What is the relationship between birth defects and drug use?

Drugs as Teratogens

Teratogens (teratogenic substances) are environmental substances that cause birth (or developmental) defects. Thousands of teratogenic substances exist, and a large number of them are drugs, including over-the-counter (OTC) drugs, prescription drugs, and illegal drugs of abuse.

Nearly all teratogens are most detrimental during the embryonic period (the second to eighth week of pregnancy). It is during this period in which organs form. Exposure to teratogenic substances may interfere with this normal organ formation. While drugs that are taken beyond the eighth week of pregnancy are not likely to cause actual birth defects, they may interfere with normal functioning of organs or may interfere with normal growth, causing intrauterine growth retardation. Drugs, like most other teratogens, affect the fetus when they cross the placenta along with oxygen and nutrients. Aspirin is one of the OTC drugs that is teratogenic, potentially causing bleeding in the pregnant woman and the fetus.

The use of prescription drugs may be necessitated because of a medical condition in the pregnant woman. If this is the case, it is essential for the medical professional to prescribe a drug that is not teratogenic or one that is unlikely to harm the fetus. One formerly common prescription drug, the broad-spectrum antibiotic tetracycline, caused discoloration of primary and secondary teeth in utero. Today, another broad-spectrum antibiotic is used to treat infection, decreasing the likelihood of a resultant birth defect.

Generally, when speaking of birth defects and drug use, one more commonly attributes defects to tobacco (smoking), alcohol, marijuana, stimulants, sedatives, addictive substances (like heroin or cocaine), and hallucinogens, most of which are teratogenic. Smoking tends to cause heart defects and intrauterine growth retardation. Alcohol exposure most typically causes fetal alcohol syndrome. This condition generally involves growth retardation and other physical and cognitive problems. No definite evidence exists about the teratogenic effects of marijuana, although the drug has been implicated in cases of small head circumference, neurological problems, and learning deficiencies. Investigations are ongoing into the effects of marijuana on prenatal development, especially because marijuana is the single most common illicit drug used by pregnant women.

Stimulants (including amphetamines) and sedatives (including phenobarbital) seem to cause developmental defects within the nervous system. Cocaine has been found to cause placental abruptions, causing death of pregnant woman and baby, or premature delivery. Opioids like heroin often cause intrauterine growth retardation and cause infants to be born addicted. Also, newborns addicted to heroin or other opioids are likely to have learning disabilities later in life.

Hallucinogens (like LSD or belladonna) differ from the other categories of drugs in that they can cause birth defects even if they are taken years before pregnancy. Hallucinogens have been found to cause chromosomal damage at the time of use. Because chromosomes in egg cells (ova) and in spermatogenic cells may be damaged, a wide variety of birth defects can occur. Similarly, if hallucinogens are used during early pregnancy, chromosomal damage may occur, leading to various types of birth defects. Many pregnant drug-users use more than one type of drug. This complicates the situation in that drugs may interact to have a significantly different and greater effect on the fetus.

Drug Treatment for Pregnant Women

Pregnant women who use heroin or other opioids are often treated with methadone . While this is an effective immediate treatment, it does not prevent a fetus from being born addicted. Suboxone (also known as buprenorphine) is drug used since the 1980s to treat opioid addiction (first used in the United States for this purpose in 2002). According to the National Institute on Drug Abuse, the findings of a 2012 clinical trial suggest that buprenorphine may be a safe and effective alternative to methadone, the standard treatment for opioid dependence during pregnancy. Infants born to mothers on heroin, methadone, or suboxone are evaluated using the neonatal abstinence (Finnegan) scale. The use of this scale determines the course of treatment in stopping the use of these substances.

Bibliography

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Huizink, Anja C., and Eva J. Mulder. “Maternal Smoking, Drinking, or Cannabis Use During Pregnancy and Neurobehavioral and Cognitive Functioning in Human Offspring.” Neuroscience Biobehavioral Review 30 (2006): 24–41. Print.

Rayburn, William, F. “Maternal and Fetal Effects from Substance Use.” Clinical Perinatology 34 (2007): 559–71. Print.

Whitten, Lori. “A Multisite Clinical Trial Lays Groundwork for Improving Care for Mothers and Babies Affected by Opioid Dependence.” Natl. Inst. on Drug Abuse. NIH NIDA, July 2012. Web. 28 Oct. 2015.