Babies in-utero do not use their lungs to breathe or their mouths to eat. So how do they get the necessary nutrition and oxygen to grow and thrive? A womb has a complex support system sustaining the fetus with the necessary nutrients and oxygen that are critical to a baby's development while inside the uterus.
Uterus
The uterus is a muscular organ in a female's body that houses the growing infant, placenta, umbilical cord and amniotic sac. When an egg is fertilized it attaches to the uterine wall beginning the pregnancy. The uterus will grow to many times its normal size by the end of the pregnancy. It starts the size of a pear, sitting inside the pelvis. By the 36th week of pregnancy the top of the uterus is under the rib cage.
Placenta
The placenta is a vascular organ that grows onto the wall of the uterus to give a growing fetus everything that it needs. The placenta is responsible for delivering oxygen and nutrients to the baby. It also acts as a trash can. It removes waste products from the baby's blood. In addition, the placenta produces all the hormones necessary to sustain the pregnancy. At delivery, the placenta is about the size of a dinner plate and is expelled after the birth of the baby.
Umbilical Cord
The umbilical cord is the baby's lifeline. It is the super highway that connects the placenta to the baby. It is made up of three blood vessels: two arteries and one vein. The two arteries carry blood away from the fetus to the placenta where it dumps the waste products from the infant into the maternal bloodstream to be filtered out by the kidneys. The vein carries oxygen and nutrient-rich blood from the mother's bloodstream to the infant. All of this happens without the two blood supplies ever mixing.
Amniotic Sac
The amniotic sac contains the baby in a fluid-filled bubble to protect it from the outside world. The sac is sometimes referred to as the membranes. As the baby develops he will start to inhale and exhale the amniotic fluid. This is sometimes called "practice breathing." These movements have nothing to do with getting oxygen, but this exercise helps to develop the lungs.
Complications
There is a danger of the umbilical cord becoming knotted. When this happens the baby's life is at risk. If the knot becomes too tight, the blood supply is cut off from the baby. Without the oxygen-rich blood supply, the baby is starved of oxygen and dies.
MayoClinic.com defines placental abruption as the separation of the placenta from the uterine wall prior to the birth of the baby. The separation can be partial or complete. This is another situation that would inhibit the supply of oxygen to the baby, possibly resulting in stillbirth. Maternal smoking is shown to increase the risk of placental abruption.
