Birth Rate: The number of births in a given population per year or other unit of time.Live Birth: The event that a FETUS is born alive with heartbeats or RESPIRATION regardless of GESTATIONAL AGE. Such liveborn is called a newborn infant (INFANT, NEWBORN).Pregnancy: The status during which female mammals carry their developing young (EMBRYOS or FETUSES) in utero before birth, beginning from FERTILIZATION to BIRTH.Birth Weight: The mass or quantity of heaviness of an individual at BIRTH. It is expressed by units of pounds or kilograms.Premature Birth: CHILDBIRTH before 37 weeks of PREGNANCY (259 days from the first day of the mother's last menstrual period, or 245 days after FERTILIZATION).Pregnancy in Adolescence: Pregnancy in human adolescent females under the age of 19.Pregnancy Rate: The ratio of the number of conceptions (CONCEPTION) including LIVE BIRTH; STILLBIRTH; and fetal losses, to the mean number of females of reproductive age in a population during a set time period.Pregnancy Outcome: Results of conception and ensuing pregnancy, including LIVE BIRTH; STILLBIRTH; SPONTANEOUS ABORTION; INDUCED ABORTION. The outcome may follow natural or artificial insemination or any of the various ASSISTED REPRODUCTIVE TECHNIQUES, such as EMBRYO TRANSFER or FERTILIZATION IN VITRO.Embryo Transfer: The transfer of mammalian embryos from an in vivo or in vitro environment to a suitable host to improve pregnancy or gestational outcome in human or animal. In human fertility treatment programs, preimplantation embryos ranging from the 4-cell stage to the blastocyst stage are transferred to the uterine cavity between 3-5 days after FERTILIZATION IN VITRO.Fertilization in Vitro: An assisted reproductive technique that includes the direct handling and manipulation of oocytes and sperm to achieve fertilization in vitro.Illegitimacy: The state of birth outside of wedlock. It may refer to the offspring or the parents.Infant, Low Birth Weight: An infant having a birth weight of 2500 gm. (5.5 lb.) or less but INFANT, VERY LOW BIRTH WEIGHT is available for infants having a birth weight of 1500 grams (3.3 lb.) or less.Infant, Newborn: An infant during the first month after birth.Multiple Birth Offspring: The offspring in multiple pregnancies (PREGNANCY, MULTIPLE): TWINS; TRIPLETS; QUADRUPLETS; QUINTUPLETS; etc.Reproductive Techniques, Assisted: Clinical and laboratory techniques used to enhance fertility in humans and animals.Maternal Age: The age of the mother in PREGNANCY.Pregnancy, Multiple: The condition of carrying two or more FETUSES simultaneously.Birth Certificates: Official certifications by a physician recording the individual's birth date, place of birth, parentage and other required identifying data which are filed with the local registrar of vital statistics.Ovulation Induction: Techniques for the artifical induction of ovulation, the rupture of the follicle and release of the ovum.Oocyte Retrieval: Procedures to obtain viable OOCYTES from the host. Oocytes most often are collected by needle aspiration from OVARIAN FOLLICLES before OVULATION.Sperm Injections, Intracytoplasmic: An assisted fertilization technique consisting of the microinjection of a single viable sperm into an extracted ovum. It is used principally to overcome low sperm count, low sperm motility, inability of sperm to penetrate the egg, or other conditions related to male infertility (INFERTILITY, MALE).Vital Statistics: Used for general articles concerning statistics of births, deaths, marriages, etc.Infertility, Female: Diminished or absent ability of a female to achieve conception.Embryo Implantation: Endometrial implantation of EMBRYO, MAMMALIAN at the BLASTOCYST stage.Infertility: Inability to reproduce after a specified period of unprotected intercourse. Reproductive sterility is permanent infertility.Cryopreservation: Preservation of cells, tissues, organs, or embryos by freezing. In histological preparations, cryopreservation or cryofixation is used to maintain the existing form, structure, and chemical composition of all the constituent elements of the specimens.Reproductive Control Agents: Substances used either in the prevention or facilitation of pregnancy.Follicle Stimulating Hormone, Human: A major gonadotropin secreted by the human adenohypophysis (PITUITARY GLAND, ANTERIOR). Follicle-stimulating hormone stimulates GAMETOGENESIS and the supporting cells such as the ovarian GRANULOSA CELLS, the testicular SERTOLI CELLS, and the LEYDIG CELLS. FSH consists of two noncovalently linked subunits, alpha and beta. The alpha subunit is common in the three human pituitary glycoprotein hormones (TSH, LH, and FSH), but the beta subunit is unique and confers its biological specificity.Abortion, Spontaneous: Expulsion of the product of FERTILIZATION before completing the term of GESTATION and without deliberate interference.Gamete Intrafallopian Transfer: A technique that came into use in the mid-1980's for assisted conception in infertile women with normal fallopian tubes. The protocol consists of hormonal stimulation of the ovaries, followed by laparoscopic follicular aspiration of oocytes, and then the transfer of sperm and oocytes by catheterization into the fallopian tubes.Single Embryo Transfer: The techniques used to select and/or place only one embryo from FERTILIZATION IN VITRO into the uterine cavity to establish a singleton pregnancy.Gestational Age: The age of the conceptus, beginning from the time of FERTILIZATION. In clinical obstetrics, the gestational age is often estimated as the time from the last day of the last MENSTRUATION which is about 2 weeks before OVULATION and fertilization.Clomiphene: A triphenyl ethylene stilbene derivative which is an estrogen agonist or antagonist depending on the target tissue. Note that ENCLOMIPHENE and ZUCLOMIPHENE are the (E) and (Z) isomers of Clomiphene respectively.Birth Order: The sequence in which children are born into the family.Cesarean Section: Extraction of the FETUS by means of abdominal HYSTEROTOMY.Infant Mortality: Postnatal deaths from BIRTH to 365 days after birth in a given population. Postneonatal mortality represents deaths between 28 days and 365 days after birth (as defined by National Center for Health Statistics). Neonatal mortality represents deaths from birth to 27 days after birth.Fertility Agents, Female: Compounds which increase the capacity to conceive in females.Abortion, Habitual: Three or more consecutive spontaneous abortions.Abortion, Legal: Termination of pregnancy under conditions allowed under local laws. (POPLINE Thesaurus, 1991)Pregnancy Complications: Conditions or pathological processes associated with pregnancy. They can occur during or after pregnancy, and range from minor discomforts to serious diseases that require medical interventions. They include diseases in pregnant females, and pregnancies in females with diseases.Insemination, Artificial, Homologous: Human artificial insemination in which the husband's semen is used.Fertility: The capacity to conceive or to induce conception. It may refer to either the male or female.Delivery, Obstetric: Delivery of the FETUS and PLACENTA under the care of an obstetrician or a health worker. Obstetric deliveries may involve physical, psychological, medical, or surgical interventions.National Center for Health Statistics (U.S.): A center in the PUBLIC HEALTH SERVICE which is primarily concerned with the collection, analysis, and dissemination of health statistics on vital events and health activities to reflect the health status of people, health needs, and health resources.Embryo Culture Techniques: The technique of maintaining or growing mammalian EMBRYOS in vitro. This method offers an opportunity to observe EMBRYONIC DEVELOPMENT; METABOLISM; and susceptibility to TERATOGENS.United StatesSingle Parent: A natural, adoptive, or substitute parent of a dependent child, who lives with only one parent. The single parent may live with or visit the child. The concept includes the never-married, as well as the divorced and widowed.Paternal Age: Age of the biological father.Prenatal Care: Care provided the pregnant woman in order to prevent complications, and decrease the incidence of maternal and prenatal mortality.Twins: Two individuals derived from two FETUSES that were fertilized at or about the same time, developed in the UTERUS simultaneously, and born to the same mother. Twins are either monozygotic (TWINS, MONOZYGOTIC) or dizygotic (TWINS, DIZYGOTIC).Cleavage Stage, Ovum: The earliest developmental stage of a fertilized ovum (ZYGOTE) during which there are several mitotic divisions within the ZONA PELLUCIDA. Each cleavage or segmentation yields two BLASTOMERES of about half size of the parent cell. This cleavage stage generally covers the period up to 16-cell MORULA.Nafarelin: A potent synthetic agonist of GONADOTROPIN-RELEASING HORMONE with 3-(2-naphthyl)-D-alanine substitution at residue 6. Nafarelin has been used in the treatments of central PRECOCIOUS PUBERTY and ENDOMETRIOSIS.Sex Ratio: The number of males per 100 females.Fetal Mortality: Number of fetal deaths with stated or presumed gestation of 20 weeks or more in a given population. Late fetal mortality is death after of 28 weeks or more.Retrospective Studies: Studies used to test etiologic hypotheses in which inferences about an exposure to putative causal factors are derived from data relating to characteristics of persons under study or to events or experiences in their past. The essential feature is that some of the persons under study have the disease or outcome of interest and their characteristics are compared with those of unaffected persons.Minors: A person who has not attained the age at which full civil rights are accorded.Parental Notification: Reporting to parents or guardians about care to be provided to a minor (MINORS).Cohort Studies: Studies in which subsets of a defined population are identified. These groups may or may not be exposed to factors hypothesized to influence the probability of the occurrence of a particular disease or other outcome. Cohorts are defined populations which, as a whole, are followed in an attempt to determine distinguishing subgroup characteristics.Abortion, Induced: Intentional removal of a fetus from the uterus by any of a number of techniques. (POPLINE, 1978)Oocyte Donation: Transfer of preovulatory oocytes from donor to a suitable host. Oocytes are collected, fertilized in vitro, and transferred to a host that can be human or animal.Fetal Death: Death of the developing young in utero. BIRTH of a dead FETUS is STILLBIRTH.Menotropins: Extracts of urine from menopausal women that contain high concentrations of pituitary gonadotropins, FOLLICLE STIMULATING HORMONE and LUTEINIZING HORMONE. Menotropins are used to treat infertility. The FSH:LH ratio and degree of purity vary in different preparations.Marital Status: A demographic parameter indicating a person's status with respect to marriage, divorce, widowhood, singleness, etc.Birth Intervals: The lengths of intervals between births to women in the population.Insemination, Artificial: Artificial introduction of SEMEN or SPERMATOZOA into the VAGINA to facilitate FERTILIZATION.Blastocyst: A post-MORULA preimplantation mammalian embryo that develops from a 32-cell stage into a fluid-filled hollow ball of over a hundred cells. A blastocyst has two distinctive tissues. The outer layer of trophoblasts gives rise to extra-embryonic tissues. The inner cell mass gives rise to the embryonic disc and eventual embryo proper.Stillbirth: The event that a FETUS is born dead or stillborn.Parturition: The process of giving birth to one or more offspring.Anovulation: Suspension or cessation of OVULATION in animals or humans with follicle-containing ovaries (OVARIAN FOLLICLE). Depending on the etiology, OVULATION may be induced with appropriate therapy.Preimplantation Diagnosis: Determination of the nature of a pathological condition or disease in the OVUM; ZYGOTE; or BLASTOCYST prior to implantation. CYTOGENETIC ANALYSIS is performed to determine the presence or absence of genetic disease.Parity: The number of offspring a female has borne. It is contrasted with GRAVIDITY, which refers to the number of pregnancies, regardless of outcome.Obstetric Labor, Premature: Onset of OBSTETRIC LABOR before term (TERM BIRTH) but usually after the FETUS has become viable. In humans, it occurs sometime during the 29th through 38th week of PREGNANCY. TOCOLYSIS inhibits premature labor and can prevent the BIRTH of premature infants (INFANT, PREMATURE).Family Planning Policy: A course or method of action selected, usually by a government, to guide and determine present and future decisions on population control by limiting the number of children or controlling fertility, notably through family planning and contraception within the nuclear family.Demography: Statistical interpretation and description of a population with reference to distribution, composition, or structure.Sperm Retrieval: Procedures to obtain viable sperm from the male reproductive tract, including the TESTES, the EPIDIDYMIS, or the VAS DEFERENS.Fallopian Tube Diseases: Diseases involving the FALLOPIAN TUBES including neoplasms (FALLOPIAN TUBE NEOPLASMS); SALPINGITIS; tubo-ovarian abscess; and blockage.Immunity, Herd: The non-susceptibility to infection of a large group of individuals in a population. A variety of factors can be responsible for herd immunity and this gives rise to the different definitions used in the literature. Most commonly, herd immunity refers to the case when, if most of the population is immune, infection of a single individual will not cause an epidemic. Also, in such immunized populations, susceptible individuals are not likely to become infected. Herd immunity can also refer to the case when unprotected individuals fail to contract a disease because the infecting organism has been banished from the population.Labor, Induced: Artificially induced UTERINE CONTRACTION. Generally, LABOR, OBSTETRIC is induced with the intent to cause delivery of the fetus and termination of pregnancy.Hispanic Americans: Persons living in the United States of Mexican (MEXICAN AMERICANS), Puerto Rican, Cuban, Central or South American, or other Spanish culture or origin. The concept does not include Brazilian Americans or Portuguese Americans.Birth Injuries: Mechanical or anoxic trauma incurred by the infant during labor or delivery.Reproductive Techniques: Methods pertaining to the generation of new individuals, including techniques used in selective BREEDING, cloning (CLONING, ORGANISM), and assisted reproduction (REPRODUCTIVE TECHNIQUES, ASSISTED).Risk Factors: An aspect of personal behavior or lifestyle, environmental exposure, or inborn or inherited characteristic, which, on the basis of epidemiologic evidence, is known to be associated with a health-related condition considered important to prevent.Azoospermia: A condition of having no sperm present in the ejaculate (SEMEN).Age Factors: Age as a constituent element or influence contributing to the production of a result. It may be applicable to the cause or the effect of a circumstance. It is used with human or animal concepts but should be differentiated from AGING, a physiological process, and TIME FACTORS which refers only to the passage of time.Congenital Abnormalities: Malformations of organs or body parts during development in utero.Family Planning Services: Health care programs or services designed to assist individuals in the planning of family size. Various methods of CONTRACEPTION can be used to control the number and timing of childbirths.Ovarian Hyperstimulation Syndrome: A complication of OVULATION INDUCTION in infertility treatment. It is graded by the severity of symptoms which include OVARY enlargement, multiple OVARIAN FOLLICLES; OVARIAN CYSTS; ASCITES; and generalized EDEMA. The full-blown syndrome may lead to RENAL FAILURE, respiratory distress, and even DEATH. Increased capillary permeability is caused by the vasoactive substances, such as VASCULAR ENDOTHELIAL GROWTH FACTORS, secreted by the overly-stimulated OVARIES.Infant, Premature: A human infant born before 37 weeks of GESTATION.Treatment Outcome: Evaluation undertaken to assess the results or consequences of management and procedures used in combating disease in order to determine the efficacy, effectiveness, safety, and practicability of these interventions in individual cases or series.Prospective Studies: Observation of a population for a sufficient number of persons over a sufficient number of years to generate incidence or mortality rates subsequent to the selection of the study group.Seasons: Divisions of the year according to some regularly recurrent phenomena usually astronomical or climatic. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Chorionic Gonadotropin: A gonadotropic glycoprotein hormone produced primarily by the PLACENTA. Similar to the pituitary LUTEINIZING HORMONE in structure and function, chorionic gonadotropin is involved in maintaining the CORPUS LUTEUM during pregnancy. CG consists of two noncovalently linked subunits, alpha and beta. Within a species, the alpha subunit is virtually identical to the alpha subunits of the three pituitary glycoprotein hormones (TSH, LH, and FSH), but the beta subunit is unique and confers its biological specificity (CHORIONIC GONADOTROPIN, BETA SUBUNIT, HUMAN).Gonadotropins: Hormones that stimulate gonadal functions such as GAMETOGENESIS and sex steroid hormone production in the OVARY and the TESTIS. Major gonadotropins are glycoproteins produced primarily by the adenohypophysis (GONADOTROPINS, PITUITARY) and the placenta (CHORIONIC GONADOTROPIN). In some species, pituitary PROLACTIN and PLACENTAL LACTOGEN exert some luteotropic activities.Buserelin: A potent synthetic analog of GONADOTROPIN-RELEASING HORMONE with D-serine substitution at residue 6, glycine10 deletion, and other modifications.Fertilization: The fusion of a spermatozoon (SPERMATOZOA) with an OVUM thus resulting in the formation of a ZYGOTE.Follicle Stimulating Hormone: A major gonadotropin secreted by the adenohypophysis (PITUITARY GLAND, ANTERIOR). Follicle-stimulating hormone stimulates GAMETOGENESIS and the supporting cells such as the ovarian GRANULOSA CELLS, the testicular SERTOLI CELLS, and LEYDIG CELLS. FSH consists of two noncovalently linked subunits, alpha and beta. Within a species, the alpha subunit is common in the three pituitary glycoprotein hormones (TSH, LH, and FSH), but the beta subunit is unique and confers its biological specificity.WisconsinAfrican Americans: Persons living in the United States having origins in any of the black groups of Africa.European Continental Ancestry Group: Individuals whose ancestral origins are in the continent of Europe.Reproduction: The total process by which organisms produce offspring. (Stedman, 25th ed)Socioeconomic Factors: Social and economic factors that characterize the individual or group within the social structure.Gonadotropin-Releasing Hormone: A decapeptide that stimulates the synthesis and secretion of both pituitary gonadotropins, LUTEINIZING HORMONE and FOLLICLE STIMULATING HORMONE. GnRH is produced by neurons in the septum PREOPTIC AREA of the HYPOTHALAMUS and released into the pituitary portal blood, leading to stimulation of GONADOTROPHS in the ANTERIOR PITUITARY GLAND.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Oocytes: Female germ cells derived from OOGONIA and termed OOCYTES when they enter MEIOSIS. The primary oocytes begin meiosis but are arrested at the diplotene state until OVULATION at PUBERTY to give rise to haploid secondary oocytes or ova (OVUM).Infertility, Male: The inability of the male to effect FERTILIZATION of an OVUM after a specified period of unprotected intercourse. Male sterility is permanent infertility.Logistic Models: Statistical models which describe the relationship between a qualitative dependent variable (that is, one which can take only certain discrete values, such as the presence or absence of a disease) and an independent variable. A common application is in epidemiology for estimating an individual's risk (probability of a disease) as a function of a given risk factor.Vaginal Birth after Cesarean: Delivery of an infant through the vagina in a female who has had a prior cesarean section.Infant, Small for Gestational Age: An infant having a birth weight lower than expected for its gestational age.Continental Population Groups: Groups of individuals whose putative ancestry is from native continental populations based on similarities in physical appearance.Embryo, Mammalian: The entity of a developing mammal (MAMMALS), generally from the cleavage of a ZYGOTE to the end of embryonic differentiation of basic structures. For the human embryo, this represents the first two months of intrauterine development preceding the stages of the FETUS.Embryonic Development: Morphological and physiological development of EMBRYOS.