The fertility treatment in vitro fertilisation (IVF), sometimes including intra-cytoplasmic
sperm injection (ICSI), involves the creation of embryos in a laboratory. These embryos are
then transferred into the womb of the patient with the hope of a resulting pregnancy and live
birth. Embryos can also be cryopreserved (frozen) and stored, and then later replaced in a
cycle called frozen embryo transfer (FET). There are several methods of preparing the
patient's womb to receive the frozen-thawed embryo(s) but commonly embryos are replaced
during a medicated cycle. Usually oestrogen and progesterone are administered to prepare the
womb lining for embryo transfer at the appropriate time, and in addition a drug called a GnRH
antagonist is administered to prevent a women's own hormones from interfering with this
process as it is thought this might lead to higher numbers of cycles being cancelled.
However, there is some suspicion that this drug (GnRH antagonist) may not be required and
that women are using this drug unnecessarily.
Some clinics do not use GnRH antagonists in FET cycles, but the investigators do not know if
they have higher rates of cancelled cycles as a result.
This pilot study aims to compare cycles of medicated FET using oestrogen and progesterone,
either with or without pituitary suppression in the form of GnRH antagonist (Cetrotide), in
patients over the next 18 months who are planning FET cycles at Oxford Fertility, UK to find
out if both give the same chance of having a baby, which treatment is better for patients and
to assess the feasibility of undertaking a future larger study. Cetrotide is a marketed and
well-known medication and any risk or serious adverse effects are unlikely. The study is an
open label prospective randomised controlled trial. Funding for the medication (Cetrotide) is
provided by Oxford Fertility.