CH 21 OB/GYN

Composition: The umbilical cord consists of two arteries and one vein. It is surrounded by Wharton's jelly and enclosed in a layer of the amnion.
Structure: The umbilical arteries are longer than the umbilical vein and are twisted around the vein, which gives the cord a "braided" appearance.
Function: The cord facilitates the transport of blood between the fetus and the fetal portion of the placenta.
Insertion: The insertion point of the umbilical cord is typically central.

The umbilical cord forms during the first 5 weeks of gestation.
It is lined with epithelium that forms from the amniotic membrane enveloping it.
Gut Herniation: Between 7 and 10 weeks, the gut herniates into the proximal cord but returns by 10 to 12 weeks.
If the abdominal wall insertion of the cord appears normal, it rules out defects.

Components: The umbilical cord contains two arteries and one vein.
Development Timeline: The formation begins in the first 5 weeks of gestation.
Lining: It is lined in epithelium due to the amniotic membrane.
Herniation Recover: The gut herniation occurs between 7 to 10 weeks and resolves by 10 to 12 weeks.
Average Measurements:
- Length: 50-60 cm
- Diameter: 3.8 cm

Umbilical Artery:
- Arises from the fetal internal iliac vessels.
- Courses adjacent to the fetal bladder.
- Exits the umbilicus, becoming part of the umbilical cord.
Visual Representation: In sonography, the 3-vessel cord can appear like a "stack of coins" indicating a normal structure.

Structure: The placenta is a discoid organ weighing between 480-600 grams at delivery and usually measures 2-4 cm in anterior-posterior (AP) dimension.
Maternal Surface: Irregular and divided into areas called cotyledons by septae.
Fetal Surface: Smooth, covered by chorionic and amniotic membranes.
Formation: Developed by proliferation of chorionic villi and maternal decidua basalis.
Intervillous Spaces: These areas serve as the primary site for the exchange of oxygen, nutrients, and wastes between fetal and maternal blood.
Functional Units: Each functional part of the placenta is known as a cotyledon, with 2-20 cotyledons per placenta, making it a highly vascular organ.

Hormonal Activity: Functions include the conversion of fetal steroids to estrogen, secretion of progesterone, and secretion of human chorionic gonadotropin (hCG).
Exchange Mechanisms: Crucial for the exchange of oxygen, waste products, and nutrients between the fetus and mother.
Immune Protection: The placenta provides immune protection for the fetus.

Any condition that reduces uterine blood flow may impair maternal placenta circulation, which can lead to intrauterine growth restriction (IUGR). Examples include hypotension, renal disease, and smoking.

The location and position of the placenta relative to the uterine wall can be observed through imaging. An anterior placenta resides on the front side of the uterine wall, while a posterior placenta is situated on the back side.

Aging Changes: As the placenta matures, it displays structural changes which can be evaluated through a grading system:
- The grading helps assess gestational age, although the statistical correlation between gestational age and placental grade is generally weak.
- Grade III Placenta: Identification of a grade III placenta in the second or early third trimester can indicate placental insufficiency, particularly if there are maternal health complications.
- Thickness: The normal placental thickness is generally less than 5 cm in the AP dimension.

Grades (0-3):
- Grade 0: No calcifications; smooth chorionic surface (typically seen up to 30 weeks).
- Grade 1: Scattered calcifications; slight contouring of the chorionic surface (31-36 weeks).
- Grade 2: Presence of basal layer (basilar) calcifications (36-38 weeks).
- Grade 3: Basilar calcifications with interlobar septal calcifications, infarcts, and "fallout" areas (38+ weeks).

After the 40th week, placental maturity is significantly advanced.
If two different grades are present within the placenta, the highest grade is assigned.
Most term pregnancies generally have a placenta grading of I or II; only about 10-15% present as grade III. Over 50% of placentas show some degree of macroscopic calcifications after the 33rd week.

Composition: Made up of decidua basalis and portions of the myometrium, comprising maternal veins that drain the placenta.
Development: The RPC can be visualized as early as 14 weeks of gestation.
Sonographic Appearance: Appears as a hypoechoic area 1-2 cm deep to the placenta with possible venous channels (venous lakes). It is important to differentiate between hematoma and venous lakes.
Diagnostic Evaluation: A color Doppler evaluation can aid in assessing hypoechoic masses found within the RPC.