Common Substances Abused During Pregnancy: Both are obtained from the hemp plant, cannabis. It is associated with short-term memory and respiratory infection. When smoked, they produce tachycardia and a sense of well-being. Some women use marijuana to counteract nausea in early pregnancy. Frequently part of polydrug abuse, so their effects on fetal development are not well documented. A frequent user may not be able to breastfeed because of reduced milk production and the risk to the newborn from excretion of the drug in the milk.