If you're having trouble getting pregnant, you're probably hearing a lot of terminology that's new to you. To help you on your pathway to pregnancy, here is a glossary of fertility terms and other terms related to infertility treatments:
Adhesion: The scar tissue that forms around reproductive organs following a previous injury, infection or surgery.
Agglutination: The occurrence of sperm clumping together, making it difficult for the sperm to easily swim.
Amenorrhea: The absence of menstrual period.
Androgen: Male sex hormones produced by the testes in the male and the ovaries and adrenal glands in the female.
Aneuploidy: A condition in which an embryo has excessive or insufficient genetic material.
Anovulation: The total absence of ovulation.
Anti-Mullerian Hormone (AMH): A hormone secreted by the small follicles on the ovary. These small follicles will eventually grow into mature follicles that will contain the egg released during ovulation. Some doctors use this test as an indication of ovarian reserve or function.
Antisperm Antibodies: Semen can cause an immune system response in either the man's or woman's body. The antibodies can damage or kill sperm. If a high number of sperm antibodies come into contact with a man's sperm, it may be hard for the sperm to fertilize an egg. A woman can have an allergic reaction to her partner's semen and make sperm antibodies.
Artificial Insemination (AI): The depositing of sperm in the vagina near the cervix or directly into the uterus, with the use of a catheter instead of by sexual intercourse.
Aspiration: Extracting through suctioning, during procedures such as egg aspiration during an in vitro fertilization (IVF) procedure, or cyst aspiration from an ovary.
Assisted Reproductive Technologies (ART): A variety of procedures used to bring about conception without sexual intercourse, including IVF, ICSI, ZIFT and GIFT.
Assisted Zona Hatching (AZH): A micromanipulation technique performed when the embryo is at Day 3 of development. An embryologist assists the embryo in breaking free of the zona pellucida thus allowing it to implant to the uterine lining. One potential explanation for failure of implantation is that the embryo is unable to escape from the zona pellucida.
Asthenospermia: Poor motility in sperm.
Azoospermia: A condition in which semen produces no sperm.
Balanced Translocation: Balanced Translocation is present if a person has the correct number of chromosomes, but their pieces are joined up incorrectly. The problem can be inherited from one parent and then balanced out by the other. If both partners have similar problems, recurrent miscarriage may occur.
Baseline Ultrasound: An examination conducted before starting therapy to determine the general position and condition of the ovaries.
Beta HCG Test: A blood test used to detect very early pregnancies and to evaluate embryonic development.
Blastocyst: An advanced embryo, approximately 5 days after fertilization, consisting of the cells that will form the fetus.
Blastocyst Transfer: IVF using an embryo that has developed for 4 or 5 days, when they reach blastocyst stage.
Blastomere: Any of the cells resulting from the cleavage of a fertilized ovum during early embryonic development.
Blighted Ovum: A pregnancy in which no fetus has developed in the pregnancy sac.
Breakthrough Bleeding: Bleeding that usually occurs during anovulatory cycles. The bleeding is due to changes in estrogen levels.
Cervical Mucus: Mucus produced by the cervix that permits passage of sperm during ovulation, and prevents infection. Mucus thins during ovulation.
Cervix: Lower section of the uterus that protrudes into the vagina, through which the sperm pass to reach the uterus.
Chemical Pregnancy: The false appearance of pregnancy due to changes in hormonal levels.
Chocolate Cyst: An ovarian cyst filled with old blood. Most commonly found when endometriosis attacks the ovary, causing it to bleed and create the cysts.
Chromosome: Contains the genetic information of an individual in the form of deoxyribonucleic acid (DNA).
Cilia: The hair-like fibers found inside the fallopian tubes. Cilia help move the egg or embryo toward the uterus.
Clomiphene Citrate: Clomiphene citrate is a drug in pill form that improves ovulation in many women with PCOS who are seeking fertility. In some patients it may given in combination with metformin. Patients who fail to conceive on clomiphene will generally benefit from treatment with gonadotropins.
Conception: Fertilization; when the sperm meets and penetrates the egg.
Controlled Ovarian Hyperstimulation: Stimulation of the ovaries with various hormonal medications in order to develop as many follicles as possible, as well as to control the timing of ovulation.
Corpus Luteum: A structure that forms at the site of an ovarian follicle after it releases an egg. The corpus luteum releases estrogen and progesterone, two hormones necessary for maintaining a pregnancy. If pregnancy occurs, the corpus luteum functions for five or six months. If pregnancy does not occur, it stops functioning.
Cryopreservation: A freezing process, at very low temperatures, used to preserve embryos, sperm and other types of tissue. Embryos not used in an ART cycle can be cryopreserved for future use.
Cytoplasm: The cell substance between the cell membrane and the nucleus, containing the cytosol, organelles, cytoskeleton, and various particles.
D&C (dilation and curettage): A surgical procedure that involves dilating the cervix to remove tissue by scraping or suctioning.
DNA (deoxyribonucleic acid): The material that makes up chromosomes and carries the genetic code.
Donor Insemination: Artificial insemination with donor sperm.
Donor Egg: Donation of an egg from one woman to another in hopes of becoming pregnant by in vitro fertilization (IVF). Also called Egg Donation.
Dyspareunia: Painful intercourse for either the man or the woman.
Dysmucorrhea: Poor quality or inadequate cervical mucus that can prohibit sperm passage.
Ectopic Pregnancy: Implantation of an embryo in a place other than the uterus. Most commonly in the fallopian tube.
Egg: The female reproductive cell. Also called ovum.
Egg Donation: Donation of an egg from one woman to another in hopes of becoming pregnant by in vitro fertilization (IVF).
Egg Donor Recipient: A woman that will obtain a pregnancy with the assistance of an egg donated from another woman.
Egg Retrieval: A procedure used to obtain eggs from ovarian follicles for use in in vitro fertilization. The procedure may be performed during laparoscopy or through the vagina by using a needle and ultrasound to locate the follicle in the ovary.
Ejaculate: The mixture of sperm and seminal fluid that comes out of a man's penis during orgasm.
Embryo: The early stages of fetal growth, from conception to the eighth week of pregnancy.
Embryo Transfer: Placing an embryo that has been created from an egg that was fertilized outside the womb into a woman's uterus or fallopian tube.
Embryologist: A specialist in embryo development.
Endometrial Biopsy (EMB): The removal of a sample of the lining of the uterus for examination. This test is performed to check for luteal phase defect (LPD).
Endometriosis: A disease whereby cells lining the uterus (or endometrium) grow outside of the uterus and stick to other organs, causing inflammation. Symptoms, if they occur, may be painful menstruation, painful bowel movements and/or painful intercourse. Infertility is an important symptom of endometriosis.
Endometrium: The lining of the uterus.
Epididymis: The organ in a man where sperm are stored, nourished and mature after production.
Epididymitis: Inflammation of the epididymis. May be a cause of male infertility.
Estradiol: The most potent naturally occurring estrogen in humans, which is released from the ovary.
Estrogen: Hormone that stimulates secondary female sexual characteristics and controls the course of the menstrual cycle. This hormone is produced in low quantities in males. Estrogen concentrations in the blood are often measured during treatment cycles.
Estrone: One of the relatively weak estrogens, which is produced in large amounts in PCOS (polycystic ovarian syndrome) patients.
Fallopian Tubes: Ducts through which eggs travel to the uterus once released from the follicle. Sperm normally meet the egg in the fallopian tube, the site at which fertilization usually occurs.
Fertility Specialist: A physician specializing in the practice of fertility. The American Board of Obstetrics and Gynecology certifies a subspecialty for OB-GYNs who receive extra training in reproductive endocrinology (the study of hormones) and infertility.
Fertility Treatment: Any method or procedure used to enhance fertility or increase the likelihood of pregnancy, such as Ovulation Induction (OI) treatment, varicocele repair (repair of varicose veins in the scrotal sac), and microsurgery to repair damaged fallopian tubes.
Fertilization: The combining of the genetic material carried by sperm and egg to create an embryo. Normally occurs inside the fallopian tube (in vivo) but may also occur in a Petri dish (in vitro). (See also In Vitro Fertilization.)
Fetus: The developing baby from the second month of pregnancy until its birth.
Fibroid: Benign (not malignant or life-threatening) tumor of fibrous tissue that can occur in the uterine wall. May be totally without symptoms or may cause abnormal menstrual patterns or infertility.
Fimbria: The finger-like extensions on the fallopian tubes that sweep the egg into the fallopian tube.
Flourescent In Situ Hybridization (FISH): A technique that uses fluorescent markers to detect changes in the genetic material.
Follicle: A fluid-filled sac in the ovary, which contain the eggs released at ovulation. Each month an egg develops inside the ovary in a follicle.
Follicular Phase: The pre-ovulation phase of a woman's cycle during which a new egg is developing within the follicle. This phase is normally between 12 and 14 days.
Follicle Stimulating Hormone (FSH): A pituitary hormone that stimulates follicular development and spermatogenesis (sperm development). Elevated FSH levels are associated with gonadal failure in both men and women.
Gamete: A reproductive cell. Sperm in men, the egg in women.
Gamete Intrafallopian Transfer (GIFT): After egg retrieval, the eggs are mixed with sperm and then placed, using a minor surgical procedure (laparoscopy), into a woman's fallopian tubes for in vivo fertilization.
Genetic Abnormalities: A genetic disorder is a disease that is caused by an abnormality in an individual's DNA. Abnormalities can range from a small mutation in a single gene to the addition or subtraction of an entire chromosome or set of chromosomes.
Gonadotropin Releasing Hormone (GnRH): A substance secreted every ninety minutes or so by a part of the brain called the hypothalamus. This hormone enables the pituitary to secrete LH and FSH, which stimulate the gonads.
Gonadotropins: Hormones secreted by the pituitary gland that control reproductive function, such as LH (luteinizing hormone) and FSH (follicle stimulating hormone).
Gonads: The organs that produce the sex cells and sex hormones. They are the testicles in men and ovaries in women.
Hormone: A chemical secreted by an endocrine gland or some nerve cells that regulates the function of a specific tissue or organ.
Hostile Mucus: The cervical mucus that hinders the natural movement of sperm through the cervical canal.
Human Chorionic Gonadotropin (HCG): The hormone produced in early pregnancy, released by the placenta after implantation, that keeps the corpus luteum producing estradiol and progesterone and thus prevent menstruation. Also used via injection to trigger ovulation after some fertility treatments, and used in men to stimulate testosterone production.
Hydrosalpinges: Abnormal distension of one or both fallopian tubes with fluid usually due to inflammation.
Hypogonadism: Inadequate ovarian or testicular function as shown by low sperm production or lack of follicle production, as well as low or absent levels of FSH and LH.
Hysterosalpingogram (HSG): An x-ray procedure in which a special liquid is injected through the cervix into the uterine cavity to illustrate the inner shape of the uterus and degree of openness of the fallopian tubes. If the tubes are open, the liquid will spill out the ends of the tubes. If the tubes are blocked, the liquid is trapped.
Hyperstimulation: A reaction to the more powerful fertility medications caused by excessive stimulation of the ovaries. It causes the ovaries to enlarge and create an overabundance of eggs.
Hysteroscopy: A visual examination of the uterus using an instrument called a hysteroscope, which enables the doctor to see into the organ without making a large incision.
Hysterosonogram (HSN): An office based Ultrasound procedure performed around day 7 to 10 of your menstrual cycle. This test is will provide detailed images of the uterus, endometrial lining and ovaries. This test is most often used to identify fibroids, polyps, scar tissue, uterine adhesions or uterine defects that may interfere with pregnancy.
Idiopathic Infertility: The term used to explain when the cause of infertility cannot be explained.
Implantation (Embryo): The embedding of the embryo into tissue so it can establish contact with the mother's blood supply for nourishment. Implantation usually occurs in the lining of the uterus; however, in an ectopic pregnancy it may occur elsewhere in the body.
In Vitro Fertilization (IVF): The procedure where eggs are removed from the ovaries and mixed with sperm. Eggs that fertilize become embryos and are transferred to the uterus in hopes that a pregnancy will result.
Infertility: The inability to conceive after a year of unprotected intercourse (six months if a woman is over age 35).
Intracytoplasmic Sperm Injection (ICSI): A micromanipulation (occurring under the microscope) procedure in which a single sperm is injected directly into the egg to enable fertilization with very low sperm counts or with non-motile sperm (sperm that don't swim effectively toward the egg). The embryo is then transferred to the uterus.
Intramuscular Needle: A needle designed to administer medication deep into the muscle. Injections of this type are usually given in the thigh or upper buttock area.
Intrauterine Insemination (IUI): A procedure in which the sperm is placed directly into the uterus using a catheter.
Klinefelter's Syndrome: A genetic abnormality that may cause infertility. It is characterized by having two X chromosomes and one Y chromosome.
Laparoscopy: Examination of the pelvic region by using a small telescope called a laparoscope.
Luteal Phase: Days of the menstrual cycle after ovulation when progesterone is produced by the corpus luteum.
Luteinizing Hormone (LH): A pituitary hormone that stimulates the gonads. In a man, LH is necessary for spermatogenesis and for the production of testosterone. In a woman, LH is necessary for the production of estrogen.
Luteinizing Hormone Surge: The release of luteinizing hormone (LH) that causes release of a mature egg from the follicle.
Luteal Phase: The portion of a menstrual cycle before menstruation, but after ovulation. A normal luteal phase lasts approximately 10 to 16 days. This is the part of the cycle that releases progesterone and enables implantation of the pre-embryo, which may result in pregnancy.
Luteal Phase Defect (LPD): When the lining of the uterus does not develop properly, making it unsuitable for implantation.
Menopause: Menopause is a natural biological process that signals the permanent end of menstruation and fertility, defined as occurring 12 months after your last menstrual period.
Menstruation: Shedding of the uterine lining by bleeding indicating that pregnancy has not taken place: normally occurs about once a month in the mature female.
Metformin: Metformin is the most commonly used insulin sensitizer drug in PCOS. It is used to improve ovulation, either given by itself or more commonly in combination with clomiphene citrate. In some patients with a severe degree of insulin resistance and/or a strong family history of diabetes, metformin used long-term may be used to reduce the chance of developing diabetes and other related problems.
Micro Epididymal Sperm aspiration (MESA): A way of obtaining sperm in those men with a reproductive tract blockage (i.e., after a vasectomy, congenital absence of the vas deferens). A 1/2 inch incision made in the scrotal skin to isolate the epididymis. A microscope is used to examine the tubules of the epididymis that contain the sperm. All of the sperm containing fluid is collected and taken to the IVF lab for processing, use and freezing.
Micromanipulation: A variety of techniques that can be performed in a laboratory under a microscope. An embryologist manipulates egg and sperm to improve the chances of pregnancy. (See also Intracytoplasmic Sperm Injection, ICSI.)
Miscarriage: An involuntary ending of a pregnancy.
Morphology: The physical structure and configuration of sperm cells.
Motility: The ability of sperm to swim. Poor motility means the sperm have a difficult time swimming toward the egg.
Myoma (fibroid or leiomyoma): A non-cancerous, benign tumor of the uterine muscle and connective tissue.
Myomectomy: A surgical procedure used to remove a fibroid tumor from the uterus, leaving the uterus intact.
Occlusion: A blockage. If fallopian tubes are occluded, it means they are blocked.
Oligomenorrhea: Irregular menstrual periods.
Oligospermia: Low number of sperm in the ejaculate of the male.
Oocyte: Another name for an egg cell or female gamete.
Ovarian Failure: The failure of the ovary to respond to FSH stimulation from the pituitary because of damage to or malformation of the ovary, or a chronic disease such as autoimmune disease. Diagnosed by elevated FSH in the blood.
Ovarian Hyperstimulation Syndrome (OHSS): Sudden ovarian enlargement accompanied by fluid accumulation in the abdominal cavity. This may occur with or without pain, and with or without accumulation of fluid in the lungs. OHSS is caused when the ovaries become over stimulated by the various hormones that cause follicular development.
Ovarian Stimulation: During a typical menstrual cycle, one egg matures and is released during ovulation. In order to increase the chances of creating a viable embryo and a successful pregnancy, a woman's ovaries will be stimulated with hormones to increase the number of eggs released.
Ovaries: The two sexual glands of the female where the eggs are stored. The ovaries also produce the hormones estrogen and progesterone.
Ovulation: The release of the egg (ovum) from the ovarian follicle.
Ovulation Induction (OI): Medical treatment performed to initiate ovulation.
Ovulatory Dysfunction: A problem with the ovary where the egg is not matured or released properly.
Ovum: An egg cell.
Pelvic Inflammatory Disease (PID): Inflammatory disease of the pelvis (usually caused by infection) that can lead to scarring and infertility.
Percutaneous Epididymal Sperm Aspiration (PESA): A needle is placed into the epididymis where a pocket of sperm will be found and aspirated.
Pituitary Gland: The gland located at the base of the brain that secretes a number of important hormones that regulate fertility, as well as normal growth and development of the body.
Polycystic Ovarian Syndrome (PCOS): Also called Stein-Leventhal syndrome. The formation of cysts in the ovaries that occurs when the follicle stops developing. This is due to a hormonal imbalance in the ovary. A reason for infertility caused by an overabundance of androgens, small cysts on the ovaries, and lack of ovulation. Symptoms may include obesity or weight gain, acne, excessive hair growth and amenorrhea. PCO may also occur without outward symptoms.
Polymere Chain Reaction (PCR): A technique in molecular genetics that permits the analysis of any short sequence of DNA (or RNA) even in samples containing only minute quantities of DNA or RNA. PCR is used to reproduce (amplify) selected sections of DNA or RNA for analysis.
Preimplantation Embryo: Preimplantation embryo development involves four stages: fertilization, cell cleavage, morula and blastocyst formation.
Preimplantation Genetic Diagnosis (PGD): The process of taking a single cell, or blastomere, from a developing embryo and testing it for genetic disease or chromosomal abnormality such as cystic fibrosis or Down syndrome.
Primary Infertility: Women who have never conceived before or the inability to ever carry a pregnancy to term.
Progesterone: A hormone found in men and women. In women the hormone produced by the corpus luteum during the second half of a woman's cycle. It thickens the lining of the uterus to prepare it to accept implantation of a fertilized egg.
Prolactin: Prolactin is a chemical that is secreted by your pituitary gland. This is the pea-sized gland found in the middle of your brain, which is responsible for triggering many of your body's processes.
Prostate: The gland in the male that supplies some of the seminal fluid, and prepares the urethra for the passage of sperm.
Recombinant Human DNA (r-hDNA) Technology: DNA that has been modified so that it contains genes from two different sources. Recombinant technology is often used to produce medications with a higher degree of purity and higher quality control.
Reproductive Endocrinologist: An Obstetrician-Gynecologist with advanced education, research and professional skills in Reproductive Endocrinology & Infertility. These highly trained and qualified physicians treat reproductive disorders that affect children, women, men, the mature woman, and infertility in both men and women.
Retrograde Ejaculation: Semen flows backwards into the bladder instead of forward through the urethra. It is a cause of male infertility.
Scrotum: The pouch at the base of the penis that contains the testicles.
Secondary Infertility: Infertility of six months or more in a couple that has previously had a child.
Semen: The fluid that is secreted from the testicles, seminal vesicles and prostate during ejaculation.
Semen Analysis: Examination of semen for quality. To view an example of a semen analysis form, click here
Seminal Vesicles: The pair of pouch-like glands around the prostate that produce the milky fluid that mixes with the sperm prior to ejaculation.
Seminiferous Tubules: The tubes found in the testicles that produce sperm.
Septate Uterus: A uterine abnormality dividing the uterus into two halves by a septum.
Septum: The abnormal tissue that divides the uterus in half.
Sertoli Cell: The cells found in the testes that assist in sperm cell production.
Sexually Transmitted Disease (STDs): Any disease transmitted by sexual contact; caused by microorganisms that survive on the skin or mucus membranes of the genital area; or transmitted via semen, vaginal secretions, or blood during intercourse. AIDS, chlamydia, genital herpes, genital warts, gonorrhea, syphilis, yeast infections, and some forms of hepatitis.
Shared IVF Success Program: These funds can be used to pursue other options, such as adoption, if a successful pregnancy is not achieved through IVF. Not all patients are candidates for this program and cases are reviewed on an individual basis.
Sonogram: Used to reveal images of internal organs by using high-frequency sound waves. In fertility treatment it helps to monitor follicular growth and to detect abnormalities such as cysts. This procedure is also known as ultrasound.
Sperm (spermatozoa): The microscopic cell that carries the male's genetic information to the female's egg; the male reproductive cell; the male gamete.
Sperm Bank: A place where sperm is collected and frozen to be used at a later time by a couple or to be donated for use in assisted reproductive technologies (ARTs).
Sperm count: The number of sperm in an ejaculate. Given as the number of sperm per milliliter.
Sperm Density: The number of sperm per milliliter or cc. Sperm may be measured by its motility, morphology, count and viability.
Sperm Morphology: The shape and form of each sperm.
Sperm Motility: The percentage of sperm moving forward.
Sperm Viability: Refers to whether or not the sperm is alive.
Sperm Washing: Technique that is used to separate the seminal fluid from the sperm.
Spermatocyte: Sperm cell that is immature.
Spermatogenesis: The production of sperm.
Spermatozoa: The male reproductive cell or gamete. Also called sperm.
Stein-Leventhal Syndrome (PCOS): The formation of cysts in the ovaries that occurs when the follicle stops developing. This is due to a hormonal imbalance in the ovary. A reason for infertility caused by an overabundance of androgens, small cysts on the ovaries, and lack of ovulation. Symptoms may include obesity or weight gain, acne, excessive hair growth and amenorrhea. PCO may also occur without outward symptoms.
Sterility: An irreversible condition that prevents conception.
Subcutaneous Injection: Administration of medication with a fine small needle just below the surface of the skin, into fatty tissue.
Surrogacy: A woman who agrees to become impregnated and carry a baby for another woman. This can be done using the sperm of the male and the egg of the female. It may also be performed using both donor sperm and eggs.
Teratospermia: Condition characterised by the presence of malformed spermatozoa in the semen.
Testes: The two male sexual glands that produce sperm as well as the male hormone testosterone.
Testicle: The gonad of the male producing sperm and male sex hormones.
Testicular Biopsy: The surgical removal of testicular tissue to determine if the cells have the ability to produce normal sperm, or to diagnose possible neoplasms.
Testicular/Epidydimal Sperm Aspiration (TESA): A needle biopsy of the testicle. It is an office procedure performed under local anesthesia. A small incision is made in the scrotal skin and a spring loaded needle is used to collect tissue from the testicle.
Testicular Failure: Occurs when the testes do not produce a normal number of mature sperm and when the hormones needed for normal sperm are abnormally elevated.
Testicular Torsion: A disorder where the testicle twists on itself, cutting off its own blood supply.
Testosterone: The male hormone responsible for the formation of secondary sex characteristics and for supporting the sex drive. Testosterone is also necessary for spermatogenesis (sperm development).
Thromboembolism: Obstruction of a blood vessel with material carried by the blood stream from the site of origin to plug another vessel.
Thyroid Stimulating Hormone (TSH): TSH is produced by the pituitary gland and tells the thyroid gland to make and release the hormones thyroxine (T4) and triiodothyronine (T3).
Transvaginal Oocyte Retrieval: Technique used in in vitro fertilization in order to remove oocytes from the ovary of the female, enabling fertilization outside the body.
Transvaginal Ultrasound Aspiration: The technique used in in vitro fertilization (IVF) to retrieve or aspirate the eggs.
Tubal Ligation: A procedure to surgically tie or obstruct the fallopian tubes in order to sterilize a woman.
Tubal pregnancy: The development and attachment of a fertilized egg in a fallopian tube.
Tuboplasty: Reconstructive surgery to correct any abnormality of the fallopian tubes causing infertility.
Turner's Syndrome: A genetic abnormality in females where a chromosome is missing, causing no ovarian function.
Ultrasound: A test using high frequency sound waves to visualize the ovaries, uterus, and developing fetus.
Uterus: Hollow muscular organ where the fetus grows until birth.
Vagina: Muscular opening in a woman extending from the vulva to the cervix of the uterus.
Varicocele: Varicose veins in the testicle that can cause sperm abnormalities.
Vas deferens: The pair of tubes in the male that lead from the epididymis to the ejaculatory duct in the prostate.
Vasectomy: Male surgical sterilization by tying the vas deferens.
Vitrification: Vitrification comes from the Latin meaning "to turn into glass." It is the process by which eggs are rapidly cooled at a rapid rate. This rapid cooling prevents the formation of ice crystals within the egg.
ZIFT (zygote intrafallopian transfer): A form of in vitro fertilization (IVF) where the fertilized egg is placed into the fallopian tube.
Zona Pellucida: The protective coating surrounding the egg that protects the growing embryo until approximately 5 days after fertilization, where then the zona pellucid will break down and allow the embryo to implant in the uterine lining for proper fetal development.
Zygote: A fertilized egg that was created when two haploid cells-usually an ovum from a female and a sperm cell from a male-merge into a single diploid cell.