fetus

Examples of fetus in the following topics:

• Fetal Circulation

  • The fetus obtains oxygen and nutrients from the mother through the placenta and the umbilical cord.
  • The core concept behind fetal circulation is that fetal hemoglobin has a higher affinity for oxygen than adult hemoglobin, which allows a diffusion of oxygen from the mother's circulatory system to the fetus.
  • The circulatory system of the mother is not directly connected to that of the fetus, so the placenta functions as the respiratory center for the fetus as well as a site of filtration for plasma nutrients and wastes.
  • Blood from the placenta is carried to the fetus by the umbilical vein.
  • In the fetus, there is a special connection between the pulmonary artery and the aorta, called the ductus arteriosus, which directs most of this blood away from the lungs (which aren't being used for respiration at this point as the fetus is suspended in amniotic fluid).

• Amnion Development

  • The amnion contains the fluid that cushions and protects the fetus.
  • The amniotic fluid allows the free movements of the fetus during the later stages of pregnancy and also protects it by diminishing the risk of injury.
  • Note: That some of the liquor amnii is swallowed by the fetus is proved by the fact that epidermal debris and hairs have been found among the contents of the fetal alimentary canal.

• Introduction to Pregnancy and Human Development

  • The prenatal offspring or conceptus is referred to as an embryo or fetus.
  • After that, the term fetus is used.
  • The first trimester carries the highest risk of miscarriage (natural death of embryo or fetus).
  • During the second trimester, the development of the fetus can be more easily monitored.
  • Ultrasound is used to monitor the age and health of the fetus during pregnancy.

• Placenta

  • The placenta is an organ that connects the developing fetus to the uterine to the mother's blood supply.
  • Nutrient transfer to the fetus occurs via both active and passive transport.
  • IgG antibodies can pass through the human placenta, thereby providing protection to the fetus in utero.
  • The placenta functions as a selective maternal-fetal barrier against transmission of microbes to the fetus.
  • It also regulates maternal glucose, protein, and fat levels so that this is always available to the fetus.

• Fetal Development

  • The head makes up nearly half of the fetus' size.
  • Week 18: The fetus starts to hear and is startled by noise.
  • Week 23: The fetus weighs over a pound.
  • Weeks 24: The fetus is almost a foot long.
  • The fetus is considered full-term between weeks 37 and 40, which means that the fetus is considered sufficiently developed for life outside the uterus.

• Prenatal Diagnostic Tests

  • Prenatal diagnosis is a way to screen a fetus for diseases and/or conditions that may increase morbidity and/or mortality.
  • Prenatal diagnosis and prenatal screening are methods for testing for diseases or conditions in a fetus or embryo before it is born.
  • Chorionic villus sampling is associated with slightly more risky to the fetus.
  • The results of the blood tests are then combined with the NT ultrasound measurements, maternal age, and gestational age of the fetus to yield a risk score for Down Syndrome, Trisomy 18, and Trisomy 13.
  • This karyotype indicates that the fetus has Down Syndrome as it has three of chromosome 21 instead of two.

• Anatomical Changes

  • During pregnancy, women undergo many physical changes due to hormonal fluctuations and the need to accommodate a growing fetus.
  • The umbilical cord connects the embryo or fetus to the placenta.
  • Although the fetus begins to move and takes a recognizable human shape during the first trimester, it is not until the second trimester that movement of the fetus, often referred to as "quickening", can be felt by the woman.
  • The fetus will be growing the most rapidly during this stage, gaining up to 28g per day.
  • Poor posture occurs naturally from the stretching of the woman's abdominal muscles as the fetus grows.

• Teratogens

  • A teratogen is a compound which permanently deforms the function or structure of a developing embryo or fetus.
  • A teratogen is a compound which permanently deforms the function or structure of a developing embryo or fetus in utero.

• Erythroblastosis Fetalis (Hemolytic Disease of the Newborn)

  • Also known as erythroblastosis fetalis, this an alloimmune condition that develops in a fetus when the IgG molecules (one of the five main types of antibodies) produced by the mother pass through the placenta.
  • The red cells are broken down and the fetus can develop reticulocytosis and anemia.
  • If a mother is exposed to a foreign antigen and produces the antibody type IgG (as opposed to IgM which does not cross the placenta), the IgG will target the antigen, if present in the fetus, and may affect it in-utero and persist after delivery.
  • In subsequent pregnancies, if there is a similar incompatibility in the fetus, these antibodies are then able to cross the placenta into the fetal bloodstream to attach to the red blood cells and cause hemolysis.
  • In other words, if a mother has anti-RhD (D being the major Rhesus antigen) IgG antibodies as a result of previously carrying a RhD-positive fetus, this antibody will only affect a fetus with RhD-positive blood.

• Dystocia and Cesarean Section

  • A prolonged second stage of labor is another type of dystocia whereby the fetus has not been delivered within three hours in a nulliparous woman, or two hours in multiparous woman, after her cervix has become fully dilated.
  • A cesarean section is a surgical procedure in which one or more incisions are made through a mother's abdomen (laparotomy) and uterus (hysterotomy) to deliver one or more babies; or, rarely, to remove a dead fetus.
  • A Cesarean section is generally performed when the life of the mother or fetus is at risk by continuing a natural delivery.