Different options exist within IVF treatment, and we’re learning more about their effectiveness ZEPHYR/SCIENCE PHOTO LIBRARY Natural ovulation is just as effective as hormone treatment for preparing the uterus for a frozen embryo transfer following in vitro fertilisation (IVF) and carries fewer risks, according to a large, randomised trial. Emerging evidence suggests that for women who respond well to IVF (by being able to produce lots of eggs), freezing embryos and transferring them in a later cycle may improve success rates. As a result, frozen embryo transfers now account for the majority of embryo transfers globally. Following IVF, a frozen embryo must be transferred to the uterus at a precise point in the menstrual cycle, when the endometrium – the blood vessel-rich inner lining of the uterus – is thick enough to support implantation. Women can either choose to use a medicated cycle, where oestrogen and progesterone are taken throughout the month to prepare the uterus, or their natural cycle, if it is regular, which relies on monitoring hormones produced by the body. Which choice …