Fetal Weight: The weight of the FETUS in utero. It is usually estimated by various formulas based on measurements made during PRENATAL ULTRASONOGRAPHY.Fetal Development: Morphological and physiological development of FETUSES.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 Weight: The mass or quantity of heaviness of an individual. It is expressed by units of pounds or kilograms.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.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.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.Fetal Growth Retardation: The failure of a FETUS to attain its expected FETAL GROWTH at any GESTATIONAL AGE.Placenta: A highly vascularized mammalian fetal-maternal organ and major site of transport of oxygen, nutrients, and fetal waste products. It includes a fetal portion (CHORIONIC VILLI) derived from TROPHOBLASTS and a maternal portion (DECIDUA) derived from the uterine ENDOMETRIUM. The placenta produces an array of steroid, protein and peptide hormones (PLACENTAL HORMONES).Pregnancy Trimester, Third: The last third of a human PREGNANCY, from the beginning of the 29th through the 42nd completed week (197 to 294 days) of gestation.Fetal Macrosomia: A condition of fetal overgrowth leading to a large-for-gestational-age FETUS. It is defined as BIRTH WEIGHT greater than 4,000 grams or above the 90th percentile for population and sex-specific growth curves. It is commonly seen in GESTATIONAL DIABETES; PROLONGED PREGNANCY; and pregnancies complicated by pre-existing diabetes mellitus.Weight Gain: Increase in BODY WEIGHT over existing weight.Biometry: The use of statistical and mathematical methods to analyze biological observations and phenomena.Embryonic and Fetal Development: Morphological and physiological development of EMBRYOS or FETUSES.Weight Loss: Decrease in existing BODY WEIGHT.Litter Size: The number of offspring produced at one birth by a viviparous animal.Pregnancy, Animal: The process of bearing developing young (EMBRYOS or FETUSES) in utero in non-human mammals, beginning from FERTILIZATION to BIRTH.Organ Size: The measurement of an organ in volume, mass, or heaviness.Infant, Newborn: An infant during the first month after birth.Molecular Weight: The sum of the weight of all the atoms in a molecule.Umbilical Arteries: Specialized arterial vessels in the umbilical cord. They carry waste and deoxygenated blood from the FETUS to the mother via the PLACENTA. In humans, there are usually two umbilical arteries but sometimes one.Anthropometry: The technique that deals with the measurement of the size, weight, and proportions of the human or other primate body.Maternal-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.Fetal Nutrition Disorders: Disorders caused by nutritional imbalance, either overnutrition or undernutrition, in the FETUS in utero.Amniotic Fluid: A clear, yellowish liquid that envelopes the FETUS inside the sac of AMNION. In the first trimester, it is likely a transudate of maternal or fetal plasma. In the second trimester, amniotic fluid derives primarily from fetal lung and kidney. Cells or substances in this fluid can be removed for prenatal diagnostic tests (AMNIOCENTESIS).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.Pregnancy Trimester, Second: The middle third of a human PREGNANCY, from the beginning of the 15th through the 28th completed week (99 to 196 days) of gestation.Fetal Resorption: The disintegration and assimilation of the dead FETUS in the UTERUS at any stage after the completion of organogenesis which, in humans, is after the 9th week of GESTATION. It does not include embryo resorption (see EMBRYO LOSS).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.Uterus: The hollow thick-walled muscular organ in the female PELVIS. It consists of the fundus (the body) which is the site of EMBRYO IMPLANTATION and FETAL DEVELOPMENT. Beyond the isthmus at the perineal end of fundus, is CERVIX UTERI (the neck) opening into VAGINA. Beyond the isthmi at the upper abdominal end of fundus, are the FALLOPIAN TUBES.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.Pregnancy, Twin: The condition of carrying TWINS simultaneously.Placental Circulation: The circulation of BLOOD, of both the mother and the FETUS, through the PLACENTA.Oligohydramnios: A condition of abnormally low AMNIOTIC FLUID volume. Principal causes include malformations of fetal URINARY TRACT; FETAL GROWTH RETARDATION; GESTATIONAL HYPERTENSION; nicotine poisoning; and PROLONGED PREGNANCY.Reproducibility of Results: The statistical reproducibility of measurements (often in a clinical context), including the testing of instrumentation or techniques to obtain reproducible results. The concept includes reproducibility of physiological measurements, which may be used to develop rules to assess probability or prognosis, or response to a stimulus; reproducibility of occurrence of a condition; and reproducibility of experimental results.Abdomen: That portion of the body that lies between the THORAX and the PELVIS.Fetal Viability: The potential of the FETUS to survive outside the UTERUS after birth, natural or induced. Fetal viability depends largely on the FETAL ORGAN MATURITY, and environmental conditions.Crown-Rump Length: In utero measurement corresponding to the sitting height (crown to rump) of the fetus. Length is considered a more accurate criterion of the age of the fetus than is the weight. The average crown-rump length of the fetus at term is 36 cm. (From Williams Obstetrics, 18th ed, p91)Parietal Bone: One of a pair of irregularly shaped quadrilateral bones situated between the FRONTAL BONE and OCCIPITAL BONE, which together form the sides of the CRANIUM.Predictive Value of Tests: In screening and diagnostic tests, the probability that a person with a positive test is a true positive (i.e., has the disease), is referred to as the predictive value of a positive test; whereas, the predictive value of a negative test is the probability that the person with a negative test does not have the disease. Predictive value is related to the sensitivity and specificity of the test.Teratogens: An agent that causes the production of physical defects in the developing embryo.Pregnancy, Prolonged: A term used to describe pregnancies that exceed the upper limit of a normal gestational period. In humans, a prolonged pregnancy is defined as one that extends beyond 42 weeks (294 days) after the first day of the last menstrual period (MENSTRUATION), or birth with gestational age of 41 weeks or more.Pregnancy in Diabetics: The state of PREGNANCY in women with DIABETES MELLITUS. This does not include either symptomatic diabetes or GLUCOSE INTOLERANCE induced by pregnancy (DIABETES, GESTATIONAL) which resolves at the end of pregnancy.Sheep: Any of the ruminant mammals with curved horns in the genus Ovis, family Bovidae. They possess lachrymal grooves and interdigital glands, which are absent in GOATS.Polyhydramnios: A condition of abnormally high AMNIOTIC FLUID volume, such as greater than 2,000 ml in the LAST TRIMESTER and usually diagnosed by ultrasonographic criteria (AMNIOTIC FLUID INDEX). It is associated with maternal DIABETES MELLITUS; MULTIPLE PREGNANCY; CHROMOSOMAL DISORDERS; and congenital abnormalities.Infant, Small for Gestational Age: An infant having a birth weight lower than expected for its gestational age.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.Parity: The number of offspring a female has borne. It is contrasted with GRAVIDITY, which refers to the number of pregnancies, regardless of outcome.Thigh: The portion of the leg in humans and other animals found between the HIP and KNEE.Ultrasonography: The visualization of deep structures of the body by recording the reflections or echoes of ultrasonic pulses directed into the tissues. Use of ultrasound for imaging or diagnostic purposes employs frequencies ranging from 1.6 to 10 megahertz.Reference Values: The range or frequency distribution of a measurement in a population (of organisms, organs or things) that has not been selected for the presence of disease or abnormality.Placental Insufficiency: Failure of the PLACENTA to deliver an adequate supply of nutrients and OXYGEN to the FETUS.Fetal Death: Death of the developing young in utero. BIRTH of a dead FETUS is STILLBIRTH.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.Fetal Blood: Blood of the fetus. Exchange of nutrients and waste between the fetal and maternal blood occurs via the PLACENTA. The cord blood is blood contained in the umbilical vessels (UMBILICAL CORD) at the time of delivery.Fetal Heart: The heart of the fetus of any viviparous animal. It refers to the heart in the postembryonic period and is differentiated from the embryonic heart (HEART/embryology) only on the basis of time.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).Sensitivity and Specificity: Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Specificity is the probability of correctly determining the absence of a condition. (From Last, Dictionary of Epidemiology, 2d ed)Femur: The longest and largest bone of the skeleton, it is situated between the hip and the knee.Maternal Nutritional Physiological Phenomena: Nutrition of a mother which affects the health of the FETUS and INFANT as well as herself.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.Swine: Any of various animals that constitute the family Suidae and comprise stout-bodied, short-legged omnivorous mammals with thick skin, usually covered with coarse bristles, a rather long mobile snout, and small tail. Included are the genera Babyrousa, Phacochoerus (wart hogs), and Sus, the latter containing the domestic pig (see SUS SCROFA).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.