Fetal Monitoring, Diagnostic Procedures, and Pre-eclampsia in Pregnancy

Posted on Aug 5, 2025 in Biomedical Sciences

Fetal Monitoring and Labor Stages

Ultrasound Examination

  • Purpose: Detects intrauterine infection, fetoplacental insufficiency, intrauterine growth restriction, fetal organ development, congenital anomalies, pregnancy diagnosis, placenta implantation (position, location, thickness), stage of labor, fetal lie, position, presentation, engagement, and size.
  • Anatomical Examination:
    • Biparietal diameter
    • Femur length
    • Transverse truncal diameter
    • Anterior-posterior truncal diameter
    • Front-occipital diameter
  • Functional Examination:
    • Amniotic fluid assessment for signs of fetoplacental insufficiency and infection.
    • Evaluation of meconium staining, suspended particles, fluid amount, and pockets.
    • Assessment of myometrial contractions, brain ventricle enlargement, internal organ development, and heart function (Dopplerometry).

Fetal Cardiotocography (CTG)

  • Purpose: Monitors fetal heart rate and uterine tone simultaneously.
  • Indications:
    • High-risk pregnancies
    • Suspected fetal distress
    • Evaluation of uterine contraction strength
    • Management of uterotonics
  • Types:
    • External CTG: Non-invasive, electrodes placed on the mother’s abdomen; less accurate.
    • Internal CTG: Invasive, uses an intrauterine pressure catheter (IUPC) and spiral electrode; more accurate but carries risks of infection and injury.

Fetal Biophysical Profile

  • Assessment: Evaluates fetal breathing movement, gross body movement, fetal tone, and heart rate.
  • Scoring: Each variable is scored as 2 (normal) or 0 (abnormal). The total score ranges from 0 to 10.
  • Biophysical Variables:
    • Fetal Breathing Movement: >1 episode for 30 seconds in 30 minutes (normal); absent or <30 seconds (abnormal).
    • Gross Body Movement: >3 movements in 30 minutes (normal); <3 movements (abnormal).
    • Fetal Tone: >1 episode of extension-flexion (normal); slow or absent (abnormal).
    • Reactive Fetal Heart Rate (FHR): >2 accelerations with fetal movement in 30 minutes (normal); <1 acceleration (abnormal).
    • Amniotic Fluid Volume: At least one pocket of fluid measuring >2 cm x 2 cm (normal); <1 pool of fluid or pool <1cm x 1cm (abnormal).

Preparatory Contractions and Pre-Labor Stages

  • Normal Preparatory Contractions: Invisible, painless, occur at night, and lead to cervical maturation.
  • Pathological Preliminaries Period (PPP): Characterized by painful contractions during the day and night, with no structural changes in the cervix before labor.

Preliminary Period (Pre-Labor Stage)

This stage may begin 2-3 weeks before the onset of labor.

Physiological Preliminary Periods:
  • Lightning: Incorporation of the lower uterine segment into the wall of the uterus.
  • False Labor Pain: Dull, confined to the lower abdomen and groin, not associated with hardening of the uterus.
  • Cervical Changes: The cervix becomes ripe a few days before the onset of labor, becoming soft and beginning effacement.
Pathological Preliminary Period:
  • Painful, irregular uterine contractions of various intensity, duration, and intervals, lasting >6 hours.
  • Absence of cervical dilation.
  • Patient cannot sleep at night due to pain, leading to tiredness and irritability.
  • Worsening of maternal and fetal condition.
  • Increased tonus of the lower segment of the uterus.
  • The presenting part is situated above the pelvic inlet and not engaged.
Treatment for Pathological Preliminary Period:
  • Premedication: 2 ml of 1% Promedol solution + 0.5 mg of Atropine + 10 mg of Seduxen + 10 mg of Pipolphen IV.
  • 20 ml of 20% solution of Natrium Hydroxybutyrate IV to induce sleep.
  • Spasmolytic agents.

True labor should begin after this treatment. If labor does not begin, repeat steps 2 and 3. If symptoms persist, a C-section may be necessary.

Advanced Diagnostic Procedures in Pregnancy

Amnioscopy

  • Description: Invasive examination to visualize the forebag of the amniotic sac and check for meconium staining. An amnioscope is introduced through the cervical canal.
  • Indication: Only performed in term pregnancies with a sufficiently dilated cervix.

Amniocentesis

  • Timing: Conducted between 16 and 18 weeks of gestation.
  • Procedure: Performed under ultrasound guidance. A needle is inserted through the mother’s abdomen into the amniotic sac to obtain amniotic fluid.
  • Uses: Collects fetal cells for cytogenetic analysis to diagnose chromosomal disorders and open neural tube defects (e.g., spina bifida).

Chorionic Villus Sampling (CVS)

  • Timing: Performed between 9 and 11 weeks of gestation.
  • Procedure: Conducted transabdominally or transcervically under sonographic guidance. A sterile catheter is inserted into the uterine cavity to aspirate chorionic villi for analysis.
  • Benefit: Can be performed earlier in gestation, allowing for potential termination of pregnancy in the presence of fetal abnormalities.

Cordocentesis (Fetal Blood Sampling)

  • Alternative Names: Fetal blood sampling or percutaneous umbilical blood sampling.
  • Timing: Conducted in the 2nd and 3rd trimesters.
  • Procedure: The umbilical cord is identified using sonography, and a sterile needle is inserted into umbilical vessels to obtain fetal blood.
  • Analysis: Analyzes fetal blood for chromosome abnormalities (e.g., Down syndrome) and blood disorders (e.g., fetal hemolytic disease).
  • Indications:
    • Malformations of the fetus
    • Fetal infections (e.g., toxoplasmosis, rubella)
    • Fetal platelet count in the mother
    • Fetal anemia

Pre-eclampsia: Definition, Risks, and Pathophysiology

Definition of Pre-eclampsia

Pre-eclampsia is a multisystem disorder of unknown etiology characterized by the development of hypertension (140/90 mmHg or more) with proteinuria after the 20th week of gestation in a previously normotensive and non-proteinuric patient.

Risk Factors for Pre-eclampsia

  • Multiple pregnancy
  • Antiphospholipid syndrome
  • Prolonged interval between pregnancies
  • Previous pre-eclampsia
  • Systemic hypertension
  • Family history of pregnancy-induced hypertension
  • Placental abnormalities (e.g., hyperplacentosis)
  • Maternal obesity
  • Chronic kidney disease
  • Diabetes
  • Polyhydramnios
  • Nulliparity
  • Advanced maternal age
  • Thrombophilias

Pathophysiology of Pre-eclampsia

Key mechanisms include hypercoagulation, hemoconcentration, and peripheral vasospasm, along with other contributing factors:

  • Peripheral Vasospasm: Constriction of blood vessels leading to hypertension.
  • Failure of Trophoblast Migration: Inadequate endovascular trophoblast migration reduces blood supply to the fetoplacental unit.
  • Prostaglandin Imbalance: Altered prostaglandin levels and increased thromboxane synthesis contribute to vascular issues.
  • Increased Sensitivity to Angiotensin II: Heightened response leads to proteinuria and loss of alpha-2 globulin.
  • Nitric Oxide Deficiency: Reduced synthesis impairs vascular relaxation and promotes thrombosis.
  • Endothelin-1 Production: Increased levels cause vasoconstriction and hypertension.
  • Inflammatory Mediators: Cytokines like TNF-alpha and IL-6 cause endothelial injury.
  • Abnormal Lipid Metabolism: Increased oxidative stress leads to endothelial dysfunction.
  • Angiogenic Imbalance: Overproduction of antiangiogenic factors (e.g., sFlt-1 and soluble endoglin) disrupts normal vascular function, leading to endothelial dysfunction through interactions with VEGF and PLGF.

Pelvic Outlet and Labor Presentation

A normal pelvic outlet should allow for an anterior-posterior presentation.

Diagnosis of Abnormal Labor Presentation:

  • Deep Transverse Arrest
  • Contracted Pelvis
  • Platypelloid Pelvis
  • Sagittal suture is in transverse diameter at pelvic outlet