Follicular fluid pH changes following intraperitoneal exposure of Graafian follicles to carbon dioxide: a comparative study with follicles exposed to ultrasound.

Follicular aspiration to obtain oocytes is generally performed via laparoscopy after creating a pneumoperitoneum with carbon dioxide. Such a procedure has been shown to reduce the rate of in-vitro fertilization of human oocytes and affect the rate of cleavage of rabbit embryos. These adverse effects may be caused by a reduction in follicular fluid pH due to diffusion of carbon dioxide into the follicle. In laparoscopic oocyte retrievals, a negative correlation was observed between duration of CO2 exposure and follicular fluid pH, whereas in ultrasound-guided retrievals, the pH remained unchanged. The mean pH in 78 follicles aspirated at laparoscopy was 7.22 +/- 0.03 compared with 7.62 +/- 0.01 in 35 follicles aspirated under ultrasound guidance (P = 0.0003). The results also indicate that oocytes in preovulatory follicles are surrounded by fluid that is more alkaline than plasma. Hence, the acidic environment treated by CO2 may be deleterious to subsequent reproductive function of the oocyte.