Marijuana (THC) reported use is in a range from 5 to 30 percent among pregnant women. The use of smoking and the concomitant use of marijuana make the independent effects difficult to decipher. Some studies have shown that:

1. Regular use shortens length of gestation
2. Use increases the risk of small for dates babies (intrauterine growth retardation)
3. Birth length has also been noted to be effected (shorter).
4. Marijuana is not a teratogen (does not cause birth defects) but can cause neuro-behavioral symptoms such as altered visual responses, tremors, jitteriness; such babies are difficult to comfort and settle.
5. No lasting effects on motor development have been reported
6. In animals, ovulation can be affected and sperm counts decrease with use