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in human reproduction, the process by which the male's sperm unites with the female's oocyte, creating a new life. The sex and other biologic traits of the new individual are determined by the combined genes and chromosomes that exist in the sperm and oocyte. See also conception and reproduction. Called also fecundation and impregnation.

After injection into the vagina, millions of sperm cells (spermatozoa) make use of their whiplike tails to swim through the cervix toward the uterus. Most are destroyed along the way by secretions in the vagina, but some reach the uterus and a few may enter the fallopian tubes. A very small number may survive as long as 48 hours. If during this period only one sperm succeeds in entering a fallopian tube and meeting there an oocyte ready to be fertilized, conception can occur. This event is possible only during a period of about 4 days of the month. After the sperm lodges in the oocyte, the tail disappears, but the head unites with the oocyte to form the zygote.
in vitro fertilization the process by which conception takes place in a laboratory medium; the term literally means fertilization “in glass.” A lay term for the product of in vitro fertilization is “test tube baby.”

The treatment cycle involves the following steps: (1) Induction of ovulation with fertility drugs, such as clomiphene citrate, injectable follicle-stimulating hormone/luteinizing hormone, or both, to produce multiple ovarian follicles. When the largest follicle reaches 20 mm in diameter the patient is given an injection of human chorionic gonadotropin to induce expulsion of the oocyte from the follicle. (2) Laparoscopy and follicular aspiration for the harvesting of oocytes. (3) Maturation of retrieved oocytes and inoculation with the husband's or donor's sperm. (4) Incubation of the resulting embryos until they reach the two- to six-cell stage. (5) Transfer of an embryo via catheter into the patient's uterus; at this point intensive intervention ceases, the pregnancy is considered normal, and no further manipulation is required.
in vivo fertilization union of the sperm and ovum within the reproductive tract of the female; usually taken to mean artificial insemination in which the sperm is artificially introduced into the vagina, cervix, or uterine cavity to overcome the problem of infertility.


The process beginning with penetration of the secondary oocyte by the sperm and completed by fusion of the male and female pronuclei.


/fer·ti·li·za·tion/ (fer″tĭ-lĭ-za´shun) impregnation; union of male and female gametes to form the diploid zygote, leading to development of a new individual.
external fertilization  union of the gametes outside the bodies of the originating organisms, as in most fish.
internal fertilization  union of the gametes inside the body of the female, the sperm having been transferred from the body of the male by an accessory sex organ or other means.
in vitro fertilization  removal of a secondary oocyte, fertilization of it in a culture medium in the laboratory, and placement of the dividing zygote into the uterus.


1. The act or process of initiating biological reproduction by insemination or pollination.
2. The union of male and female gametes to form a zygote.
3. The act or process of applying a fertilizer.

fer′til·i·za′tion·al adj.


Etymology: L, fertilis, fruitful
the union of male and female gametes to form a zygote from which the embryo develops. The process usually takes place in the outer one third of the fallopian tube of the female when a spermatozoon, carried in the seminal fluid discharged during coitus, comes in contact with and penetrates the ovum. Rapid chemical changes in the membrane of the ovum prevent the entrance of additional spermatozoa. Penetration by the spermatozoon stimulates the completion of the second meiotic division and formation of the pronucleus in the ovum. Fusion and synapsis of the male and female pronuclei restore the diploid number of chromosomes to the germ cell, thereby determining the sex of the zygote and the characteristics inherited from each parent and stimulating the initiation of development through cleavage. Kinds of fertilization include cross-fertilization, external fertilization, and internal fertilization. See also in vitro fertilization, oogenesis, spermatogenesis.
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Fertilized human egg
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Fertilization cycle


Fusion of ovum & spermatozoon Reproduction medicine The penetration of an egg by sperm, resulting in combined genetic material that develops into an embryo


The process beginning with penetration of the secondary oocyte by the sperm and completed by fusion of the male and female pronuclei.


(fert?il-i-za'shon) [L. fertilis, reproductive]
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The process that begins with the penetration of the secondary oocyte by the spermatozoon and is completed with the fusion of the male and female pronuclei. This usually takes place in the fallopian tube. Viable spermatozoa have been found in the tube 48 hr after the last coitus. After the ovum is fertilized and the diploid chromosome number is restored in the zygote, cell division begins. The blastocyst then enters the uterus, where it may implant for continued nurture and development. See: illustration

heterologous fertilization

Assisted fertilization of a woman's ova with donor sperm.
See: in vitro fertilization; artificial insemination

homologous fertilization

Artificial fertilization of a woman's ovum by her husband's sperm. The ovum and sperm are united while both are outside the body and then are placed in the uterus during the optimum time for fertilization.

in vitro fertilization

Abbreviation: IVF
Laboratory-produced conception, used to enable pregnancy in infertile women when sperm access to ova is prevented by structural defects in the fallopian tubes or other factors, or in combination with her partner's sterility. After drug-induced follicle maturation, a sample of ova and follicular fluid is removed surgically and mixed with a specimen of the partner's sperm for incubation. The resulting zygote is introduced into the woman's uterus for implantation.
See: embryo transfer; GIFT; ZIFTillustration


The union of the spermatozoon with the egg (ovum) so that the full complement of chromosomes is made up and the process of cell division, to form a new individual, started.


the fusion of male and female GAMETES to give rise to a ZYGOTE which then subsequently develops into a new organism. See ACROSOME for further details of animal fertilization. See EMBRYO SAC for details of the ‘double’ fertilization of flowering plants.


The joining of the sperm and the egg; conception.
Mentioned in: Contraception


Process beginning with penetration of secondary oocyte by one or more sperm(s) and completed by fusion of the male and female pronuclei.


in animal reproduction, the process by which the spermatozoon unites with the ovum. By this event, also called conception, the male and female gametes unite to form a single-celled zygote. When one spermatozoon penetrates the ovum a reaction occurs which prevents any further spermatozoa entering. The nuclei of the spermatozoon and the ovum fuse in a process called syngamy and fertilization is complete.
Spermatozoa lodged in the female reproductive tract maintain their fertility for 5 days in mares, up to 90 hours in bitches and for 24 to 48 hours in cow, ewe, sow. In the female, the ovulated ovum remains viable in the tract for 12 to 18 hours.
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Fertilization. By permission from Aspinall V, O'Reilly M, Introduction to Veterinary Anatomy and Physiology, Butterworth Heinemann, 2004

in vitro fertilization
union of male and female germ cells outside the body, in an artificial environment.

Patient discussion about fertilization

Q. i just have my period last november 25 and ended on 28.when is my possible fertile and ovulation period please help me identify my fertile and ovulation period

A. If someone knew it, it'd solve the human race many problems with fertility. The problem is that ovulation (and thus, the period of possible fertility) happens 14 days BEFORE the onset of menses, so you know about it only retrospectively.

However there ways such as serial body temperature measuring, along with kits that measures the level of hormones in the urine in order to estimate the time of the coming ovulation, and help in timing intercourse.

You may read more about it here (www.mayoclinic.com/health/ovulation-signs/AN01521 ) but anyway, consulting a doctor (e.g. gynecologist) may be wise.

More discussions about fertilization
References in periodicals archive ?
He said that since they are conducting in vitro fertilizations without interference or control from males or females, this provides clear evidence that eggs favour the sperm of their own species, but only when given a choice.
He said that they found that the egg itself plays no significant role in promoting fertilization precedence by their own species' sperm and instead it is actually the ovarian fluid that controls which species' sperm wins the fertilizations, which was unexpected.
ABSTRACT To obtain the highest yield during in vitro fertilization of tropical abalone Haliotis asinina, optimal proportion of the gametes, the timing of sperm egg interaction, and subsequent development were investigated.
KEY WORDS: abalone, Haliotis asinina, sperm, egg, fertilization, early development
At the time, ice-core records suggested that during past glacial periods, naturally occurring iron fertilization had repeatedly drawn as much as 60 billion tons of carbon out of the atmosphere.
But economists conclude that the growing urgency to solve our emissions problem will reward anyone who can make iron fertilization work.
The Japan Society of Obstetrics and Gynecology said Monday it will take action, including possible expulsion, against a doctor who conducted extra-marital fertilization procedures.
The society's move follows a news report that Yahiro Netsu, director of a maternity clinic in Nagano Prefecture, used the eggs of a 30-year-old woman's younger sister to perform in vitro fertilization using sperm from the woman's husband.
Over the course of the study, the researchers found 198 pregnancies by testing for the level of human chorionic gonadotropin (hCG), a hormone produced by an egg about one week after fertilization.
Most of the ocean food chain is too small to see, but that doesn't mean the effects of iron fertilization will be, too.
This study documents another example of assortative fertilization by genome in situ hybridization in reciprocal crosses of scallops Chlamys farreri and Patinopecten yessoensis.
Among many differences between natural and intentional iron fertilizations, the most striking was the bottom line: Natural fertilization was 10 to 100 times more efficient at removing carbon from the surface ocean than any artificial experiment has been.