Assisted hatching
The zona pellucida or coating of an embryo is opened mechanically, chemically or with a laser, with the aim of assisting the embryo to emerge and improve implantation and pregnancy rates.
Assisted Reproductive Technology (ART)
'Assisted conception' is the general term that covers the range of medical treatments that are used with the aim of achieving a live birth. The focus of ART is on the use of the more involved medical procedures such as IVF, GIFT and ICSI.
Biochemical pregnancy
Early embryo development begins but does not become established, so pregnancy tests are positive at first but become negative. This is usually followed by a late period.
Blastocyst
A stage of embryo development that occurs about five days after fertilisation when the embryo contains quite a few cells. A fluid filled sac forms in the mass of cells, fed by the outer layer of trophoblast of cells. The cells contained within the trophoblast layer will develop into the embryo, while the trophoblast cells form the placenta and membranes. Before this stage the embryo is occasionally referred to as the pre-embryo.
Blighted ovum
This is a common form of miscarriage based on ultrasound diagnosis showing that there is a pregnancy sac but no embryo.
Down-regulation
Hormone medication (a gonadotrophin releasing hormone-agonist such as Synarel or Lucrin), is commenced in the luteal phase of the menstrual cycle prior to the planned IVF cycle. The aim is to lower levels of the woman's hormones, particularly luteinising hormone and progesterone, to avoid their interference with planned synthetic hormone stimulation. May be referred to as a 'long protocol'. The gonadotropin stimulating hormones are commenced once the ultrasound shows suppression of ovarian activity, i.e. other endormetium and no folicles greater than 8mm diam on the ovaries.
Ectopic pregnancy
A pregnancy growing outside the uterus, almost always in the fallopian tube. It cannot continue to grow beyond a couple of months gestation and must be removed for the woman's safety.
Embryo
'Embryo' comes from the Greek word meaning 'to swell and grow'. When we use the word we mean a fertilised egg which has divided at least once to reach the two-cell stage or beyond. The embryo is referred to as a foetus from about the 9th week.
Embryo biopsy
The process of removing a cell from an embryo for genetic analysis (see Pre-implantation Genetic Diagnosis).
Embryo Transfer (ET)
The transfer of the embryo from a sterile plastic dish, through a fine plastic tube into the woman's uterus. The transfer usually occurs 2 days after ovum pick-up in an IVF cycle and two days after ovulation in a natural thaw cycle.
Embryo cryopreservation (Frozen embryo)
The freezing of embryos for storage until they can be thawed and transferred to the uterus in a later cycle.
Endometrium
The lining of the uterus which builds up due to increasing amounts of oestrogen during the follicular phase of the menstrual cycle. After ovulation, under the influence of progesterone, the lining of the uterus goes through a secretory phase and is prepared for an embryo to embed. If pregnancy does not occur the endometrium is shed - known as menstruation or a period.
Fertilisation
The process in which a sperm enters an egg and triggers further development. We say fertilisation has occurred when we see the nucleus of the sperm together with the egg nucleus inside the egg cell under the microscope.
Flare protocol.
Synthetic hormone medication is commenced in the first couple of days of the woman's period during a stimulated IVF cycle. The gonadotrophin releasing hormone agonist(eg Synarel or Lucrin) is started a day before the gonadotrophin injections (eg Ganal F or Puregon). Known also as a 'short protocol'.
Follicle
The fluid-filled swelling in the ovary which contains the egg. The egg itself is too small to be seen and measured using ultrasound. We expect a follicle to grow to about 20 mm diameter by the time of ovulation. During stimulation with hormonal medications there may be many follicles seen on ultrasound.
Gonadotropin
Hormones produced by the pituitary, which control the action of the ovaries and testes. Follicle stimulating hormone (FSH), luteinising hormone (LH) and human chorionic gonadotropin (HCG) are gonadotropins.
Gonadotropin releasing hormone (GnRH-agonists)
Hormones that stop the release of the gonadotropins, thus interrupting ovarian and testicular function.
Insemination
The addition of sperm to the eggs in the laboratory during the IVF process. Can also refer to the process of injecting sperm into the woman's vagina, cervix or uterus.
In Vitro Fertilisation
This literally means fertilisation in glass. In fact in modern IVF laboratories, sperm and eggs are put together in disposable sterile plastic dishes or tubes.
In Vivo Fertilisation
Term used when fertilisation occurs within the woman's body.
Oocyte
Egg produced by the woman each month in a follicle in her ovary, also known as an ovum.
Ovarian Stimulation
The drug treatment that is used to develop several follicles in the ovaries during an IVF cycle, instead of the usual single follicle. This enables several eggs to be harvested at ovum pick-up, which increases the couples' chances of pregnancy. Stimulation of the ovary with the appropriate drug(s), eg clomiphene citrate, gonadotropin is also used in women with disorders of ovulation.
Ovum pick-up (OPU)
Visually guided by transvaginal ultrasound, a needle is passed through the vaginal wall and into the follicle. The egg is obtained from the follicle using gentle vacuum pressure. Known also as 'egg pick-up', 'follicle aspiration' or 'egg collection'.
Polyspermia
More than one sperm has entered the egg leading to an abnormal number of chromosomes. The resulting embryo is therefore not transferred.
Preimplantation Genetic Diagnosis (PGD)
One (or occasionally two) cell is carefully removed from the embryo on about day three, when it has reached the six to eight-cell stage. The biopsied cells are used for genetic diagnosis, at present by FISH (fluorescent In-situ hybridisation) or CGH (comparative genomic hybridisation). |
