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1. Introduction The placenta is a unique, temporary, but vital organ that develops during pregnancy in mammals, including humans. It forms a physical and functional connection between the mother and the developing fetus. Pregnancy involves several temporary structures, such as the placenta, amniotic fluid, and umbilical cord, which are essential for fetal survival, growth, and development inside the uterus. 2. Definition of Placenta The placenta is a vascular organ that connects the fetus to the uterine wall. Origin: It originates from the trophoblastic layer of the fertilized ovum, which forms the chorionic villi. Development: The chorionic villi become more profuse in the decidua basalis (the part of the endometrium beneath the implanted embryo), forming the Chorionic Frondosum, which develops into the placenta. The villi under the capsular decidua degenerate and form the chorionic leave, which is the origin of the chorionic membrane. The placenta is completely formed and functioning from 10-12 weeks after fertilization. 3. Structure and Anatomy of Placenta Gross Anatomy at Term: Shape: A round, flat circular disc. Dimensions: Approximately 15-20 cm in diameter and 2.5 cm thick at the center, thinning off towards the edge. Weight: About 500 gm (or 1/6th of the baby's weight at birth). Texture: Feels spongy. Surfaces: Fetal Surface: Covered by smooth, glistening, and shiny amnion. The umbilical cord is typically attached at or near its center, with fetal blood vessels visible spreading out to the edge. Maternal Surface: Rough, spongy, and dark (dull) red in color due to maternal blood. It is mapped out into 15-20 lobes or cotyledons separated by sulci. Small grayish spots may be visible due to calcium deposition in degenerated areas. 4. Function of Placenta Respiratory: Acts as a fetal lung. The fetus absorbs oxygen from maternal hemoglobin via simple osmosis and diffusion and gives off carbon dioxide (CO_2) into maternal circulation. Nutritive: Supplies adequate nutrition; it changes complex foods into simpler compounds easier for the fetus to absorb. It transfers amino acids, glucose (stored as glycogen), fatty acids, vitamins, minerals, water, and electrolytes. Excretory: Acts as a fetal kidney, filtering blood to eliminate waste products like urea and CO_2 from the fetus into maternal circulation. Endocrine (Hormone Secretion): HCG (Human Chorionic Gonadotrophin): Produced by cytotrophoblasts from the earliest days; stimulates the corpus luteum to produce progesterone and estrogen. It peaks at 60-80 days and is the basis for pregnancy tests. Progesterone: Produced by the syncytial layer from the 3rd month; relaxes smooth muscles and reduces uterine excitability. Estrogen: Produced from the 6th week; levels rise until term to initiate lactation. HPL (Human Placenta Lactogen): Has metabolic effects on carbohydrates and lipids. Storage: Stores glucose (as glycogen), iron, and vitamins (A & D). Protection: The placental membrane has a limited barrier function. It transfers IgG antibodies to the infant, providing immunity for the first 3 months of life. Haemopoietic: It forms fetal hemoglobin. 5. Abnormalities of Placenta Abnormal Shape: Circumvallate Placenta: Central chorionic plate surrounded by a thick whitish ring of double-folded chorion and amnion. Associated with antepartum hemorrhage or preterm labor. Succenturiate (Accessory) Placenta: An accessory lobe attached to the membranes with blood vessels running to it. If retained, it leads to PPH or infection. Bipartite or Tripartite Placenta: The placenta is divided into two or three separate segments, and the cord joins them shortly after leaving the placenta. Retention of one lobe causes PPH or puerperal infection. Placenta Fenestrata: A rare anomaly where a hole or "window" appears in the center of the placenta. It may be wrongly taken for a missing lobe. Abnormal Size/Weight: Large/Heavy Placenta: Size and weight are increased in cases of congenital syphilis, hydrops foetalis, and maternal DM. Small Placenta: Linked to placental insufficiency, hypertension, or chromosomal abnormalities. Abnormal Position: Placenta Praevia: Attached partly or completely to the lower uterine segment. Abnormal Adhesion (PAS): Placenta Accreta: Villi attach deeply/directly to the myometrium. Placenta Increta: Villi invade into the myometrium. Placenta Percreta: Villi penetrate through the entire myometrium to the serosa or nearby organs (e.g., bladder). 6. Definition of Amniotic Fluid A clear, pale straw-colored or slightly yellowish liquid that surrounds the fetus inside the amniotic sac. Volume: Normally 500–1,500 ml. Oligohydramnios: < 500 ml. Polyhydramnios: > 1,500 ml. Composition: 99% water and 1% solids (lanugo, vernix caseosa, epithelia cells, protein, and electrolytes like sodium and calcium). It has a pH of 7.0–7.5. 7. Function of Amniotic Fluid Protection: Acts as a cushion against external trauma and pressure. Temperature Regulation: Maintains a stable environment. Growth/Movement: Allows free movement for muscle and bone development. Lung Maturation: Inhalation/exhalation of fluid promotes lung growth. Prevents Adhesions: Stops fetal parts from sticking to the amnion. Labor Aid: Aids effacement and dilatation of the cervix and equalizes pressure during contractions. 8. Umbilical Cord Definition: The structure and lifeline connecting the fetus to the placenta. Structure: Composed of a jelly-like material called Wharton’s jelly, containing one large umbilical vein (oxygenated blood) and two arteries (deoxygenated blood). Length: Approximately 50 cm. Development: Forms during the 5th week of gestation. 9. Abnormalities of Umbilical Cord A) Abnormal Cord Insertion 1. Battledore insertion (Marginal insertion): Umbilical cord is attached to the edge of the placenta Gives squash-racket appearance Usually minimal clinical significance 2. Velamentous insertion: Cord inserted into the membranes away from the placenta Umbilical vessels run through membranes (vasa praevia) Vessels may cross cervix → fetal distress Vessels lack Wharton’s jelly → risk of compression B) Abnormal Cord Length 1. Short cord: Intrapartum haemorrhage Delayed descent of the foetus Inversion of the uterus Normal cord length: 50–60 cm 2. Long cord: Cord presentation and prolapse Coiling around the neck True knots of the cord C) Knots of the Cord 1. True knot: Foetus passes through a loop of the cord Tightening may cause foetal asphyxia 2. False knot: Localised collection of Wharton’s jelly No clinical significance.