Older studies conducted with laboratory animals seem to indicate that there may be a relationship between the active cannabinoids found within Cannabis and the proper function of the reproductive system. The main psychoactive cannabinoid found in Cannabis, delta 9 tetrahydrocannabinol (THC) may inhibit the secretion of certain pituitary hormones including luteinizing hormone (LH), follicle-stimulating hormone (FSH), and prolactin. 
These hormone changes brought on by the introduction of THC led to decreased steroid hormones alongside a disruption in both ovulation and spermatogenesis.  The hypothalamus is a main brain area for THC interaction with CB1 and CB2 receptors and adverse reproductive health conditions brought on through chronic use due to the effects of THC on pituitary hormone production may be reversed with hypothalamic releasing factors. 
Another study conducted on mice given a 50mg/kg dose of THC for 7 days starting on the 20th day of gestation showed that THC can reduce postnatal viability, alter male reproductive behavior at maturity, and drastically reduce seminal vesicle weights.  THC can cross the placental barrier and may possibly lead to some of these negative effects caused by hormone disruption.
The same study was conducted using cannabichromene (CBC) as both a stand-alone interaction and with CBC + THC. The results showed that CBC alone did not display the same effects on reproductive health and that when used in a combination with THC, it antagonized the effects of this cannabinoid in the animals of the study.
- Smith, CG, Asch RH. Acute, short-term, and chronic effects of marijuana on the female primate reproductive function. NIDA Res Monogr. 1984
- Hatoum, N.S., et al. Perinatal exposure to Cannabichromene and delta 9 tetrahydrocannabinol: Separate and combined effects on viability of pups and on male reproductive system at maturity. Toxicology Letters. May 1981.