Marijuana/Tobacco

marijuana

          Marijuana is derived from the Indian cannabis sativa plant initially found in Central Asia but may be grown anywhere.  It may commonly be referred to as "MaryJane" or THC (for Δ-9-tetrahydrocannabinol.)  Currently, debate exists about legalizing marijuana for medical purposes, specifically in the treatment of glaucoma and to control the nausea and anorexia associated with cancer chemotherapy.  Marijuana is prepared by drying the plant’s leaves and flowers and smoked in cigarettes, cigars, or pipes but can be added to cookies or brownies and taken orally.  Marijuana is lipophilic, is stored in the brain and other fat-rich areas of the body and slowly released from these stores.  This may account for the late cognitive or behavioral effects seen in individuals and/or the absence of signs of withdrawal when use is abruptly discontinued.  Marijuana is a mind-altering, addictive drug that can result in dependence and may be  associated with simultaneous experimentation with and use of other legal and illegal substances.  

            Following ingestion, by whatever form, the individual experiences euphoria, relaxation, diminished inhibitions, and an increased perception of textures, smells, tastes, sounds, and sights.   They will experience impaired problem-solving skills, difficulty organizing thoughts and carrying on a conversation.   Peak plasma concentration following smoking marijuana occurs within 7-10 minutes and can last from 20-30 minutes.  Peak plasma concentration with oral consumption occurs within 30-60 minutes and can last upwards of 2-3 hours.  The drug is metabolized predominately by the liver but some is metabolized by the lungs when inhaled and by the intestines when consumed orally.  The use of marijuana by adolescents, many before the age of 18, is a major health problem with social, academic, developmental and legal consequences, especially the pregnant adolescent.  Marijuana crosses the placenta and will show up in the infant’s urine in the 1st day of life and in the stool for up to 3 days; it's presence has also been documented in human milk.

           There is documentation supporting marijuana-related effects in the mother manifesting in the cardiovascular, pulmonary, reproductive and immunologic systems.  

Cardiovascular:  Tachycardia, Slight rise in BP

Respiratory:  Initially bronchodilation, but prolonged use will lead to bronchoconstriction and airway obstruction, neoplastic lung changes similar to cigarette smokers

Reproductive: Males:  Diminished sperm count & sperm motility, Decreased testosterone levels;  Females:  Irregular ovulation, Decreased pituitary gonadotropin levels, Presence in breastmilk

Immunologic:  Affects antitumor activities, Possible immunosuppression.

Unfortunately, few studies exist documenting the fetal/infant and/or long-term effects of prenatal exposure to marijuana.  Marijuana may be teratogenic in the animal population but available human studies linking its use to congenital anomalies have been inconclusive.  It is difficult to separate out marijuana’s effects among a population that has traditionally abused multiple substances simultaneously.  There have been a small number of studies reporting a fetal alcohol-like syndrome but, again, these studies have been inconclusive.  Little documentation is available to support marijuana as an independent risk factor for pre-term labor though some researchers report “a tendency” for shorter gestations.  Likewise, prenatal marijuana use may result in smaller babies (birthweight) and a smaller head circumference in the infant.  No studies documenting effects/changes in abortion rates, anomalies or fetal/infant growth patterns over time were located.  Medical problems that continue to be investigated and may possibly be linked to prenatal marijuana use are an increased risk for childhood leukemia (10 times the risk) and ophthalmic problems such as myopia, strabismus, and abnormal  oculomotor functioning.  Since prenatal marijuana exposure may potentially produce adverse effects the medical community continues to question the safety of and discourages the use of marijuana during pregnancy.

SMOKING

            The injurious effects of tobacco on the fetus/infant have been well documented for many years.  In 1980 the United States Surgeon General reported 20-30% of low-birth-weight births could be traced to maternal tobacco use during pregnancy.  Although smoking in the United States has decreased, recent data suggests that approximately 20% of pregnant women smoke prior to and continue to smoke throughout their pregnancy.  The largest group of pregnant smokers continue to be Caucasian or non-Hispanic white women as compared to 10% of African-American and 4% of Hispanic women.  Caucasian women also smoke at a higher consumption (more packs/day) level than the women of the other ethnic groups.  Maternal effects of cigarette smoking during a pregnancy include:

Less likely to be married

Have less education

Have lower incomes

Keep fewer prenatal care visits

Spontaneous abortion

Preterm labor

Premature rupture of the membranes

Placental abruption

Placental previa.

        Fetal/Infant adverse outcomes are related to the effects of two key ingredients in cigarette smoke:  carbon monoxide (CO) and nicotine; both readily cross the placenta and enter fetal circulation.  The CO binds with hemoglobin to form carboxyhemoglobin, reducing the oxygen-carrying capacity of blood leading to fetal hypoxia; meanwhile, nicotine significantly reduces the uterine blood flow and affects the fetal cardiovascular and central nervous systems.  Whether nicotine also interferes with fetal oxygenation and acid-base balance continues to be investigated.  Other components of cigarette smoke--cadmium and toluene--have also be shown to cause fetal growth retardation.  Fetal/Infant sequelae to cigarette smoke include:

Intrauterine growth restriction (IUGR)/Small for Gestational Age (SGA):  growth restriction occurs at all gestational ages with a reduction in birthweight ranging from 100-350 grams

Prematurity

Smaller head circumference & height that may persist for 7-14 years of age

Decreased auditory, language, and neurobehavioral outcome

Lowered IQ & cognitive performance

Exposure to significantly high levels of nicotine in breastmilk, if the mother continues to smoke post-delivery

Increased incidence of asthma, bronchitis, pneumonia

Increased risk of SIDS

Males:  More adversely affected compared to female counterpart.

These risks are a direct relationship and dose-dependent.  In other words; the greater the use and the longer the use, the greater the mother's chance of having one of the outcomes noted above.  As to dose-dependency:  if the woman smokes < 1 pack of cigarettes/day her risk of having a premature birth increases by ~ 53%.  On the other hand, if she consumes > 1 pack of cigarettes/day, her risk increases by 130%.  Evidence does exist that reducing the number of cigarettes/day has a positive impact on infant outcomes.  In fact, if smoking can be discontinued by the end of the 1st  trimester, the intrauterine fetal growth pattern should be similar to that of the non-smoker.  In spite of this, women are less likely to reduce or discontinue cigarette smoking than they are alcohol and/or other drug use during pregnancy.  About 2/3  of women who smoke before pregnancy will continue throughout the pregnancy and continue postnatally, thus exposing the newborn to 2nd hand smoke and increasing his/her risk for respiratory diseases and SIDS.  

            While the negative effects of cigarette smoking on fetal growth and development have been stressed for many years, the adverse neurobehavioral effects now recognized have not.  Yet, these adverse neurobehavioral may be even more important.  Again, if mom continues to smoke and breastfeed, the infant is exposed to significantly high nicotine levels in the breastmilk which may have, yet to be determined,  ongoing, long-term effects.  Every effort should be made to encourage the pregnant woman who smokes to discontinue smoking during her pregnancy, or at the very least, significantly limit her consumption.

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