Purpose: To investigate whether commonly used test tube warming devices maintain a constant temperature in follicular fluid aspirates.
Methods: By using a digital thermocouple, temperature was measured and comparisons were made between an analog dry block heater, a digital dry block heater, and a thermostatic test tube heater.
Results: For small fluid volumes, temperature in the block heaters increased above 37 degrees C after being in the block for over 2 min. The thermostatic heater maintained a constant temperature, but this was below the factory setting of 36.9 degrees C. Temperature maintenance was influenced by fluid volume in each tube.
Conclusions: One of the key factors in the handling of gametes and embryos is the maintenance of constant temperature. Test tube warming devices require verification of their ability to maintain fluid at the desired temperature. Temperature may vary with fluid volume and the type of test tube warming device used.