What is a teratogen

A teratogen is any agent that causes harmful fetal effect or birth defect following fetal exposure during pregnancy. Teratogens are usually discovered after an increased prevalence of a particular birth defect. For example, in the early 1960’s, a drug known as thalidomide was used to treat morning sickness. Exposure of the fetus during this early stage of development resulted in cases of phocomelia, a congenital malformation in which the hands and feet are attached to abbreviated arms and legs.

Recognized human teratogens:

  • Drugs:
    • anticonvulsants
    • methimazole
    • retinoic acid (Accutane)
    • misoprostol
  • Heavy metals
    • lead
    • mercury
  • Radiation
    • cancer therapy
    • non-diagnostic X-rays
  • Maternal conditions
    • alcohol use/abuse
    • cigarette
    • smoking
    • diabetes
    • hypotension
    • hyperthermia
    • phenylketonuria (PKU)
  • Intrauterine infections
    • toxoplasmosis
    • rubella
    • cytomegalovirus
    • herpes simplex
    • syphilis
    • varicella
    • zika
  • Procedures
    • amniocentesis
    • CVS (chorionic villus sampling)
    • Intracytoplasmic Sperm Injection (ICSI)
    • Dilation and curettage (D&C)

Teratogens can also be found at home or the workplace. The effect is related to type of agent, dose and duration and time of exposure. The first half of pregnancy is the most vulnerable. Teratogenic agents include infectious agents (rubella, cytomegalovirus, varicella, herpes simplex, toxoplasma, syphilis, etc.); physical agents (ionizing agents, hyperthermia); maternal health factors (diabetes, maternal PKU); environmental chemicals (organic mercury compounds, polychlorinated biphenyl or PCB, herbicides and industrial solvents); and drugs (prescription, over- the-counter, or recreational). In general, if medication is required, the lowest dose possible should be used and combination drug therapies and first trimester exposures should be avoided.

The types or severity of abnormalities caused by a teratogenic agent is also dependent on the genetic susceptibilities carried by the mother and fetus. For example, variation in maternal metabolism of a particular drug will determine what metabolites the fetus is exposed to and the duration of exposure. The genetic susceptibility of the fetus to a particular teratogenic agent will also have an effect on the final outcome.

Teratogen birth defects:

  • Spontaneous abortion
  • Growth restriction
  • Pattern of major and minor anomalies
  • Major malformations
  • Stillbirth
  • Abruptio placenta
  • Cognitive dysfunction
  • Altered social behavior
  • Cancer

Two of the leading preventable causes of birth defects and developmental disabilities are alcohol and smoking. Alcohol use in pregnancy has significant effects on the fetus and the baby. Alcohol can pass from the mother’s blood stream through the placenta to the fetus. Since alcohol is broken down more slowly in a fetus than in an adult, alcohol levels tend to remain high and stay in the baby’s body longer. Birth defects associated with prenatal exposure to alcohol can occur in the first three to eight weeks of pregnancy, before a woman even knows that she is pregnant.

Fetal alcohol syndrome is a group of abnormalities in babies born to mothers who consume alcohol during pregnancy. It is the most common known non-genetic (non-inherited) cause of mental retardation in the U.S.

In 2001, the estimated prevalence of smoking during pregnancy for all U.S. women was 11.4%, ranging from 3.9% in DC to 26.2% in West Virginia. Smoking nearly doubles a woman’s risk of having a low birth-weight baby as a result of poor growth before birth, preterm delivery or a combination of both. Premature and low birth-weight babies face an increased risk of serious health problems during the newborn period, chronic lifelong disabilities (e.g., cerebral palsy, mental retardation) and possibly death. More recent studies have suggested a possible link between prenatal smoking exposure and behavioral problems in later childhood and adolescence.

In addition, almost three percent of pregnant women use illicit drugs such as marijuana, cocaine, Ecstasy and other amphetamines, and heroin. These drugs can cause low birth-weight, withdrawal symptoms, birth defects, or learning or behavioral problems.

Alcohol teratogen

Fetal Alcohol Spectrum Disorder or FASD is a condition in a child that results when alcohol is consumed while pregnant. Alcohol in the mother’s blood passes to the baby through the umbilical cord. There is no known safe amount of alcohol during pregnancy or when trying to get pregnant. There is also no safe time to drink during pregnancy. Alcohol can cause problems for a developing baby throughout pregnancy, including before a woman knows she’s pregnant. All types of alcohol are equally harmful, including all wines and beer. To the fetus, alcohol is a behavioral teratogen. A behavioral teratogen is a substance that also causes behavioral problems. Fetal alcohol syndrome causes brain damage and growth problems. Although prenatal alcohol exposure presents a physical risk to the baby, it is the behavior that causes the family and the individual the most problems. It is important to remember that brain equals behavior. Many parts of the brain can be affected as can a variety of organs, depending on the time in pregnancy and amount of alcohol consumed and fetal alcohol syndrome are not reversible.

To prevent fetal alcohol spectrum disorders (FASDs), a woman should not drink alcohol while she is pregnant, or if there is a chance she might be pregnant.

There is no amount of alcohol that’s known to be safe to consume during pregnancy. If you drink during pregnancy, you place your baby at risk of fetal alcohol syndrome.

If you suspect your child has fetal alcohol syndrome, talk to your doctor as soon as possible. Early diagnosis may help to reduce problems such as learning difficulties and behavioral issues.

The parts of the brain most commonly affected by alcohol are:

  • The corpus callosum
  • Hippocampus
  • Hypothalamus
  • Basal Ganglia
  • Amygdala
  • Frontal Lobes

The most common physiological problems are:

  • Heart
  • Kidneys
  • Hearing [otitis media]
  • Vision

Fetal Alcohol Spectrum Disorder Key Facts:

  • Drinking alcohol during pregnancy can cause lifelong physical, behavioral, and intellectual disabilities.
  • Women who are pregnant or who might be pregnant should not drink alcohol, including women who are trying to get pregnant.
  • All types of alcohol are equally harmful, including all wines and beer.
  • Fetal Alcohol Spectrum Disorders last a lifetime. There is no cure for fetal alcohol spectrum disorders. But early intervention can improve a child’s development.

In the United States, it has been estimated that each individual with fetal alcohol spectrum disorder will cost the government $2.9 million over his or her lifetime 1). In the report on The Financial Impact of fetal alcohol spectrum disorder, the SAMHSA FASD Center for Excellence stated that the United States has an annual birth rate of just fewer than 4 million 2), with 40,000 of those births alcohol affected. Extrapolated to Australia’s population, this rate suggests that each year a minimum of 3,000 babies will be born prenatally exposed to alcohol and it will often only be at puberty that the true extent of their disability will become clear.

Prevention Tips

  • Women who are pregnant or who might be pregnant should not drink alcohol. This includes women who are trying to get pregnant and women who are at risk of becoming pregnant because they do not use effective contraception (birth control).
  • There is no known safe amount of alcohol use during pregnancy or when trying to get pregnant.
  • The best advice is to stop drinking alcohol when you start trying to get pregnant.
  • It is never too late to stop drinking. Because brain growth takes place throughout pregnancy, the sooner you stop drinking, the safer it will be for you and your baby.

Types of fetal alcohol spectrum disorders

Different terms are used to describe fetal alcohol spectrum disorders (FASDs), depending on the type of symptoms.

  • Fetal Alcohol Syndrome (FAS): Fetal Alcohol Syndrome represents the most involved end of the fetal alcohol spectrum disorder spectrum. Fetal death is the most extreme outcome from drinking alcohol during pregnancy. People with Fetal Alcohol Syndrome might have abnormal facial features, growth problems, and central nervous system (brain and spinal cord) problems. People with fetal alcohol syndrome can have problems with learning, memory, attention span, communication, vision, or hearing. They might have a mix of these problems. People with fetal alcohol syndrome often have a hard time in school and trouble getting along with others.
  • Alcohol-Related Neurodevelopmental Disorder (ARND): People with alcohol-related neurodevelopmental disorder might have intellectual disabilities and problems with behavior and learning. They might do poorly in school and have difficulties with math, memory, attention, judgment, and poor impulse control.
  • Alcohol-Related Birth Defects (ARBD): People with alcohol-related birth defects might have problems with the heart, kidneys, or bones or with hearing. They might have a mix of these.
  • Neurobehavioral Disorder Associated with Prenatal Alcohol Exposure (ND-PAE): Neurobehavioral Disorder Associated with Prenatal Alcohol Exposure was first included as a recognized condition in the Diagnostic and Statistical Manual 5 (DSM 5) of the American Psychiatric Association (APA) in 2013. A child or youth with neurobehavioral disorder associated with prenatal alcohol exposure will have problems in three areas: (1) thinking and memory, where the child may have trouble planning or may forget material he or she has already learned, (2) behavior problems, such as severe tantrums, mood issues (for example, irritability), and difficulty shifting attention from one task to another, and (3) trouble with day-to-day living, which can include problems with bathing, dressing for the weather, and playing with other children. In addition, to be diagnosed with neurobehavioral disorder associated with prenatal alcohol exposure, the mother of the child must have consumed more than minimal levels of alcohol before the child’s birth, which APA defines as more than 13 alcoholic drinks per month of pregnancy (that is, any 30-day period of pregnancy) or more than 2 alcoholic drinks in one sitting.

Fetal alcohol spectrum disorder signs and symptoms

Fetal alcohol spectrum disorders (FASDs) refer to the whole range of effects that can happen to a person whose mother drank alcohol during pregnancy. These conditions can affect each person in different ways, and can range from mild to severe.

Not everyone will have all the signs and symptoms outlined below. Effects will depend on the time of pregnancy during which alcohol was consumed, the amount that was consumed, the nutrition of the mother, other drug use, the general health of the mother and researchers have now found that epigenetics also plays a part in the severity of the fetal alcohol spectrum disorders (FASDs) 3).

People with fetal alcohol spectrum disorder may have trouble setting personal boundaries and observing other people’s boundaries. They often have emotional problems, can be impulsive, may not be able to sustain relationships, and often cannot anticipate consequences. They have difficulty paying attention, have poor organizational skills and have trouble completing tasks and managing time.

A person with an fetal alcohol spectrum disorder (FASD) might have:

  • Abnormal facial features, such as a smooth ridge between the nose and upper lip (this ridge is called the philtrum)
  • Small head size
  • Shorter-than-average height
  • Low body weight
  • Poor coordination
  • Hyperactive behavior
  • Difficulty with attention
  • Poor memory
  • Difficulty in school (especially with math)
  • Learning disabilities
  • Speech and language delays
  • Intellectual disability or low IQ
  • Poor reasoning and judgment skills
  • Sleep and sucking problems as a baby
  • Vision or hearing problems
  • Problems with the heart, kidneys, or bones

Other possible problems include:

Early Development

  • Failure to thrive
  • Tremors or jitters
  • Seizures
  • Feeding problems in infancy
  • Sleeping problems
  • Vision and/or hearing problems
  • Difficulty with toilet training, wetting or soiling
  • Problems with personal hygiene
  • Difficulty with the onset of puberty
  • Problems with sexual functioning

Childhood Appearance

  • Shorter or thinner than other children the same age
  • Eyes may be wide-spaced, smaller than normal, slanted, droopy eyelids
  • Lips may be long and/or there may be a smooth space between the upper lip and nose (philtrum)
  • Thin vermilion border (upper lip)

Communication and Speech

  • Talks excessively and quickly
  • Interrupts
  • Not apropos conversational subjects
  • Opinionated
  • Speaks indistinctly
  • Makes ‘off the wall’ comments
  • Repeats phrases/words frequently, almost as though ‘acting’

Memory, Learning and Information Processing

  • Poor/inconsistent memory
  • Slow to learn new skills
  • Does not seem to learn from mistakes
  • Has difficulty linking cause and consequence
  • Experiences slow information processing [possibly related to Central Auditory Processing Disorder]

Behavior Regulation

  • Poor anger management
  • Fearless in the face of danger
  • Mood swings
  • Impulsive and compulsive
  • Perseverative
  • Inattentive often diagnosed or mis-diagnosed as ADHD
  • Unusual activity level [high or low]
  • Illogical lying
  • Illogical stealing
  • Unusual reactivity to sound, touch, light
  • Fidgety, cannot sit still

Abstract Thinking and Judgment

  • Poor judgment
  • Unable to plan and execute
  • Functions poorly without assistance
  • Concrete, black or white thinking – does not understand idiom


  • Needs help organizing daily tasks
  • Cannot manage time or money
  • Misses appointments
  • Has difficulty with multi-step instructions

Spatial Skills and Spatial Memory

  • Gets lost easily, has difficulty navigating from point A to point B
  • Poor memory for sequences and dates

Motor Skills

  • Poor or delayed motor skills
  • Overly active
  • Poor balance, accident prone & clumsy

Social Skills and Adaptive Behavior

  • Poor social or adaptive skills
  • Overly-friendly
  • Attention-seeking
  • Behaves notably younger than chronological age
  • Few close friends, easily led or manipulated by others
  • Laughs inappropriately
  • Poor social or sexual boundaries

Academic and Work Performance

  • Gives impression of being more capable than he/she actually is
  • Tries hard and wants to please, but end result is often disappointing
  • Has trouble completing tasks or school drop-out
  • Has problems with school or job attendance
  • Poor work history

Fetal alcohol spectrum disorder diagnosis

Deciding if a child has fetal alcohol syndrome takes several steps. There is no one test to diagnose fetal alcohol syndrome, and many other disorders can have similar symptoms. Following is an overview of the diagnostic guidelines for fetal alcohol syndrome.

These criteria have been simplified for a general audience. They are listed here for information purposes and should be used only by trained health care professionals to diagnose or treat fetal alcohol syndrome.

Healthcare professionals look for the following signs and symptoms when diagnosing fetal alcohol syndrome:

  • Abnormal facial features
    • A person with fetal alcohol syndrome has three distinct facial features:
      • Smooth ridge between the nose and upper lip (smooth philtrum)
      • Thin upper lip
      • Short distance between the inner and outer corners of the eyes, giving the eyes a wide-spaced appearance.
  • Growth problems
    • Children with fetal alcohol syndrome have height, weight, or both that are lower than normal (at or below the 10th percentile). These growth issues might occur even before birth. For some children with fetal alcohol syndrome, growth problems resolve themselves early in life.
  • Central nervous system problems
    • The central nervous system is made up of the brain and spinal cord. It controls all the workings of the body. When something goes wrong with a part of the nervous system, a person can have trouble moving, speaking, or learning. He or she can also have problems with memory, senses, or social skills. There are three categories of central nervous system problems:
  • Structural -fetal alcohol syndrome can cause differences in the structure of the brain. Signs of structural differences are:
    • Smaller-than-normal head size for the person’s overall height and weight (at or below the 10th percentile).
    • Significant changes in the structure of the brain as seen on brain scans such as MRIs or CT scans.
  • Neurologic
    • There are problems with the nervous system that cannot be linked to another cause. Examples include poor coordination, poor muscle control, and problems with sucking as a baby.
  • Functional
    • The person’s ability to function is well below what’s expected for his or her age, schooling, or circumstances. To be diagnosed with fetal alcohol syndrome, a person must have:
  • Cognitive deficits (e.g., low IQ), or significant developmental delay in children who are too young for an IQ assessment.
  • OR
  • Problems in at least three of the following areas:
    1. Cognitive deficits (e.g., low IQ) or developmental delays. Examples include specific learning disabilities (especially math), poor grades in school, performance differences between verbal and nonverbal skills, and slowed movements or reactions.
    2. Executive functioning deficits. These deficits involve the thinking processes that help a person manage life tasks. Such deficits include poor organization and planning, lack of inhibition, difficulty grasping cause and effect, difficulty following multistep directions, difficulty doing things in a new way or thinking of things in a new way, poor judgment, and inability to apply knowledge to new situations.
    3. Motor functioning delays. These delays affect how a person controls his or her muscles. Examples include delay in walking (gross motor skills), difficulty writing or drawing (fine motor skills), clumsiness, balance problems, tremors, difficulty coordinating hands and fingers (dexterity), and poor sucking in babies.
    4. Attention problems or hyperactivity. A child with these problems might be described as “busy,” overly active, inattentive, easily distracted, or having difficulty calming down, completing tasks, or moving from one activity to the next. Parents might report that their child’s attention changes from day to day (e.g., “on” and “off” days).
    5. Problems with social skills. A child with social skills problems might lack a fear of strangers, be easily taken advantage of, prefer younger friends, be immature, show inappropriate sexual behaviors, and have trouble understanding how others feel.
    6. Other problems. Other problems can include sensitivity to taste or touch, difficulty reading facial expression, and difficulty responding appropriately to common parenting practices (e.g., not understanding cause-and-effect discipline)
  • Mother’s Alcohol Use during Pregnancy
    • Confirmed alcohol use during pregnancy can strengthen the case for FAS diagnosis. Confirmed absence of alcohol exposure would rule out the FAS diagnosis. It’s helpful to know whether or not the person’s mother drank alcohol during pregnancy. But confirmed alcohol use during pregnancy is not needed if the child meets the other criteria.

Summary: Criteria for fetal alcohol syndrome diagnosis

A diagnosis of fetal alcohol syndrome requires the presence of all three of the following findings:

  • All three facial features
  • Growth deficits
  • Central nervous system problems. A person could meet the central nervous system criteria for fetal alcohol syndrome diagnosis if there is a problem with the brain structure, even if there are no signs of functional problems.

Fetal alcohol spectrum disorder treatment

Fetal alcohol spectrum disorders (FASDs) last a lifetime. There is no cure for fetal alcohol spectrum disorders, but research shows that early intervention treatment services can improve a child’s development.

There are many types of treatment options, including medication to help with some symptoms, behavior and education therapy, parent training, and other alternative approaches. No one treatment is right for every child. Good treatment plans will include close monitoring, follow-ups, and changes as needed along the way.

Also, “protective factors” can help reduce the effects of fetal alcohol spectrum disorders (FASDs) and help people with these conditions reach their full potential 4).

Protective factors include:

  • Diagnosis before 6 years of age
  • Loving, nurturing, and stable home environment during the school years
  • Absence of violence
  • Involvement in special education and social services.

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