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).Birth Rate: The number of births in a given population per year or other unit of time.Birth Weight: The mass or quantity of heaviness of an individual at BIRTH. It is expressed by units of pounds or kilograms.Pregnancy: The status during which female mammals carry their developing young (EMBRYOS or FETUSES) in utero before birth, beginning from FERTILIZATION to BIRTH.Infant, Newborn: An infant during the first month after birth.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).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.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.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.Maternal Age: The age of the mother in PREGNANCY.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.Fertilization in Vitro: An assisted reproductive technique that includes the direct handling and manipulation of oocytes and sperm to achieve fertilization in vitro.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.Birth Order: The sequence in which children are born into the family.Reproductive Techniques, Assisted: Clinical and laboratory techniques used to enhance fertility in humans and animals.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.Fetal Death: Death of the developing young in utero. BIRTH of a dead FETUS is STILLBIRTH.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.Congenital Abnormalities: Malformations of organs or body parts during development in utero.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.Infertility: Inability to reproduce after a specified period of unprotected intercourse. Reproductive sterility is permanent infertility.Abortion, Spontaneous: Expulsion of the product of FERTILIZATION before completing the term of GESTATION and without deliberate interference.Stillbirth: The event that a FETUS is born dead or stillborn.Multiple Birth Offspring: The offspring in multiple pregnancies (PREGNANCY, MULTIPLE): TWINS; TRIPLETS; QUADRUPLETS; QUINTUPLETS; etc.Infertility, Female: Diminished or absent ability of a female to achieve conception.Maternal Mortality: Maternal deaths resulting from complications of pregnancy and childbirth in a given population.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.Parity: The number of offspring a female has borne. It is contrasted with GRAVIDITY, which refers to the number of pregnancies, regardless of outcome.Birth Intervals: The lengths of intervals between births to women in the population.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.Ovulation Induction: Techniques for the artifical induction of ovulation, the rupture of the follicle and release of the ovum.Abortion, Habitual: Three or more consecutive spontaneous abortions.Pregnancy, Multiple: The condition of carrying two or more FETUSES simultaneously.Oocyte Retrieval: Procedures to obtain viable OOCYTES from the host. Oocytes most often are collected by needle aspiration from OVARIAN FOLLICLES before OVULATION.Prenatal Care: Care provided the pregnant woman in order to prevent complications, and decrease the incidence of maternal and prenatal mortality.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.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).Birth Injuries: Mechanical or anoxic trauma incurred by the infant during labor or delivery.Perinatal Care: The care of women and a fetus or newborn given before, during, and after delivery from the 28th week of gestation through the 7th day after delivery.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)Abortion, Legal: Termination of pregnancy under conditions allowed under local laws. (POPLINE Thesaurus, 1991)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.Vital Statistics: Used for general articles concerning statistics of births, deaths, marriages, etc.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.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.Sex Ratio: The number of males per 100 females.Perinatal Mortality: Deaths occurring from the 28th week of GESTATION to the 28th day after birth in a given population.Cesarean Section: Extraction of the FETUS by means of abdominal HYSTEROTOMY.Asphyxia Neonatorum: Respiratory failure in the newborn. (Dorland, 27th ed)Embryo Implantation: Endometrial implantation of EMBRYO, MAMMALIAN at the BLASTOCYST stage.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.Home Childbirth: Childbirth taking place in the home.Infant, Small for Gestational Age: An infant having a birth weight lower than expected for its gestational age.Maternal Exposure: Exposure of the female parent, human or animal, to potentially harmful chemical, physical, or biological agents in the environment or to environmental factors that may include ionizing radiation, pathogenic organisms, or toxic chemicals that may affect offspring. It includes pre-conception maternal exposure.Prenatal Diagnosis: Determination of the nature of a pathological condition or disease in the postimplantation EMBRYO; FETUS; or pregnant female before birth.Incidence: The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from PREVALENCE, which refers to all cases, new or old, in the population at a given time.Obstetric Labor Complications: Medical problems associated with OBSTETRIC LABOR, such as BREECH PRESENTATION; PREMATURE OBSTETRIC LABOR; HEMORRHAGE; or others. These complications can affect the well-being of the mother, the FETUS, or both.United StatesFertility Agents, Female: Compounds which increase the capacity to conceive in females.Maternal Health Services: Organized services to provide health care to expectant and nursing mothers.Pregnancy in Adolescence: Pregnancy in human adolescent females under the age of 19.Abnormalities, Drug-Induced: Congenital abnormalities caused by medicinal substances or drugs of abuse given to or taken by the mother, or to which she is inadvertently exposed during the manufacture of such substances. The concept excludes abnormalities resulting from exposure to non-medicinal chemicals in the environment.Vitrification: The transformation of a liquid to a glassy solid i.e., without the formation of crystals during the cooling process.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.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).Infant, Newborn, Diseases: Diseases of newborn infants present at birth (congenital) or developing within the first month of birth. It does not include hereditary diseases not manifesting at birth or within the first 30 days of life nor does it include inborn errors of metabolism. Both HEREDITARY DISEASES and METABOLISM, INBORN ERRORS are available as general concepts.Reproductive Control Agents: Substances used either in the prevention or facilitation of pregnancy.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.Infant, Premature, DiseasesMothers: Female parents, human or animal.Hospitals, Maternity: Special hospitals which provide care to women during pregnancy and parturition.Registries: The systems and processes involved in the establishment, support, management, and operation of registers, e.g., disease registers.Pregnancy Complications, Infectious: The co-occurrence of pregnancy and an INFECTION. The infection may precede or follow FERTILIZATION.Abortion, Eugenic: Abortion performed because of possible fetal defects.Sudden Infant Death: The abrupt and unexplained death of an apparently healthy infant under one year of age, remaining unexplained after a thorough case investigation, including performance of a complete autopsy, examination of the death scene, and review of the clinical history. (Pediatr Pathol 1991 Sep-Oct;11(5):677-84)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.Pregnancy, High-Risk: Pregnancy in which the mother and/or FETUS are at greater than normal risk of MORBIDITY or MORTALITY. Causes include inadequate PRENATAL CARE, previous obstetrical history (ABORTION, SPONTANEOUS), pre-existing maternal disease, pregnancy-induced disease (GESTATIONAL HYPERTENSION), and MULTIPLE PREGNANCY, as well as advanced maternal age above 35.Paternal Age: Age of the biological father.Reproductive History: An important aggregate factor in epidemiological studies of women's health. The concept usually includes the number and timing of pregnancies and their outcomes, the incidence of breast feeding, and may include age of menarche and menopause, regularity of menstruation, fertility, gynecological or obstetric problems, or contraceptive usage.Neonatal Screening: The identification of selected parameters in newborn infants by various tests, examinations, or other procedures. Screening may be performed by clinical or laboratory measures. A screening test is designed to sort out healthy neonates (INFANT, NEWBORN) from those not well, but the screening test is not intended as a diagnostic device, rather instead as epidemiologic.Population Surveillance: Ongoing scrutiny of a population (general population, study population, target population, etc.), generally using methods distinguished by their practicability, uniformity, and frequently their rapidity, rather than by complete accuracy.Prevalence: The total number of cases of a given disease in a specified population at a designated time. It is differentiated from INCIDENCE, which refers to the number of new cases in the population at a given time.Cleft Lip: Congenital defect in the upper lip where the maxillary prominence fails to merge with the merged medial nasal prominences. It is thought to be caused by faulty migration of the mesoderm in the head region.Apgar Score: A method, developed by Dr. Virginia Apgar, to evaluate a newborn's adjustment to extrauterine life. Five items - heart rate, respiratory effort, muscle tone, reflex irritability, and color - are evaluated 60 seconds after birth and again five minutes later on a scale from 0-2, 0 being the lowest, 2 being normal. The five numbers are added for the Apgar score. A score of 0-3 represents severe distress, 4-7 indicates moderate distress, and a score of 7-10 predicts an absence of difficulty in adjusting to extrauterine life.Abortion, Therapeutic: Abortion induced to save the life or health of a pregnant woman. (From Dorland, 28th ed)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.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.Menstruation-Inducing Agents: Chemical compounds that induce menstruation either through direct action on the reproductive organs or through indirect action by relieving another condition of which amenorrhea is a secondary result. (From Dorland, 27th ed)Fertility: The capacity to conceive or to induce conception. It may refer to either the male or female.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.Socioeconomic Factors: Social and economic factors that characterize the individual or group within the social structure.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.Insemination, Artificial, Homologous: Human artificial insemination in which the husband's semen is used.Maternal Welfare: Organized efforts by communities or organizations to improve the health and well-being of the mother.Pregnancy Complications, Cardiovascular: The co-occurrence of pregnancy and a cardiovascular disease. The disease may precede or follow FERTILIZATION and it may or may not have a deleterious effect on the pregnant woman or FETUS.Down Syndrome: A chromosome disorder associated either with an extra chromosome 21 or an effective trisomy for chromosome 21. Clinical manifestations include hypotonia, short stature, brachycephaly, upslanting palpebral fissures, epicanthus, Brushfield spots on the iris, protruding tongue, small ears, short, broad hands, fifth finger clinodactyly, Simian crease, and moderate to severe INTELLECTUAL DISABILITY. Cardiac and gastrointestinal malformations, a marked increase in the incidence of LEUKEMIA, and the early onset of ALZHEIMER DISEASE are also associated with this condition. Pathologic features include the development of NEUROFIBRILLARY TANGLES in neurons and the deposition of AMYLOID BETA-PROTEIN, similar to the pathology of ALZHEIMER DISEASE. (Menkes, Textbook of Child Neurology, 5th ed, p213)Prenatal Exposure Delayed Effects: The consequences of exposing the FETUS in utero to certain factors, such as NUTRITION PHYSIOLOGICAL PHENOMENA; PHYSIOLOGICAL STRESS; DRUGS; RADIATION; and other physical or chemical factors. These consequences are observed later in the offspring after BIRTH.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.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.Infant, Premature: A human infant born before 37 weeks of GESTATION.Labor, Obstetric: The repetitive uterine contraction during childbirth which is associated with the progressive dilation of the uterine cervix (CERVIX UTERI). Successful labor results in the expulsion of the FETUS and PLACENTA. Obstetric labor can be spontaneous or induced (LABOR, INDUCED).Midwifery: The practice of assisting women in childbirth.Maternal Death: The death of the female parent.Odds Ratio: The ratio of two odds. The exposure-odds ratio for case control data is the ratio of the odds in favor of exposure among cases to the odds in favor of exposure among noncases. The disease-odds ratio for a cohort or cross section is the ratio of the odds in favor of disease among the exposed to the odds in favor of disease among the unexposed. The prevalence-odds ratio refers to an odds ratio derived cross-sectionally from studies of prevalent cases.Pregnancy Trimesters: The three approximately equal periods of a normal human PREGNANCY. Each trimester is about three months or 13 to 14 weeks in duration depending on the designation of the first day of gestation.Child Mortality: Number of deaths of children between one year of age to 12 years of age in a given population.Cleft Palate: Congenital fissure of the soft and/or hard palate, due to faulty fusion.Animals, Newborn: Refers to animals in the period of time just after birth.Parturition: The process of giving birth to one or more offspring.Marital Status: A demographic parameter indicating a person's status with respect to marriage, divorce, widowhood, singleness, etc.Fetal Development: Morphological and physiological development of FETUSES.Infant Care: Care of infants in the home or institution.Insemination, Artificial: Artificial introduction of SEMEN or SPERMATOZOA into the VAGINA to facilitate FERTILIZATION.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Vaginal Birth after Cesarean: Delivery of an infant through the vagina in a female who has had a prior cesarean section.EnglandBreast Feeding: The nursing of an infant at the breast.Neural Tube Defects: Congenital malformations of the central nervous system and adjacent structures related to defective neural tube closure during the first trimester of pregnancy generally occurring between days 18-29 of gestation. Ectodermal and mesodermal malformations (mainly involving the skull and vertebrae) may occur as a result of defects of neural tube closure. (From Joynt, Clinical Neurology, 1992, Ch55, pp31-41)Viviparity, Nonmammalian: The capability of bearing live young (rather than eggs) in nonmammalian species. Some species of REPTILES and FISHES exhibit this.Anencephaly: A malformation of the nervous system caused by failure of the anterior neuropore to close. Infants are born with intact spinal cords, cerebellums, and brainstems, but lack formation of neural structures above this level. The skull is only partially formed but the eyes are usually normal. This condition may be associated with folate deficiency. Affected infants are only capable of primitive (brain stem) reflexes and usually do not survive for more than two weeks. (From Menkes, Textbook of Child Neurology, 5th ed, p247)Death Certificates: Official records of individual deaths including the cause of death certified by a physician, and any other required identifying information.Sperm Retrieval: Procedures to obtain viable sperm from the male reproductive tract, including the TESTES, the EPIDIDYMIS, or the VAS DEFERENS.Cause of Death: Factors which produce cessation of all vital bodily functions. They can be analyzed from an epidemiologic viewpoint.Illegitimacy: The state of birth outside of wedlock. It may refer to the offspring or the parents.Pregnancy Trimester, First: The beginning third of a human PREGNANCY, from the first day of the last normal menstrual period (MENSTRUATION) through the completion of 14 weeks (98 days) of gestation.Educational Status: Educational attainment or level of education of individuals.Intensive Care Units, Neonatal: Hospital units providing continuing surveillance and care to acutely ill newborn infants.BrazilAbnormalities, MultipleFetal Diseases: Pathophysiological conditions of the FETUS in the UTERUS. Some fetal diseases may be treated with FETAL THERAPIES.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.Case-Control Studies: Studies which start with the identification of persons with a disease of interest and a control (comparison, referent) group without the disease. The relationship of an attribute to the disease is examined by comparing diseased and non-diseased persons with regard to the frequency or levels of the attribute in each group.Perinatology: The branch of medicine dealing with the fetus and infant during the perinatal period. The perinatal period begins with the twenty-eighth week of gestation and ends twenty-eight days after birth. (From Dorland, 27th ed)Postpartum Hemorrhage: Excess blood loss from uterine bleeding associated with OBSTETRIC LABOR or CHILDBIRTH. It is defined as blood loss greater than 500 ml or of the amount that adversely affects the maternal physiology, such as BLOOD PRESSURE and HEMATOCRIT. Postpartum hemorrhage is divided into two categories, immediate (within first 24 hours after birth) or delayed (after 24 hours postpartum).Incubators: Insulated enclosures in which temperature, humidity, and other environmental conditions can be regulated at levels optimal for growth, hatching, reproduction, or metabolic reactions.Fertility Agents: Drugs used to increase fertility or to treat infertility.European Continental Ancestry Group: Individuals whose ancestral origins are in the continent of Europe.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.Intensive Care, Neonatal: Continuous care and monitoring of newborn infants with life-threatening conditions, in any setting.Gravidity: The number of pregnancies, complete or incomplete, experienced by a female. It is different from PARITY, which is the number of offspring borne. (From Stedman, 26th ed)Child Development: The continuous sequential physiological and psychological maturing of an individual from birth up to but not including ADOLESCENCE.Triplets: Three individuals derived from three FETUSES that were fertilized at or about the same time, developed in the UTERUS simultaneously, and born to the same mother.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.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.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.Heart Defects, Congenital: Developmental abnormalities involving structures of the heart. These defects are present at birth but may be discovered later in life.Obstetrics and Gynecology Department, Hospital: Hospital department responsible for the administration and management of services provided for obstetric and gynecologic patients.Medical Record Linkage: The creation and maintenance of medical and vital records in multiple institutions in a manner that will facilitate the combined use of the records of identified individuals.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.Pregnancy, Twin: The condition of carrying TWINS simultaneously.Ultrasonography, Prenatal: The visualization of tissues during pregnancy through recording of the echoes of ultrasonic waves directed into the body. The procedure may be applied with reference to the mother or the fetus and with reference to organs or the detection of maternal or fetal disease.Body Height: The distance from the sole to the crown of the head with body standing on a flat surface and fully extended.Postnatal Care: The care provided to women and their NEWBORNS for the first few months following CHILDBIRTH.DenmarkProbability: The study of chance processes or the relative frequency characterizing a chance process.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).Hernia, Umbilical: A HERNIA due to an imperfect closure or weakness of the umbilical ring. It appears as a skin-covered protrusion at the UMBILICUS during crying, coughing, or straining. The hernia generally consists of OMENTUM or SMALL INTESTINE. The vast majority of umbilical hernias are congenital but can be acquired due to severe abdominal distention.Infant Welfare: Organized efforts by communities or organizations to improve the health and well-being of infants.Infectious Disease Transmission, Vertical: The transmission of infectious disease or pathogens from one generation to another. It includes transmission in utero or intrapartum by exposure to blood and secretions, and postpartum exposure via breastfeeding.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).Risk: The probability that an event will occur. It encompasses a variety of measures of the probability of a generally unfavorable outcome.Pregnancy Complications, Neoplastic: The co-occurrence of pregnancy and NEOPLASMS. The neoplastic disease may precede or follow FERTILIZATION.Paternal Exposure: Exposure of the male parent, human or animal, to potentially harmful chemical, physical, or biological agents in the environment or to environmental factors that may include ionizing radiation, pathogenic organisms, or toxic chemicals that may affect offspring.Preconception Care: An organized and comprehensive program of health care that identifies and reduces a woman's reproductive risks before conception through risk assessment, health promotion, and interventions. Preconception care programs may be designed to include the male partner in providing counseling and educational information in preparation for fatherhood, such as genetic counseling and testing, financial and family planning, etc. This concept is different from PRENATAL CARE, which occurs during pregnancy.Regression Analysis: Procedures for finding the mathematical function which best describes the relationship between a dependent variable and one or more independent variables. In linear regression (see LINEAR MODELS) the relationship is constrained to be a straight line and LEAST-SQUARES ANALYSIS is used to determine the best fit. In logistic regression (see LOGISTIC MODELS) the dependent variable is qualitative rather than continuously variable and LIKELIHOOD FUNCTIONS are used to find the best relationship. In multiple regression, the dependent variable is considered to depend on more than a single independent variable.Developing Countries: Countries in the process of change with economic growth, that is, an increase in production, per capita consumption, and income. The process of economic growth involves better utilization of natural and human resources, which results in a change in the social, political, and economic structures.Fertilization: The fusion of a spermatozoon (SPERMATOZOA) with an OVUM thus resulting in the formation of a ZYGOTE.Anti-Mullerian Hormone: A glycoprotein that causes regression of MULLERIAN DUCTS. It is produced by SERTOLI CELLS of the TESTES. In the absence of this hormone, the Mullerian ducts develop into structures of the female reproductive tract. In males, defects of this hormone result in persistent Mullerian duct, a form of MALE PSEUDOHERMAPHRODITISM.Follow-Up Studies: Studies in which individuals or populations are followed to assess the outcome of exposures, procedures, or effects of a characteristic, e.g., occurrence of disease.Great BritainRisk Assessment: The qualitative or quantitative estimation of the likelihood of adverse effects that may result from exposure to specified health hazards or from the absence of beneficial influences. (Last, Dictionary of Epidemiology, 1988)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.WalesNepalMaternal-Fetal Exchange: Exchange of substances between the maternal blood and the fetal blood at the PLACENTA via PLACENTAL CIRCULATION. The placental barrier excludes microbial or viral transmission.CaliforniaDemography: Statistical interpretation and description of a population with reference to distribution, composition, or structure.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)Polycystic Ovary Syndrome: A complex disorder characterized by infertility, HIRSUTISM; OBESITY; and various menstrual disturbances such as OLIGOMENORRHEA; AMENORRHEA; ANOVULATION. Polycystic ovary syndrome is usually associated with bilateral enlarged ovaries studded with atretic follicles, not with cysts. The term, polycystic ovary, is misleading.Fetal Monitoring: Physiologic or biochemical monitoring of the fetus. It is usually done during LABOR, OBSTETRIC and may be performed in conjunction with the monitoring of uterine activity. It may also be performed prenatally as when the mother is undergoing surgery.Reproduction: The total process by which organisms produce offspring. (Stedman, 25th ed)Rural Population: The inhabitants of rural areas or of small towns classified as rural.Fetus: The unborn young of a viviparous mammal, in the postembryonic period, after the major structures have been outlined. In humans, the unborn young from the end of the eighth week after CONCEPTION until BIRTH, as distinguished from the earlier EMBRYO, MAMMALIAN.Pregnant Women: Human females who are pregnant, as cultural, psychological, or sociological entities.Insemination, Artificial, Heterologous: Human artificial insemination in which the semen used is that of a man other than the woman's husband.Marriage: The social institution involving legal and/or religious sanction whereby individuals are joined together.Pregnancy, Unwanted: Pregnancy, usually accidental, that is not desired by the parent or parents.Salpingostomy: Formation of an artificial opening in a fallopian tube.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.African Americans: Persons living in the United States having origins in any of the black groups of Africa.Data Collection: Systematic gathering of data for a particular purpose from various sources, including questionnaires, interviews, observation, existing records, and electronic devices. The process is usually preliminary to statistical analysis of the data.Western Australia: A state in western Australia. Its capital is Perth. It was first visited by the Dutch in 1616 but the English took possession in 1791 and permanent colonization began in 1829. It was a penal settlement 1850-1888, became part of the colonial government in 1886, and was granted self government in 1890. (From Webster's New Geographical Dictionary, 1988, p1329)Syphilis, Congenital: Syphilis acquired in utero and manifested by any of several characteristic tooth (Hutchinson's teeth) or bone malformations and by active mucocutaneous syphilis at birth or shortly thereafter. Ocular and neurologic changes may also occur.Obstetrical Forceps: Surgical instrument designed to extract the newborn by the head from the maternal passages without injury to it or the mother.Canada: The largest country in North America, comprising 10 provinces and three territories. Its capital is Ottawa.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.Social Class: A stratum of people with similar position and prestige; includes social stratification. Social class is measured by criteria such as education, occupation, and income.Hypertension, Pregnancy-Induced: A condition in pregnant women with elevated systolic (>140 mm Hg) and diastolic (>90 mm Hg) blood pressure on at least two occasions 6 h apart. HYPERTENSION complicates 8-10% of all pregnancies, generally after 20 weeks of gestation. Gestational hypertension can be divided into several broad categories according to the complexity and associated symptoms, such as EDEMA; PROTEINURIA; SEIZURES; abnormalities in BLOOD COAGULATION and liver functions.Obstetrics: A medical-surgical specialty concerned with management and care of women during pregnancy, parturition, and the puerperium.Ethnic Groups: A group of people with a common cultural heritage that sets them apart from others in a variety of social relationships.