Final answer:
The relationship of the fetal parts to one another refers to the fetus's positioning within the uterus. The normal and preferred fetal position for birth is head down. Important aspects of fetal development include placenta function, umbilical cord role, three trimesters of growth, and differences in fetal blood circulation and hemoglobin compared to the postnatal state.
Step-by-step explanation:
The relationship of the fetal parts to one another usually refers to the position that the fetus assumes within the uterus during pregnancy. The most common and ideal positioning for delivery is the cephalic presentation, where the fetus's head is down, facing the mother's back, often referred to as 'head down'. The fetus is usually curled into the 'fetal position', with its back curved, limbs folded, and chin tucked to its chest.
A placenta is made of tissues that provide the exchange of nutrients and gases between the mother and fetus, and it plays a critical role in fetal development by attaching to the uterine wall. The umbilical cord, which connects the fetus to the placenta, comprises two arteries and one vein, facilitating the transportation of oxygenated blood and nutrients to the fetus and the removal of waste products.
In fetal development, critical events occur during the three trimesters, such as organ development, quickening of fetal movements, and preparation for childbirth. The average weight of a full-term infant is approximately 3.4 kg (7.5 lb), while low birth weight (5.5 lb) can be a concern. Fetal viability is the ability of the fetus to survive outside the uterus, which is typically possible after 26 weeks of gestation.
Fetal blood circulation differs from postnatal circulation due to the inactive fetal lungs; oxygen is received through the placenta. Differences also exist between fetal and adult hemoglobin, with fetal hemoglobin having a higher affinity for oxygen to facilitate the transfer from the mother's blood. Any growth restrictions like IUGR can lead to low birth weight, often caused by placental insufficiency, and may impact newborn survival chances.