The HSG is an X-ray of the uterus and tubes tells whether the tubes are open or blocked. It gives little information about the outside of the tubes & the pelvis and whether there is any endometriosis or evidence of previous infection. A laparoscopy does all these things but requires general anaesthesia and is a surgical procedure, both of which carry small but definite risks.
Therefore we usually arrange an HSG first and only if there are any abnormalities seen do we recommend a laparoscopy. A normal HSG result usually also means that the laparoscopy will be normal.