Patient Information

Here you can find definitions and explanations for the terms used throughout our website. If you have any questions don’t hesitate to contact us.

Assisted hatching

A micromanipulation process used to breach the zona pellucida and hence facilitate hatching of the blastocyst. Common approaches include the used of mechanical partial zona dissection (“PZD”), acid Tyrodes or a laser.


The complete absence of spermatozoa in a man’s semen caused either by an obstruction or by failure to produce spermatozoa in the testes.


The stage of development at which the embryo is able to undergo implantation. Human embryos should reach this stage on Day 5 after fertilization. A blastocyst comprises an outer layer of cells, the trophoblast, that enclose the inner cell mass and a cavity, the blastocoel.


A word used loosely to describe those stages of the development of an animal from the fertilized oocyte (i.e. zygote) until the fetus, i.e. about the first 8 weeks of human development; the stages before implantation are sometimes referred to as the pre-embryo.

Embryo biopsy

The procedure whereby one or two cells are removed from an embryo (usually performed at the 8-cell stage on Day 3 after fertilization) for genetic analysis


The fusion of the male and female gametes, a spermatozoon with an oocyte, to create a new individual. A fertilized oocyte is termed the zygote


Human chorionic gonadotrophin (more correctly β-hCG), a hormone that is produced by the early embryo and the ovary to regulate the early stages of pregnancy. Testing for increased levels of β-hCG is the basis of a pregnancy test. As a pharmaceutical, hCG is also given to “trigger” ovulation in women undergoing ovarian stimulation for IVF


The process whereby the blastocyst stage embryo burrows into the lining of the uterus, or endometrium, to establish a pregnancy.

In-vitro fertilization (IVF)

Literally, fertilization “in glass”. This technique, whereby oocytes and spermatozoa are mixed in the laboratory to achieve fertilization, is used as a treatment for infertility when the process cannot occur naturally inside the woman’s body.


A medical term often used to described low or poor sperm motility combined with a low sperm concentration. However, since it does not describe any particular presentation, it is not considered a useful scientific term, and should be avoided. See also asthenozoospermia, oligozoospermia, and teratozoospermia


The medical term for having a very low sperm count (defined by the WHO as <20×106 spermatozoa per ml of semen).


The correct scientific term for the female gamete, often referred to as the “egg”

Oocyte retrieval

The stage in the IVF process when the oocyte, more correctly the oocyte-cumulus complex (OCC) – usually several – are aspirated from the follicles of the ovary. Sometimes referred to as “oocyte pickup” or “OPU”


The process whereby the (secondary) oocyte is released from the mature follicle on the surface of the ovary.

Polar body

A small cytoplasmic mass extruded by the oocyte during meiosis that contains a discarded set of chromosomes. The first polar body (1st PB) signals the completion of the first meiotic division and can be seen in the secondary oocyte; the second polar body (2ndPB) is extruded as a consequence of penetration of the oocyte by a spermatozoon and is an indication fertilization.


A structure formed during fertilization by the nuclear material contributed by each gamete, hence normal fertilization involves both decondensed chromatin of the sperm nucleus). A normal zygote has two pronuclei (“2PN”).


The male ejaculate, comprising spermatozoa and other cells suspended in a fluid the seminal plasma.


The correct scientific term for the male gamete, often referred to by the lay term “sperm”.


The process by which multiple follicles are stimulated to grow, using gonadotrophin hormones, in a woman’s ovaries in a single cycle so that multiple oocytes can be collected for IVF. More correctly, this process should be referred to as controlled ovarian hyperstimulation (COH).


The scientific term for a fertilized oocyte which then undergoes cleavage to form the 2-cell embryo or conceptus.