Embryo Incubator: Humidity and Pregnancy Rate

In this study, the Lee Women's Hospital research team analyzed and explored the embryo cultivation environment during the IVF treatment based on academic paper. They compared two different humidity conditions: the humid culture incubator and the dry culture incubator. The study investigated the differences in clinical pregnancy rates between these two humidity conditions.
 

Does the humid culture system contribute to an increase in the clinical pregnancy rate among infertile patients?

Embryos develop in an environment with a certain level of humidity within the uterus. Some experts suggest that "dry culture (DC)" conditions might have a negative impact on embryo development. Overseas studies have indicated that dry conditions can accelerate the evaporation of the culture medium, leading to a gradual increase in osmotic pressure. This has been proven detrimental to embryos in various animal studies. High osmotic pressure (exceeding 300 mOsm/kg) is also associated with developmental stagnation, changes in gene expression, and epigenetic modifications.

In some experimental studies, it was found that embryos cultured under humid conditions have a higher pregnancy rate. However, Dr. Huang Junjia, the Director of the IVF Laboratory at Lee Women's Hospital, mentioned that there is a challenge in the clinical setting regarding the humid culture system. He explained, "The humid environment in the humid culture embryo incubator is maintained by moisture within the pipelines, which unfortunately can lead to mold contamination of the embryo culture dishes. To address this issue, Lee Women's Hospital has adopted several approaches through clinical trials that prevent mold contamination while maintaining the embryo incubator humidity."

Firstly, Lee Women's Hospital employs a dry culture system with a Time-Lapse embryo monitoring culture incubator that doesn't use circulating pipelines. The selected model allows for the thickest oil to be placed on top of the embryo culture medium, as shown in the image below, with 180μl of medium and 4.5mm of oil. This approach maximizes the prevention of water evaporation.



Originally, the Time-Lapse embryo monitoring culture system required changing the culture medium after 5 days of incubation under oil. However, Lee Women's Hospital's research found that even with this approach, the evaporation of water still led to an increase in the osmotic pressure of the medium. Therefore, they adjusted their protocol to change the medium every 3 days while maintaining a thick layer of oil. This change helps to keep the embryos moist and maintain the appropriate osmotic pressure.

Additionally, Lee Women's Hospital has a specialized incubator with a unique gas supply system. This system doesn't rely on closed-loop pipelines but has separate air intake and exhaust vents. Fresh air enters through the intake vent, ensuring a controlled environment. In this setup, the humidity is adjusted before introducing it into the incubator through the air intake vent. This approach prevents mold contamination by avoiding closed-loop circulation and ensures that the embryos remain moist.

In addition to deriving insights from substantial clinical research, we also draw from international papers to absorb the essence of others' studies. These are crucial factors in achieving successful embryo cultivation. Even the millions of dollars' worth of advanced equipment require meticulous research by embryologists. Lee Women's Hospital leverages over 40 years of accumulated data for thorough analysis and interpretation. Dr. Huang Junjia, the convener of the Embryologists at the Taiwan Society of Reproductive Medicine, continues the tradition of experience sharing, striving to contribute to all professionals in the field of reproductive medicine.