephalus, diffuse calcifications | | [Treponema pallidum (treponema_pallidum)](https://durgical.com/en/conditions/syphilis/) | Rhinitis, palm-and-sole rash; later Hutchinson teeth, saddle nose | | [Rubella virus (rubella_virus)](https://durgical.com/en/conditions/congenital-infections-syphilis-toxoplasmosis-cmv-and-zika/) | Cataracts, deafness, patent ductus arteriosus | | [Cytomegalovirus (cmv)](https://durgical.com/en/conditions/hearing-loss/) | Microcephaly, periventricular calcifications, deafness | | [Herpes simplex (hsv_2, hsv_1)](https://durgical.com/en/conditions/genital-herpes/) | Vesicles, encephalitis, disseminated disease | | [Varicella-zoster (varicella_zoster_virus)](https://durgical.com/en/conditions/varicella/) | Dermatomal scars, limb hypoplasia | | Parvovirus B19 (parvovirus_b19) | Severe fetal anaemia, hydrops | | [Zika virus (zika_virus)](https://durgical.com/en/conditions/zika-virus-infection/) | Severe microcephaly, subcortical calcifications, arthrogryposis | | [Listeria monocytogenes (listeria_monocytogenes)](https://durgical.com/en/conditions/neonatal-sepsis/) | Miscarriage, preterm birth, neonatal sepsis and meningitis | ## What it does to the embryo and fetus - At birth: growth restriction, microcephaly, hepatosplenomegaly, jaundice, petechiae or a 'blueberry muffin' rash. - Eyes: chorioretinitis (toxoplasma, CMV), cataracts (rubella), macular scars (Zika). - Ears: sensorineural deafness, mainly from CMV and rubella; it can appear months later. - Fetal death, miscarriage or hydrops (parvovirus B19, syphilis). ## Memory aid Toxo 'scatters' calcium all over the brain; CMV 'sticks' it around the ventricles. ## Test yourself Think of the answer, then tap the question to see it. ## Which congenital infection is the leading non-genetic cause of sensorineural deafness? Cytomegalovirus. ## Which triad suggests congenital toxoplasmosis? Chorioretinitis, hydrocephalus and diffuse intracranial calcifications. ## Which late findings make up the Hutchinson triad of congenital syphilis? Hutchinson teeth (notched, peg-shaped incisors), interstitial keratitis and sensorineural deafness. ## Why does parvovirus B19 cause fetal hydrops? It infects erythroid precursors and causes severe fetal anaemia, leading to heart failure and generalized oedema. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/embryology/torch-infections-what-each-agent-does-to-the-embryo-and-fetus/) ## See it in 3D The structures of Durgical's 3D anatomy where it is found. - [Retina](https://durgical.com/en/anatomy/retina/) - [Cochlea](https://durgical.com/en/anatomy/cochlea/) - [Lens](https://durgical.com/en/anatomy/lens/) - [Lateral ventricles](https://durgical.com/en/anatomy/lateral-ventricle/) - [Liver](https://durgical.com/en/anatomy/liver/) ## Related - [Congenital rubella syndrome](https://durgical.com/en/embryology/congenital-rubella-syndrome/) - [Congenital Zika syndrome](https://durgical.com/en/embryology/congenital-zika-syndrome/) - [Microcephaly](https://durgical.com/en/embryology/microcephaly/) - [Congenital hydrocephalus: aqueductal stenosis](https://durgical.com/en/embryology/congenital-hydrocephalus-aqueductal-stenosis/) - [Coloboma, congenital cataract and congenital glaucoma](https://durgical.com/en/embryology/coloboma-congenital-cataract-and-congenital-glaucoma/) - [Congenital hearing loss, microtia and preauricular pits](https://durgical.com/en/embryology/congenital-hearing-loss-microtia-and-preauricular-pits/) - [Placenta: structure, circulation and functions](https://durgical.com/en/embryology/placenta-structure-circulation-and-functions/) - [Principles of teratology: critical periods, dose and genotype](https://durgical.com/en/embryology/principles-of-teratology-critical-periods-dose-and-genotype/) ## Related conditions - [Congenital (TORCH) infections: syphilis, toxoplasmosis, CMV and Zika](https://durgical.com/en/conditions/congenital-infections-syphilis-toxoplasmosis-cmv-and-zika/) - [Syphilis](https://durgical.com/en/conditions/syphilis/) - [Varicella (chickenpox)](https://durgical.com/en/conditions/varicella/) - [Genital herpes (herpes simplex infection)](https://durgical.com/en/conditions/genital-herpes/) - [Hearing loss (conductive and sensorineural, including sudden hearing loss)](https://durgical.com/en/conditions/hearing-loss/) - [Cataract](https://durgical.com/en/conditions/cataract/) - [Zika virus infection](https://durgical.com/en/conditions/zika-virus-infection/) - [Neonatal sepsis](https://durgical.com/en/conditions/neonatal-sepsis/) ## Microorganisms - [Toxoplasma gondii](https://durgical.com/en/microbiology/toxoplasma-gondii/) - [Treponema pallidum](https://durgical.com/en/microbiology/treponema-pallidum/) - [Rubella virus](https://durgical.com/en/microbiology/rubella-virus/) - [Cytomegalovirus](https://durgical.com/en/microbiology/cytomegalovirus/) - [Herpes simplex virus 2](https://durgical.com/en/microbiology/herpes-simplex-virus-2/) - [Herpes simplex virus 1](https://durgical.com/en/microbiology/herpes-simplex-virus-1/) - [Varicella-zoster virus](https://durgical.com/en/microbiology/varicella-zoster-virus/) - [Zika virus](https://durgical.com/en/microbiology/zika-virus/) - [Parvovirus B19](https://durgical.com/en/microbiology/parvovirus-b19/) - [Listeria monocytogenes](https://durgical.com/en/microbiology/listeria-monocytogenes/) [← All of embryology](https://durgical.com/en/embryology/) Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given. Sources: [Embryology, Teratology TORCH](https://www.ncbi.nlm.nih.gov/books/NBK545148/) (StatPearls Publishing (NCBI Bookshelf), 2023); [CMV in Newborns](https://www.cdc.gov/cytomegalovirus/congenital-infection/index.html) (CDC, 2024); [Pregnancy and Rubella](https://www.cdc.gov/rubella/pregnancy/index.html) (CDC, 2024); [Congenital Zika Syndrome](https://archive.cdc.gov/www_cdc_gov/ncbddd/birthdefects/surveillancemanual/quick-reference-handbook/congenital-zika-syndrome.html) (CDC, NCBDDD (archived surveillance manual), 2020). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/embryology/torch-infections-what-each-agent-does-to-the-embryo-and-fetus/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/embryology/torch-infections-what-each-agent-does-to-the-embryo-and-fetus/