Drugs in pregnancy

U.S. Code of Federal Regulations requires that certain drugs and biological products must be labelled very specifically with respect to their effects on pregnant populations, including a definition of a "pregnancy category". These rules are enforced by the Food and Drug Administration (FDA).[3][4] The FDA does not regulate labelling for all hazardous and non-hazardous substances and some potentially hazardous substances are not assigned a pregnancy category.

Australia’s categorisations system takes into account the birth defects, the effects around the birth or when the mother gives birth, and problems that will arise later in the child's life caused from the drug taken. The system places them into a category of their severity that the drug could cause to the infant when it crosses the placenta(Australian Government, 2014).[5]

Valproic acid, and its derivatives such as sodium valproate and divalproex sodium, causes cognitive deficit in the child, with an increased dose causing decreased intelligence quotient.[6] On the other hand, evidence is conflicting for carbamazepine regarding any increased risk of congenital physical anomalies or neurodevelopmental disorders by intrauterine exposure.[6] Similarly, children exposed lamotrigine or phenytoin in the womb do not seem to differ in their skills compared to those who were exposed to carbamazepine.[6]

Alcohol passes easily from the mother's bloodstream through the placenta and into the bloodstream of the fetus. Since the fetus is smaller and does not have a fully developed liver, the concentration of alcohol in its bloodstream lasts longer increasing the chances of detrimental side effects.[7] The severity of effects alcohol may have on a developing fetus depends upon the amount and frequency of alcohol consumed as well as the stage of pregnancy. Rates of alcohol consumption can generally be categorized in one of three ways: heavy drinking (more than 48-60g ethanol/day), moderately high drinking (24-48g ethanol/day), and binge drinking (4-5 drinks/90g ethanol at a time).[8] Heavy drinking and binge drinking are closely associated with a higher risk of fetal alcohol spectrum disorders (FASDs). The most severe form of FASD is fetal alcohol syndrome (FAS). This used to be the only diagnosis for fetal disorders due to alcohol consumption but the term was broadened to a "spectrum" due to the variety of abnormalities observed in newborns. This was most likely because of the different amounts of alcohol ingested during pregnancy indicating that there is not a clear, specific dose that determines if a fetus will be affected by alcohol or not. This is why it is very important for pregnant women to abstain from alcohol use altogether. FAS is characterized by slower physical growth, distinct facial abnormalities including smooth philtrum, thin vermilion, and short palpebral fissures, neurological deficits, and/or smaller head circumference. Other problems associated with FASD include delayed or uncoordinated motor skills, hearing or vision problems, learning disabilities, behavior problems, and inappropriate social skills compared to same-age peers. Those affected are more likely to have trouble in school, legal problems, participate in high-risk behaviors, and develop substance use disorders themselves.

Cannabis consumption in pregnancy might be associated with restrictions in growth of the fetus, miscarriage, and cognitive deficits.[9] Cannabis is the most frequently used illicit drug amongst pregnant women.[10] Tetrahydrocannabinol, an active ingredient in cannabis, can both cross the placenta and accumulates in high concentrations in breast milk.

Tobacco is the most commonly used substance amongst pregnant women, at 25%. Similar to cocaine, nicotine is able to cross the placenta and accumulates within fetal tissues. Based on a literature review conducted between 2007 and 2008,[11] children born to women who smoked heavily were more susceptible to behavioral problems such as ADHD, poor impulse control, and aggressive behaviors. A number of studies have shown that tobacco use is a significant factor in miscarriages among pregnant smokers.[12] Tobacco contains carbon monoxide, which has the potential to prevent the fetus from receiving sufficient oxygen. Other health concerns tobacco poses are premature birth, low birth weight, and an increase risk of sudden infant death syndrome (SIDS) of up to three times compared to infants not exposed to tobacco. Smoking and pregnancy, combined, cause twice the risk of premature rupture of membranes, placental abruption and placenta previa. In addition to the fetus, women in general who smoke heavily are less likely to become pregnant.

No specific disorders or conditions have been found to result for people whose mothers used cocaine while pregnant.[13] Studies focusing on children of six years and younger have not shown any direct, long-term effects of PCE on language, growth, or development as measured by test scores.[14] PCE also appears to have little effect on infant growth.[15] However, PCE is associated with premature birth, birth defects, attention deficit hyperactivity disorder, and other conditions. The effects of cocaine on a fetus are thought to be similar to those of tobacco and less severe than those of alcohol.

Opioids include heroin, fentanyl, painkillers such as oxycodone and methadone. Women who abuse opioids during pregnancy are at a higher risk for premature birth and for lower birth weight. There is no consensus on the effects on cognitive abilities.[16]

Opioid abuse is the main cause of neonatal abstinence syndrome, which is where the baby experiences withdrawals from the drug they were exposed to during the pregnancy. Typical symptoms may include tremors, convulsions, twitching, excessive crying, poor feeding or sucking, slow weight gain, breathing problems, fever, diarrhea, and vomiting amongst others.[17]

Prenatal methamphetamine exposure has shown to negatively impact brain development and behavioral functioning. A 2019 study further investigated neurocognitive and neurodevelopmental effects of prenatal methamphetamine exposure. This study had two groups, one containing children who were prenatally exposed to methamphetamine but no other illicit drugs and one containing children who met diagnosis criteria for ADHD but were not prenatally exposed to any illicit substance. Both groups of children completed intelligence measures to compute an IQ. Study results showed that the prenatally exposed children performed lower on the intelligence measures than their non-exposed peers with ADHD. The study results also suggest that prenatal exposure to methamphetamine may negatively impact processing speed as children develop. [18]