SAS 10: COMMON TERATOGENS

TERATOGEN

Any factor (chemical or physical) that adversely affects the fertilized ovum, embryo, or fetus.

Requirements for Optimal Fetal Health

Sound genes, Healthy intrauterine environment, Teratogen's strength.

Timing of the Teratogenic Insult

Before implantation: Zygote is either destroyed or unaffected; During organogenesis (1st trimester): Fetus is most vulnerable; 3rd trimester: Harm tends to decrease.

Other Influencing Factors

Teratogen's affinity for specific tissues.

Lead

Targets nervous tissue.

Thalidomide

Causes limb defects.

Tetracycline

Affects tooth enamel & bone.

Exceptions (affect fetus throughout pregnancy)

Syphilis, Toxoplasmosis.

TERATOGENIC MATERNAL INFECTIONS

May include STIs or systemic infections, can be viral, bacterial, or protozoan, often cause mild or flu-like symptoms in the mother but can lead to serious fetal or neonatal effects.

TORCH Infections

Teratogenic infections screened in pregnancy: T - Toxoplasmosis, O - Other (Syphilis, Hepatitis B, HIV), R - Rubella, C - Cytomegalovirus, H - Herpes Simplex Virus.

TORCH Screen

Immunologic tests for both the pregnant woman and the newborn.

Purpose of TORCH Screen

Identify fetal risk (mother), Detect antibodies to teratogens (newborn).

Results of TORCH Screen

Negative: Normal (no infection); Positive IgM: Recent or current infection; Positive IgG: Maternal antibodies crossed the placenta.

TOXOPLASMOSIS

A fetus may contact toxoplasmosis through the placental connection with its infected mother.

Toxoplasmosis Infection Sources

Improper handling of cat litter, Handling or ingesting contaminated meat.

Toxoplasmosis in Infants

Can cause serious congenital issues, especially if acquired during pregnancy: CNS damage, Hydrocephalus, Microcephaly, Intracerebral calcification, Retinal deformities.

Medications for Toxoplasmosis

Treatment focuses on reducing the severity of symptoms, though some may not fully prevent deformities.

Sulfonamides

May increase bilirubin in newborns, May not prevent deformities.

Pyrimethamine

An antiprotozoal and anti-folic acid drug.

Folic Acid

Supplement to offset folic acid inhibition by pyrimethamine.

Spiramycin

Experimental use during pregnancy.

Important Notes on Immunization

Given if fetus is not yet affected.

Prevention Tips for Toxoplasmosis

Reduce risk of maternal infection during pregnancy: No need to remove a healthy cat from the home, Do not adopt new cats during pregnancy, Avoid undercooked meat, Do not change cat litter or work in contaminated soil; If necessary, use gloves.

RUBELLA

Rubella (German measles) is a viral infection that causes mild illness in the mother but can result in severe congenital defects if transmitted to the fetus during pregnancy.

Maternal Symptoms

Mild rash and mild systemic illness.

Congenital Rubella Syndrome (CRS)

Fetal complications due to maternal rubella infection.

Deafness

A potential fetal complication of Congenital Rubella Syndrome.

Mental & motor challenges

A potential fetal complication of Congenital Rubella Syndrome.

Cataracts

A potential fetal complication of Congenital Rubella Syndrome.

Cardiac defects

A potential fetal complication of Congenital Rubella Syndrome, including PDA and pulmonary stenosis.

PDA (Patent Ductus Arteriosus)

A type of cardiac defect associated with Congenital Rubella Syndrome.

Pulmonary stenosis

A type of cardiac defect associated with Congenital Rubella Syndrome.

Restricted intrauterine growth (SGA)

A potential fetal complication of Congenital Rubella Syndrome.

Thrombocytopenic purpura

A potential fetal complication of Congenital Rubella Syndrome.

Dental & facial clefts

A potential fetal complication of Congenital Rubella Syndrome.

Rubella titer

Test done at the 1st prenatal visit to determine immunity to rubella.

> 1:8

Indicates immune to rubella.

< 1:8

Indicates susceptible to rubella infection.

A high or rising titer

Suggests recent rubella infection.

Rubella vaccine

Contraindicated during pregnancy.

Immunization after delivery

Check titer and immunize if the mother is not immune.

Avoid pregnancy for at least 3 months

Recommended after rubella vaccination.

Reinfection

Possible; avoid contact with children who have rashes.

Cytomegalovirus (CMV)

A member of the herpes virus family spread through droplet infection.

Fetal Symptoms of CMV Infection

Includes neurological damage, eye damage, deafness, chronic liver disease, and blueberry muffin lesions.

Detection of CMV antibodies

From mother's blood or infant's blood serum.

No specific treatment or vaccine

Available for CMV infection.

Herpes Simplex Virus (HSV)

Also known as Genital Herpes Infection, caused by Herpes Simplex Virus Type 2.

1st Episode Infection

Can cross the placenta to the fetus.

1st Trimester Infection

May lead to severe congenital anomalies or spontaneous miscarriage.

2nd or 3rd Trimester Infection

Higher risk of premature birth, IUGR, and persistent neonatal infection.

Existing antibodies

May protect the fetus from transplacental spread if the woman had HSV-1 earlier.

Active genital lesions at delivery

May infect the newborn through direct contact.

Cesarean section (CS)

Recommended if active genital lesions are present during labor.

IV Acyclovir

A treatment option for HSV.

Oral Acyclovir (Zovirax)

A treatment option for HSV.

Syphilis

Caused by the bacterium Treponema pallidum.

Transmission to Fetus

Around 16th-18th week, the cytotrophoblastic layer of chorionic villi atrophies, allowing the bacteria to cross the placenta.

Early Treatment

If detected and treated early (1st trimester) with benzathine penicillin, fetal infection is rare.

Risks if Untreated Beyond 18 Weeks

Risks include deafness, cognitive challenges, osteochondritis, and fetal death.

Diagnosis & Screening

Serologic screening using VDRL (Venereal Disease Research Laboratory) and RPR (Rapid Plasma Reagin).

Screening Timing

Screen at first prenatal visit and again near term if there's a risk of exposure.

Infant Testing Post-Treatment

In treated mothers, infant may still test positive for up to 3 months due to passive maternal antibodies.

Congenital Syphilis in the Newborn (NB)

Congenital anomalies, extreme rhinitis ('Sniffles'), syphilitic rash, Hutchinson teeth (oddly shaped, notched upper central incisors).

Early Prenatal Screening

Perform VDRL or RPR serologic tests at the first prenatal visit.

Repeat Testing

Repeat testing close to term if the mother is high-risk or has ongoing exposure.

Timely Treatment

If syphilis is detected, administer benzathine penicillin as early as possible—ideally in the first trimester.

Effect of Early Treatment

Early treatment significantly reduces the risk of fetal complications.

Avoiding Exposure

Educate on safe sexual practices (e.g., consistent condom use) and encourage partner testing and treatment to prevent reinfection.

Follow-up and Monitoring

Monitor maternal titers to assess treatment effectiveness and ultrasound monitoring may be done to check for signs of fetal infection in untreated or late-diagnosed cases.

Postpartum Immunization

Although there's no vaccine for syphilis, postpartum care should include repeat screening for untreated or high-risk women.

Zika Virus

Spread primarily through bites from the Aedes aegypti mosquito.

Zika Transmission to Fetus

Can be passed from a pregnant woman to her fetus.

Zika Transmission Methods

Also transmitted through unprotected sex with an infected person and via body fluids such as blood and semen.

Effects of Zika on the Fetus

Zika infection during pregnancy can cause microcephaly (small head & underdeveloped brain) and other severe fetal brain defects.

Symptoms in Infected Individuals

First symptoms may appear 3 to 12 days after exposure and can include fever, rash, joint pain, and conjunctivitis (red eyes).

Prevention of Zika

Avoid travel to areas with known Zika risk.

Safe Sex Practices for Zika

Use condoms or avoid sexual contact with anyone who recently traveled to Zika affected areas or has symptoms of Zika.

Mosquito Protection

Use insect repellent and stay in places with screens or air conditioning.

Breastfeeding with Zika

CDC encourages breastfeeding, even if the mother has or had Zika infection.

Testing During Pregnancy for Zika

Pregnant women should be tested if they show Zika symptoms or ultrasound detects fetal abnormalities suggestive of infection.