Vaginal Birth after Cesarean: Delivery of an infant through the vagina in a female who has had a prior cesarean section.Trial of Labor: Allowing a woman to be in LABOR, OBSTETRIC long enough to determine if vaginal birth may be anticipated.Uterine Rupture: A complete separation or tear in the wall of the UTERUS with or without expulsion of the FETUS. It may be due to injuries, multiple pregnancies, large fetus, previous scarring, or obstruction.Cesarean Section, Repeat: Extraction of the fetus by abdominal hysterotomy anytime following a previous cesarean.Episiotomy: An incision of the posterior vaginal wall and a portion of the pudenda which enlarges the vaginal introitus to facilitate delivery and prevent lacerations.Cesarean Section: Extraction of the FETUS by means of abdominal HYSTEROTOMY.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.Extraction, Obstetrical: Extraction of the fetus by means of obstetrical instruments.Parturition: The process of giving birth to one or more offspring.Perineum: The body region lying between the genital area and the ANUS on the surface of the trunk, and to the shallow compartment lying deep to this area that is inferior to the PELVIC DIAPHRAGM. The surface area is between the VULVA and the anus in the female, and between the SCROTUM and the anus in the male.Pregnancy: The status during which female mammals carry their developing young (EMBRYOS or FETUSES) in utero before birth, beginning from FERTILIZATION to BIRTH.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.Lacerations: Torn, ragged, mangled wounds.Labor Stage, Third: The final period of OBSTETRIC LABOR that is from the expulsion of the FETUS to the expulsion of the PLACENTA.Cephalopelvic Disproportion: A condition in which the HEAD of the FETUS is larger than the mother's PELVIS through which the fetal head must pass during a vaginal delivery.Oxytocics: Drugs that stimulate contraction of the myometrium. They are used to induce LABOR, OBSTETRIC at term, to prevent or control postpartum or postabortion hemorrhage, and to assess fetal status in high risk pregnancies. They may also be used alone or with other drugs to induce abortions (ABORTIFACIENTS). Oxytocics used clinically include the neurohypophyseal hormone OXYTOCIN and certain prostaglandins and ergot alkaloids. (From AMA Drug Evaluations, 1994, p1157)Obstetrical Forceps: Surgical instrument designed to extract the newborn by the head from the maternal passages without injury to it or the mother.Birth Weight: The mass or quantity of heaviness of an individual at BIRTH. It is expressed by units of pounds or kilograms.Labor, Induced: Artificially induced UTERINE CONTRACTION. Generally, LABOR, OBSTETRIC is induced with the intent to cause delivery of the fetus and termination of pregnancy.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).Birth Rate: The number of births in a given population per year or other unit of time.Labor Stage, Second: The period of OBSTETRIC LABOR that is from the complete dilatation of the CERVIX UTERI to the expulsion of the FETUS.Breech Presentation: A malpresentation of the FETUS at near term or during OBSTETRIC LABOR with the fetal cephalic pole in the fundus of the UTERUS. There are three types of breech: the complete breech with flexed hips and knees; the incomplete breech with one or both hips partially or fully extended; the frank breech with flexed hips and extended knees.Parity: The number of offspring a female has borne. It is contrasted with GRAVIDITY, which refers to the number of pregnancies, regardless of outcome.Pelvic Floor: Soft tissue formed mainly by the pelvic diaphragm, which is composed of the two levator ani and two coccygeus muscles. The pelvic diaphragm lies just below the pelvic aperture (outlet) and separates the pelvic cavity from the PERINEUM. It extends between the PUBIC BONE anteriorly and the COCCYX posteriorly.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.Infant, Newborn: An infant during the first month after birth.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).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).Pelvic Organ Prolapse: Abnormal descent of a pelvic organ resulting in the protrusion of the organ beyond its normal anatomical confines. Symptoms often include vaginal discomfort, DYSPAREUNIA; URINARY STRESS INCONTINENCE; and FECAL INCONTINENCE.Obstetrics: A medical-surgical specialty concerned with management and care of women during pregnancy, parturition, and the puerperium.Prenatal Care: Care provided the pregnant woman in order to prevent complications, and decrease the incidence of maternal and prenatal mortality.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.Postpartum Period: In females, the period that is shortly after giving birth (PARTURITION).Urinary Incontinence, Stress: Involuntary discharge of URINE as a result of physical activities that increase abdominal pressure on the URINARY BLADDER without detrusor contraction or overdistended bladder. The subtypes are classified by the degree of leakage, descent and opening of the bladder neck and URETHRA without bladder contraction, and sphincter deficiency.Surgical Procedures, Elective: Surgery which could be postponed or not done at all without danger to the patient. Elective surgery includes procedures to correct non-life-threatening medical problems as well as to alleviate conditions causing psychological stress or other potential risk to patients, e.g., cosmetic or contraceptive surgery.Birth Order: The sequence in which children are born into the family.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.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.United StatesRetrospective 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.Research Support, U.S. Gov't, Non-P.H.S.Research Support, U.S. Gov't, P.H.S.Research Support, Non-U.S. Gov'tResearch Support, U.S. GovernmentAbbreviations as Topic: Shortened forms of written words or phrases used for brevity.Libraries, Digital: Libraries in which a major proportion of the resources are available in machine-readable format, rather than on paper or MICROFORM.Textbooks as Topic: Books used in the study of a subject that contain a systematic presentation of the principles and vocabulary of a subject.United States Agency for Healthcare Research and Quality: An agency of the PUBLIC HEALTH SERVICE established in 1990 to "provide indexing, abstracting, translating, publishing, and other services leading to a more effective and timely dissemination of information on research, demonstration projects, and evaluations with respect to health care to public and private entities and individuals engaged in the improvement of health care delivery..." It supersedes the National Center for Health Services Research. The United States Agency for Health Care Policy and Research was renamed Agency for Healthcare Research and Quality (AHRQ) under the Healthcare Research and Quality Act of 1999.National Library of Medicine (U.S.): An agency of the NATIONAL INSTITUTES OF HEALTH concerned with overall planning, promoting, and administering programs pertaining to advancement of medical and related sciences. Major activities of this institute include the collection, dissemination, and exchange of information important to the progress of medicine and health, research in medical informatics and support for medical library development.National Institute of Child Health and Human Development (U.S.): Component of the NATIONAL INSTITUTES OF HEALTH. It was initially established to investigate the broad aspects of human development as a means of understanding developmental disabilities, including mental retardation, and the events that occur during pregnancy. It now conducts and supports research on all stages of human development. It was established in 1962.