Placenta & Hcg & Amniotic Fluid😍

Placenta

• Dimensions:
• Weight: 500 gm & 500 mL
• Diameter: 15-20 cm
• Placental weight = Fetal weight at 17 weeks
• Central thickness: 2.5-4 cm
• Placentomegaly:
• Placental thickness ≥4 cm
• Causes:
• Diabetes, GDM
• GTD
• Twin pregnancy, TTTS
• Rh negative pregnancy
• Small Placenta
• Pre eclampsia
• IUGR

GA	Placental Wt
At 17 weeks	Placental Weight = Fetal weight
At term	Ratio of placental weight to fetus = 1:6

• Formation:

ㅤ	Fetal side	Maternal side
Placenta formation	Chorion frondosum	Decidua basalis
Appearance	Smooth, shiny	Dull
During Placental separation	Central separation	Peripheral separation
Method	Schultze method	Duncan method
ㅤ	Better, M/c ↳ Retroplacental clot formed ↳ Decreased bleeding	ㅤ

• Features:
• Discoidal
• Deciduate: Shed off after delivery
• Hemochorial: Lies in contact with maternal blood

Placental Hormones

• M/c site of production : Syncytiotrophoblast.
1. hCG
2. HPL
• Cause: Insulin Resistance
• Fasting Hypoglycemia
• Postprandial Hyperglycemia
3. Progesterone

• From DHEA-S produced by fetal adrenal gland.
• Estriol (E3)

Human Chorionic Gonadotropin (hCG)

• Type: Glycoprotein hormone
• Also AMH/MIS → Glycoprotein hormone

• Secreted by Syncytiotrophoblast from implantation onwards

• Subunits:
• α-subunit: Similar to LH, FSH, TSH
• β-subunit:
• Similar to LH
• Specific
• Tested in UPT
• So structurally similar to LH

• Function:
• Maintains corpus luteum up to 6 weeks of pregnancy
• First stimulus for release of testosterone from fetal testis

• Doubling time: 48 hours

• Levels:
• Appears in blood: Day 8-9 after fertilization (D22 of cycle)
• Peak levels: 9-10 weeks
• Plateau: 16-20 weeks

• T1/2: 36 hours

Feature	hCG	LH
T½	37 hours	30 minutes
Potency	80X	X

• Functions:
• Stimulate the maternal thyroid gland during pregnancy.
• Stimulates Leydig cells → Testosterone production
• Stimulates corpus luteum → Relaxin production
• Exhibits immunosuppressive activity → Prevents fetal rejection
• Maintains corpus luteum up to 6 weeks of pregnancy

NOTE

Hormonal Changes in Pregnancy

Cervical Mucous Study

ㅤ	Estrogen	Progesterone
Consistency	Profuse, watery, elastic	Thick, scanty, viscous
Known as	Spinnbarkeit (Stretching ⊕) Spin → Loose	Tack (Stretching ⊝) Tack → katti
ㅤ	ㅤ	ㅤ

Ferning

• Seen under microscope on D8
• ↳ Proliferative phase

• Disappears by D18 of cycle

• If ferning persist by D18, indicates Anovulation

Endometrial Glands

• Endometrial Biopsy → Not commonly done for ovulation.

• Timing: D26 (Pre-menstrual phase).

 

Stages	Features
Early proliferative ↳ Estrogen	• Simple tubular glands • Telescoping of gland • Pseudostratification (Nuclei at different levels)
Early secretory ↳ Progesterone	• Subnuclear vacuolation: First sign of ovulation on biopsy (D17 - D18)
Late secretory ↳ Progesterone	• Corkscrew glands • Sawtooth appearance • Secretions in gland

Placental Anomalies

• Maternal side larger than fetal side

Placenta bilobata

• Equal size lobes

Placenta succenturiata

• Unequal lobes
• Connected by blood vessels.
• After delivery
• Placenta shows an oval defect in chorion
• with torn blood vessels ending abruptly at margins
• Complications
• Retained placenta  
• PPH



• Increased size of placenta 
• Increased risk of placenta previa → Antepartum hemorrhage (APH).

• Single umbilical cord

• Battledore placenta:
• Marginal insertion of cord

• Circumvallate placenta:
• Valve-like thickening
• A/w
• IUGR
• Placenta Previa
• Preterm labor

• Circummarginate placenta:
• No valve-like thickening

Velamentous Cord Insertion

Pathophysiology

• Cord attaches to membranes, not directly to placenta

• Wharton's jelly absent in membrane part

• Vessels run freely in membranes before reaching placenta

Complications

Vasa previa

• Unprotected vessels may rupture

• After ARM: Fetal distress + bleed.
• Less blood loss + marked fetal distress

• Leads to fetal blood loss → life-threatening

 

Types	A/w	Notes
1	Velamentous cord	ㅤ
2	Placenta Succinturiata	• Umbilical cord attached only to bigger lobe • Smaller lobe if left behind → cause PPH

Placental Transfer:

✅ Can Cross the Placenta

Nutrients

• Glucose – facilitated diffusion

• Amino acids – active transport

• Fatty acids – esp. long-chain

• Water-soluble Vitamins (e.g., B, C)

• Minerals – calcium, iron

Gases

• O₂ – maternal to fetal

• CO₂ – fetal to maternal

Water & Electrolytes

• Water, Na⁺, K⁺, Cl⁻ – passive/facilitated

Antibodies

• IgG – receptor-mediated (passive immunity)

• IgG2:
• Does not cross placenta
• protects against capsulated organisms

Hormones

• Cortisol, Thyroid hormones – limited crossing, regulated

Drugs

• Lipid-soluble, low MW (<500 Da)

• Examples: alcohol, nicotine, caffeine, some anesthetics, anticonvulsants, antidepressants

Toxins

• Alcohol, mercury, lead, pesticides

Pathogens

• Viruses: rubella, CMV, Zika

• Bacteria: Treponema pallidum

• Parasites: Toxoplasma gondii

❌Cannot / Limited Passage

Large Molecules

• Proteins – albumin, Hb

• IgM – too large

Hormones

• Insulin, LH, FSH, GH, TSH, HCG

• Peptide hormones – limited

• Catecholamines – degraded/metabolized

Some Drugs

• High MW (>1000 Da), polar

• Example: heparin

• Efflux by P-glycoprotein

Blood Cells

• RBCs, WBCs – normally blocked

• Rare: microtransfusion in placental injury

Most Bacteria

• Generally blocked

• Exception: Listeria

Placenta Accreta Spectrum (PAS)IOC →

IOC

Condition	Screening	IOC	ㅤ
Vasa Previa	ㅤ	USG Doppler	ㅤ
Placenta Previa	TAS (PP vs. AP)	TVS	Best Time for USG • T3 (32 - 36 weeks)
Placenta accreta	TVS	MRI	ㅤ

Signs on USG Placenta Accreta Spectrum:

• Placental lakes/moth-eaten appearance.

• Heterogenous Placenta

• Thinning of myometrium behind Placenta

• Loss of clear space behind Placenta

• Loss of Bladder line

• Absence Of hypoechoic area
• behind placenta representing decidua basalis

• Absence Of Continuous white line reflecting
• bladder - uterine serosa interface.

Types:

Types	Featuures
Placenta accreta (M/c)	Chorionic villi superficially attached to myometrium
Placenta increta	Villi invade myometrium
Placenta percreta	Villi penetrate → attached to serosa

Pathology:

• Absent decidua basalis.

• Absent Nitabuch layer.

Risk factors:

• Placenta previa +

• Previous history of C-section.

C/F

• Cord snapping on traction

• PPH

Management (Mx):

• Classical CS + Hysterectomy

 

Amniotic Fluid

• pH : 7 - 7.5

• Maximum at
• 32-34 weeks
• 1000 mL

• At term/40 weeks:
• 800 mL

• ≥42 weeks:
• 200 mL

Normal values

• AFI (Amniotic Fluid Index): 5 - 25 cm

• SVP (Single Largest Vertical Pocket): 2 - 8 cm

Source

• Gestational age: Source
• First trimester: Maternal plasma
• 12-20 weeks: Fetal skin
• 20 weeks: Fetal urine
• Mnemonic: Amniotic fluid → AFP → ammede blood, fetal skin, Peee

Appearance

• Straw coloured: Term

• Clear to pale yellow

• Without white specks
• White specks → indicate meconium staining
• Cloudy → Infection

Colour

• Colour: Seen in
• Saffron colour, yellowish green:
• Post term pregnancy
• Green colour (Due to biliverdin in meconium):
1. Fetal distress
2. Transverse lie/Breech
3. Listeria infection
• Mnemonic: Green → GB → Liver → LFT
• Golden colour (Due to bilirubin):
• Rh incompatibility
• Mnemonic: Gold (golden), Ruby (rubin) → Rich (Rh)
• Tobacco juice/Brown:
• Intrauterine fetal death
• Mnemonic: Tobacco brings death
• Dark red:
• Concealed hemorrhage

Listeria infection

• Cross placenta

• Make Amniotic fluid Green

• Shows differential motility

Amniotic Fluid Disorders

Oligohydramnios vs. Polyhydramnios

• Conditions leading to both oligo & polyhydramnios:
• TTTS
• TORCH infections

Oligohydramnios

• AFI: <5 cm

• Single largest vertical pocket (SVP): <2 cm

• M/c cause of mild oligohydramnios: Idiopathic

• M/c cause of severe oligohydramnios: 

Fetal renal anomalies	Notes
Renal agenesis / anomalies	• m/c
Posterior Urethral valve	ㅤ
UPI / PIH	• Decreased transudation across placenta (Small placenta) • Oligo in T3
Ruptured membranes	• Best: P/s examination
TORCH	• Early onset Oligohydramnios
IUD/ Post term baby	ㅤ

• Other causes:
1. Decreased urine output:
• Renal disorders
• Drugs: ACE inhibitors/Indomethacin
2. Decreased volume of Amniotic fluid:
• Post term pregnancy
• PROM
• Leaking after amniocentesis
3. Chromosomal Anomaly:
• (69 chr) Triploidy

• May lead to compression defects
• CTEV
• Potter’s syndrome / sequence

Polyhydramnios

• AFI: >25 cm

• SVP: >8 cm

• Mild Polyhydramnios: Idiopathic

• M/c cause of severe Polyhydramnios: 
• Fetal GIT anomalies
• Esophageal atresia
• Duodenal atresia
• Cleft lip/Cleft palate
• Anencephaly
• CDH

• Other causes:
1. Increased transudation across placenta:
• Placentomegaly
• Placental thickness ≥4 cm
• Causes:
• Diabetes, GDM
• GTD
• Twin pregnancy, TTTS
• Rh negative pregnancy
2. Increased urine output:
• Hydrops Fetalis
• Twin pregnancy, Diabetes, Bartter syndrome
• Fetal anemia (Thalassemia, Rh negative pregnancy, Parvo virus infection)
3. Increased transudation from fetal skin:
• NTD, Abdominal wall defect
4. Chromosomal anomaly:
• Trisomy

Approach to a Case of Polyhydramnios/Oligohydramnios

Note:

• PSV of MCA
• ≥ 1.5 MOM: Fetal anemia.
• < 0.8 MOM: Fetal polycythemia.

• Indomethacin:
• Can be used to treat polyhydramnios
• S/E: Premature closure of ductus arteriosus
• C/I: >32 weeks of pregnancy

Note:

1. M/c CTG Finding in oligohydramnios:
• Variable deceleration → Due to cord compression

2. Persistent variable deceleration:
• Only indication for amnioinfusion

Syndromes related to Oligohydramnios

Potters syndrome:

• Severe oligohydramnios due to kidney defects
• Renal agenesis
• B/L renal agenesis (incompatible with life).
• PCKD

• C/f:
• Lung hypoplasia
• most common cause of mortality in Potter syndrome
• Typical flat facies
• Potters sequence
• Severe oligohydramnios due to non renal causes

Clinical features:

• Extremities anomaly.
• Wrinkled skin.
• Facial dysmorphism.
• Renal agenesis B/L (primary anomaly).
• Oligohydramnios.
• Eyes widely separated.
• Epicanthic folds.
• Flat facies.
• High forehead.
• Receding chin.
• Washer man's hand.
• Potter facies.
 

 

Amniotic band syndrome

• Severe oligohydramnios due to PPROM
• C/f:
• Distal digit amputation
• Craniofacial abnormalities

Note:

• Proximal limb amputation:
• Phocomelia due to Thalidomide
• Mnemonic: Melathe (melia) kayyi poi (Proximallimb) → thali kettan (thalidomide) pattanilla

• Distal digit amputee
• Amniotic band syndrome
• Oligohydramnios

Presentation Of Oligohydramnios

• Early pregnancy:
• Lung hypoplasia,
• Limb amputation

• Late pregnancy:
• Cord compression
• Fetal distress
• Meconium aspiration syndrome
• Club foot/CTEV

Amniotic Fluid Embolism

• Diagnosis: Clinical diagnosis, no confirmatory test.

• Prognosis: Can lead to maternal mortality within 30-40 mins.

• Time of Occurrence: At the time of labour/within 30 mins of labour.

Phases:

• 1st Phase:
• Cardiorespiratory arrest (Difficulty breathing, ↑PR, ↓BP).
• pulmonary vasoconstriction and right ventricular failure.

• 2nd Phase:
• DIC + excessive bleeding.

Diagnostic Criteria:

• Unexplained shock + less bleeding.

• Clinical onset within 30 mins of labour.

• Abrupt cardiorespiratory arrest.

• Overt DIC.

• No fever.