The dried leaves and flowering parts of the hemp plant are known in different parts of the world by a variety of names, including marijuana, pot, ganja, and bhang. The resinous extract of the plant is termed hashish.

A large number of active compounds with various effects are found in cannabis plants, but the primary active agent of marijuana is delta-9-tetrahydrocannabinol (THC). This agent is also available as dronabinol (Marinol) for increasing appetite and controlling nausea. Although the plant materials may be eaten, or in some cases, extracted and administered parenterally, most clinical information is focused on the reproductive toxicity of the plant material when smoked.

Occasional use of marijuana was not significantly related to the risk of low birth weight, smallness for gestational age, or preterm delivery (Am J Epidemiol 124:986-93, 1986). Lester and Dreher (Child Dev 60:765-770, 1989) studied ganja (three- to four-times the amount of THC per marijuana cigarette) users in Jamaica. Infants of the ganja-using mothers weighed more than those of control mothers, and did not have abnormal scores when evaluated with the Brazelton Neonatal Assessment Scale.

A retrospective analysis utilizing historical data was performed with review of 417 patients who gave a history of marijuana use: There was no association between marijuana use and prematurity or congenital malformations (Am J Perinat 7:36-38, 1990). Marijuana use was strongly associated with the use of alcohol and tobacco.