Many drugs of abuse (see DRUG ABUSE) taken during PREGNANCY can have effects on the FOETUS during DEVELOPMENT. The placental barrier exists between the circulatory systems of mother and foetus. It protects the foetus from the maternal IMMUNE SYSTEM but many types of MOLECULE do cross from mother to foetus—most are necessary NUTRIENTS, but other agents can cross over (which is why physicians take such care in prescribing therapeutic drugs to pregnant women). Infants rarely if ever come into the world already addicted, but drugs of abuse can have a variety of effects, including induction of the NEONATE NEUROLOGICAL SYNDROME. This Syndrome is present within a day of birth and is associated with a variety of signs (including abnormal SLEEP patterning, TREMOR and SEIZURES, FEEDING difficulty and general irritability) and increased risk of other disorders, including SUDDEN INFANT DEATH SYNDROME.
It is also important to recognize that, because NEURODEVELOPMENT is not uniform across time, the period in pregnancy during which drugs are taken is often critical.
ALCOHOL, TOBACCO, MARIJUANA, COCAINE and CRACK COCAINE, HEROIN, PCPA and LSD have been associated with various problems including altered MORPHOLOGY (such as low birth weight, often attendant on premature birth, or small head circumference) and behavioural disturbances, initially in sleep and feeding, though other problems may be present, and LEARNING impairments may become apparent later. Probably the most dramatic effects are of alcohol, which causes FOETAL ALCOHOL SYNDROME. Crack cocaine is thought to induce particular problems in so-called CRACK BABIES. One possible mechanism for this is the induction of foetal HYPOXIA, which is associated with a variety of problems in the foetus and PLACENTA during pregnancy. When first identified it was thought that crack babies had a variety of intellectual and behavioural impairments but later research has questioned the severity of the problem. Because heavy drug abuse is often associated with poverty and poor domestic quality, it is difficult to dissociate the effects of the drug in utero from the more pervasive effects of deprivation. This is not to say that one should minimize the problems associated with maternal drug abuse, but to indicate that the problems need to be set in a wider context.
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