Choosing One or Two Embryos: What the Numbers Say

The study looks at how many embryos—one or two—are transferred during fresh IVF cycles when the embryos are at the cleavage stage. Researchers used a statistical method called propensity score matching to compare success rates and risks between the two groups. First, they gathered data from a large group of patients who had fresh embryo transfers. They matched individuals in the single‑embryo group with those in the double‑embryo group so that age, health status, and other factors were similar. This helps make the comparison fair. The main outcome measured was live birth rate per transfer. The results showed that transferring one embryo had a slightly lower chance of resulting in a live birth compared to two embryos. However, the difference was not huge.Safety concerns were also examined. The study found that transferring two embryos increased the risk of multiple pregnancies, which can lead to complications for both mother and babies. The chance of a singleton birth was higher when only one embryo was transferred. When looking at other complications, such as miscarriage or ectopic pregnancy, the numbers were similar between the two groups. This suggests that the main trade‑off is between higher success with two embryos and higher risk of multiples. The authors concluded that the decision should balance a patient’s desire for pregnancy against the potential health risks. For some, starting with one embryo and adding another if needed might be a prudent strategy. Overall, the research provides evidence that while two embryos can boost success rates, they also raise the likelihood of twins or triplets. Patients and doctors should discuss these trade‑offs before deciding.