Maternal Exposures

1. Physical Agents
2. Infectious Agents
3. Maternal Diseases

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1. PHYSICAL AGENTS:

IONIZING RADIATION

• Acute large-dose radiation has no effect nor is it lethal to the embryo during the pre-implantation stage. During the period of embryogenesis it causes microcephaly mental and growth retardation.

• The risk is greatest at 8-15 weeks of gestation.

• Continuous chronic low dose exposure of less than 5rad has no adverse effects.

• There is an association between in utero exposure to diagnostic radiation and childhood leukemia.

• Video Display Terminals (VDT) has no adverse reproductive outcomes.

HYPERTHERMIA, PYREXIA

• May cause neural tube defects in the fetus.

• May cause abortions, intrauterine death or preterm labor.

ORGANIC MERCURY- METHYL MERCURY

• Maternal poisoning causes fetal neurologic damage with psychomotor retardation, seizures, cerebral palsy, blindness and deafness.

• Low-level methyl mercury exposure may cause chromosomal abnormalities in the embryo; and has been shown to be lethal in animals at high doses causing structural malformations such as exencephaly and limb deformities.

ELEMENTAL MERCURY (VAPOR)

• Chronic exposure to high doses (more than 0.01 mg/m3) can cause cranial defects and fetal resorption in animals.

• Limited human data available, but possible association present between chronic exposure to high doses with abortions and brain damage to the fetus.

LEAD

• Lead concentration in the blood should not exceed 25meg/dL in women of reproductive age and should be less than 10 mg/dL in pregnant women, to ensure no adverse effects to the fetus. Women should not work in areas where lead concentration in the air reaches 50 meg/cm3.

• Exposure to high levels can cause embryotoxicity, growth and mental retardation, abortions, premature rupture of membranes, preterm deliveries, neurologic impairment (attention deficit disorders, hearing deficit, learning disabilities) and short stature.

• Prenatal lead exposure may cause impaired mental development.

• Mothers exposed to high lead levels should avoid breast feeding.
  
   

ORGANIC SOLVENTS INCLUDING TOLUENE

• Maternal solvent abuse by sniffing may cause embryopathy similar to fetal alcohol syndrome.

• Occupational exposure to organic solvent may cause spontaneous abortions.

ANESTHETIC GASES

• Women chronically exposed to anesthetic gases in the 1st trimester are at increased risk to spontaneous abortions.

• Maternal exposure to anesthetic gases increases the risk of congenital anomalies (Spina bifida).

• Chronic exposure to unscavenged nitrous oxide may reduce fertility and increase the risk of spontaneous abortion.

SMOKING

• Associated with:

  • Small for date babies

  • Prematurity

  • Increase in rate of spontaneous abortion and increase in perinatal mortality due to an increased risk of abruption, placenta previa and premature rupture of membranes.

• Passive smoking is also associated with low birth weight at term.

• Associated with sudden infant death syndrome.

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2. INFECTIOUS AGENTS:

RUBEOLA (MEASLES)

• Not teratogenic.

• May cause placental damage.

• With subsequent stillbirth may increase in perinatal mortality.

• As a febrile illness, it may induce uterine contractions causing preterm deliveries.

• Mothers with active disease may deliver the newborn with severe infection.

• Suggested association between in utero exposure to measles and postnatal development of Crohn’s disease.

RUBELLA (GERMAN MEASLES)

• Maternal infection during pregnancy may result in:

  • Spontaneous abortion

  • Congenital rubella syndrome:

Eye defects (cataract, retinopathy, microphthalmia, glaucoma), heart defects, ear defects leading to deafness, fetal and neonatal growth retardation, psychomoter retardation, hepato-spleno-megaly, thrombocytopenia, meningoencephalitis, microcephaly, brain calcification, hepatitis, myocardial necrosis, radiolucency of long bones.
 

• Late onset features of the syndrome include:

  • Chronic rubella - like rash

  • Interstitial pneumonitis

  • Chronic diarrhea

  • Hypogammaglobulinemia

  • Diabetes mellitus

  • Progressive central nervous system impairment.

• Late sequelae of in utero rubella infection:

  • Deafness

  • Diabetes

  • Subacute sclerosing panencephalitis

CYTOMEGALOVIRUS (CMV)

• Maternal infection may cause congenital infection with the following features:
  Hepatosplenomegaly, thrombocytopenia with petechiae, purpura, hepatitis, pneumonitis, chorioretinitis, microcephaly, optic atrophy, microphthalmia, intrauterine growth retardation, intracranial calcification with mental retardation, neonatal death if severe infection.

• Late sequelae:
  Mental retardation, auditory deficiency and deafness, visual difficulties (optic atrophy, cataract, microphthalmia, optic neuritis, chorioretinitis).

PARVO VIRUS B19 INFECTION

• Maternal infection during pregnancy may result in

  • Fetal loss

  • Still birth

  • Fetal hydrops

  • Intrauterine growth retardation

TOXOPLASMOSIS
 

•  Maternal infection during pregnancy may result in:

  • Abortion

  • Stillbirth or neonatal death

  • Congenital infection:
    Chorioretinitis, hydro cephalus, intracranial calcification, hydrops fetalis, hepatosplenomegaly

• Late sequelae include:
  Mental retardation, motor defects, spasticity, seizures, hearing and visual impairment.

VARICELLA (CHICKENPOX)

• Primary maternal infection in pregnancy can be associated with preterm delivery.

• Congenital varicella syndrome may occur with maternal infection before 20 weeks gestation

• Features of congenital varicella syndrome are:

  • Skin scarring, eye defects (microphthalmia, chorioretinitis, cataract), hypoplasia of the limbs, neurological abnormalities (microcephaly, cortical atrophy, mental retardation, dysfunction of bowel and bladder sphincters), hydrops fetalis, hyperechogenic foci in the liver, polyhydramnios, low birth weight.

• Neonatal varicella can occur.

• Infection occurring one to four weeks before delivery manifests as pneumonitis hepatitis and disseminated intravascular coagulation (DIC).

• In utero exposure to varicella may result in herpes zoster in infancy.

GENITAL HERPES

• Abortion may occur if maternal infection occurs before 20 weeks of gestation.

• Preterm delivery may occur if maternal infection occurs after 20 weeks of gestation.

• Fetal infection may occur causing microcephaly, microphthalmcia, hydranencephaly, skin lesions and scars at birth.

• Neonatal infection during vaginal delivery if the patient has active genital herpes.

• Features of neonatal infection:

  • Disseminated disease: lethargy, irritability, apnea, seizures, coagulopathy, cardio vascular compromise, liver involvement, death, Involvement of adrenal glands, larynx, trachea, lungs, esophagus, stomach, intestine spleen, oral and ocular lesions, encephalitis.

  • Central nervous system infection with encephalitis, seizures.

  • Local infection of the skin, mouth, eyes and pneumonia.

HIV
Can cause:

• Preterm deliveries.

• Low birth weight infants

• HIV embryo pathy- growth

• Retardation, craniofacial abnormalities microcephaly.

• Fetal infection.
   

SYPHILIS
May cause

• Still births.

• Preterm labor.

• Growth retardation.

• Fetal hydrops.

• Congenital syphilis.

• Neonatal infection.

Early congenital syphilis manifested as:

• Asymptomatic at birth

• Meningeal signs, lacrimation as a result of iritis, Nasal discharge, sore throat-pharynx, generalized arthralgia, splinting of arms and legs, osteochondritis, periostitis.

• Generalized adenopathy, hepatosplenomegaly, anemia, purpura, jaundice, edema, hypoalbuminemia.

• Maculopapular, papular, bullous eruption.

Late congenital syphilis:
Hutchinson’s teeth, mulberry mollars interstitial keratitis, eighth nerve deafness, saddle nose saber shin and cardio vascular lesions.

HEPATITIS B
May cause:

• Low birth weight infants.

• Infection of the neonate and possible late sequelae of chronic HBV infection, hepatic cirrhosis and hepatocellular carcinoma.

LISTERIOSIS
May cause:

• Abortion.

• Fetal and neonatal infection.
   

Early onset neonatal infection manifested as sepsis.

Late onset neonatal infection manifested mainly as meningitis.

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3. MATERNAL DISEASES:

DIABETES
Uncontrolled diabetes in preguancy may cause

• Abortions.

• Still births.

• Macrosomia and traumatic delivery.
  o Neonatal hypoglycemia, hypocalcemia, hyper-viscosity, hyaline membrane disease, apnea.

• Preterm delivery.

• Congenital abnormalities including cardio vascular, central nervous system, genito-urinary, gastro intestinal and skeletal (sacral agenesis).

• Intrauterine growth retardation in diabetic vasculopathy.

CARDIAC DISEASE
Cardiac disease in the pregnant women may cause

• Fetal death.

• Preterm delivery.

• Fetal growth retardation.

Increased risk of fetal congenital cardio vascular anomalies if the mother has congenital heart disease (risk is 4.5%).
 

EPILEPSY

• Epilepsy doubles the risk of fetal anomalies and the risk of inheritance of epilepsy.

• If only one parent has evidence of epilepsy the risk in the child is 4% (above that of general population), and the risk increases if both parents or a sibling are epileptic.

PRE-ECLAMPSIA
May cause:

• Fetal growth retardation.

• Fetal hypoxaemia with abnormal fetal doppler wave forms.

CHRONIC RENAL DISEASES
Chronic renal failure in pregnant women may cause:

• Small for date.

• Preterm delivery.

• Still births and neonatal deaths.

THYROID DISEASES

• Hyperthyroidism may cause:

  • Abortions.

  • Fetal thyrotoxicosis, goiter associated with the presence of thyroid stimulating immuno globulins which cross the placenta in patients with Graves disease persistent fetal tachycardia may occur with growth retardation.

  • Congenital anomalies, chromosomal defects.

   

• Hypothyroidism
  Women with hypothyroidism have a greater risk of:

  • Abortions.

  • Still births.

  • Prematurity.

  Untreated hypothyroidism may cause intellectual impairment of the newborn.

PHENYLKETONURIA
Women with phenylketonuria are at higher risk of spontaneous abortions, microcephaly and mental retardation.

SYSTEMIC LUPUS ERYTHEMATOSIS (SLE)
Women with SLE have a greater risk of:

• Abortions.

• Prematurity.

• Intrauterine death.

Neonatal lupus erythematosus features neonatal discoid lupus and severe systemic disease:

Hepatosplenomegaly, anemia, thrombocytopenia, skin lesions, congenital complete heart block; and in some cases neonatal death.

REFERENCES:

D K Edmonds. Deuhurst's Text Book of Obstetrics and Gynaecology for Postgraduates. 6th ed. Blackwell Science Ltd,1999.

S G Gabbe, J R Niebyl and J L Simpson. Obstetrics: Normal and Problem Pregnancies, 3rd ed. Churchill Livingstone, 1996.

L Impey. Obstetrics and Gynaecology, Blackwell Science, 1999.

Cunningham MacDonald, Gant leveno Gilstrap, Williams Obstetrics, 19th ed.  Prentice-Hall International Inc.

J Studd. Progress in Obstetrics and Gynaecology, volume 14, Churchill Livingstone, 2000.