Rosen 1987a.

Methods	Randomised trial with concurrent eligible patients outside of the RCT. The non‐RCT patients were not in the RCT because they declined randomisation. The non‐RCT patients were followed‐ up identically to the RCT patients. Patients undergoing oocyte retrieval via laparoscopy. No losses to follow up.
Data	Non‐RCT patients were compared to RCT patients who received the same treatment. Ages unknown.
Comparisons	Two RCT arms, each in common use, and each of them were compared with similarly treated eligible non‐RCT patients. Control‐N: Aneasthetic with NOx. Control‐O: Anaesthetic without NOx.
Outcomes	Clinical outcomes were assessed in all the patients. Length of followed up unknown. Main outcome was number not pregnant.
Notes	The two RCT treatments were not statistically different.