A new study published in Frontiers in Endocrinology has found that short-term insemination during in vitro fertilization (IVF) cycles does not reduce the chances of live birth compared to the traditional overnight method. The research focused on patients who had only one or two oocytes retrieved, a group that often faces higher rates of cycle cancellation and increased emotional and financial stress.
The study was conducted at a single reproductive medicine center and analyzed 2,392 IVF cycles between January 2013 and December 2022. Of these, 2,057 cycles used short-term insemination—where sperm and oocytes are co-incubated for five hours—and 335 used overnight insemination, which lasts about 17 hours. After matching patients based on baseline characteristics such as age, ovarian reserve, stimulation parameters, and sperm quality, the researchers found no significant difference in cumulative live birth rates between the two groups.
According to the authors: "Cumulative live birth rates were similar between short-term and overnight insemination, both before and after matching. These findings indicate that reducing sperm–oocyte exposure time did not compromise cumulative live birth outcomes."
Short-term insemination showed advantages in some laboratory outcomes. It resulted in higher normal fertilization rates and fewer instances of abnormal fertilization compared to overnight methods. There were also lower embryo transfer cancellation rates and fewer cycles with no embryos available when using short-term insemination.
"Short-term insemination improved certain fertilization and embryo parameters," the researchers noted. "These improvements did not translate into a statistically significant increase in overall live birth rates." They added: "Multivariable analyses confirmed the absence of an adverse effect of short-term insemination on cumulative live birth."
The study also observed that for patients whose embryos were cultured to the blastocyst stage, there was a trend toward higher cumulative live birth rates with short-term insemination. However, this difference was not statistically significant after adjusting for other factors.
While intermediate clinical outcomes favored short-term insemination—including reduced freeze-all cycle rates—the primary endpoint of cumulative live births remained unchanged between groups. The authors emphasized that these intermediate benefits may still be important for patient experience: "Cycle cancellation is frequently reported by patients as one of the most emotionally challenging aspects of IVF," though they acknowledged emotional outcomes were not directly measured.
The researchers concluded: "In IVF cycles retrieving only one or two oocytes, short-term insemination achieved cumulative live birth rates comparable to overnight insemination without compromising overall success. Importantly, it reduced embryo transfer cancellations and improved several laboratory indicators of embryo quality."
They cautioned that interpretation should consider limitations such as the retrospective design, single-center setting, changes over time in practice patterns, and laboratory-specific variables.
