Cats have a placenta, an organ that develops during pregnancy. This temporary structure forms inside the mother’s uterus, establishing a vital connection between her and her developing kittens. It serves as the primary interface for exchanging nutrients, oxygen, and waste products, ensuring the healthy growth of the fetuses throughout gestation. This article explores the feline placenta’s characteristics, functions, and its role during and after birth.
Understanding the Feline Placenta
Cats have a zonary placenta, which forms a belt-like band completely encircling each developing fetus within the uterus. It is also classified as endotheliochorial, indicating close contact between fetal and maternal cells. This structure efficiently transfers substances between the mother and her offspring.
The primary functional unit of the feline placenta is the chorioallantoic membrane (CAM), which develops from the fusion of two fetal membranes: the chorion and the allantois. This membrane forms the main barrier and exchange surface. Microscopically, the placenta consists of a labyrinthine structure where maternal and fetal blood vessels are in close proximity, facilitating exchange without direct mixing of blood.
The placenta is a transient organ, developing only during pregnancy. It continuously grows and remodels to meet the increasing demands of the growing fetuses. Its specialized structure ensures an effective interface for supporting multiple kittens in a litter.
Role of the Placenta in Feline Pregnancy
The placenta performs several functions that maintain pregnancy. It acts as the primary conduit for nutrient supply from the mother to her kittens. Glucose, amino acids, and fatty acids are transported across the placental barrier to fuel fetal growth and development. Oxygen, essential for fetal respiration, is also efficiently delivered through the placenta from the maternal bloodstream.
Beyond nutrient and oxygen delivery, the placenta removes metabolic waste products generated by the developing fetuses. Carbon dioxide and urea, for example, diffuse from the fetal circulation into the maternal blood for excretion. This waste removal process prevents the buildup of harmful substances in the fetal environment. The placenta also provides some mechanical protection to the developing embryos.
The feline placenta is an active endocrine organ, producing various hormones that maintain pregnancy. It synthesizes relaxin, a hormone used as a pregnancy indicator. The placenta also contributes to the production of progesterone and estradiol, which support the uterine environment and help prevent premature labor. It also transfers maternal antibodies to the fetuses, providing passive immunity against certain pathogens before birth.
Post-Birth Events and Care
After each kitten is born, its corresponding placenta is expelled from the uterus. This expulsion is part of the third stage of labor for each kitten. In a normal birthing process, the placenta usually follows the kitten within minutes, though sometimes a few kittens may be born before their placentas are passed. A litter will result in multiple placentas being delivered.
A common behavior in mother cats is placentophagy, the consumption of the expelled placentas. This instinctual behavior has several evolutionary advantages. One reason is to remove any scent that might attract predators to the birthing site and vulnerable newborn kittens. Another theory suggests consuming the placenta provides the mother with nutrients, such as protein and iron, which can aid in her recovery from giving birth and support milk production.
Monitoring the expulsion of placentas is an important aspect of post-birth care. It is advisable to count them to ensure one has been expelled for each kitten born. If a placenta is retained within the uterus, it can lead to serious complications for the mother, including infection (metritis), fever, loss of appetite, lethargy, and decreased milk production. A retained placenta can decompose and cause a dangerous bacterial infection. If there is suspicion of a retained placenta, veterinary attention is necessary to prevent severe health issues.