Management of the Fetus and Newborn - Part 1

Management of the Fetus and Newborn

Overview of Topics

  • The management of the fetus and newborn.

  • The importance of blood bank testing for prenatal and postnatal assessments.

Prenatal Testing

Importance of Prenatal Testing

  • Assessing the risk of hemolytic disease of the fetus and newborn (HDFN).

  • Initial laboratory tests at the first prenatal visit are crucial for risk assessment.

Key Terminology

  • Neonate: Newborn from birth to four weeks of age.

  • Infant: Baby during the first year of life; terms "neonate" and "infant" are sometimes used interchangeably, which can cause confusion.

  • Gravid: Pregnant female.

  • Gravida: Number of pregnancies experienced by a woman; includes both births and non-births.

  • Para: Delivering a live infant; any multiple births count as a single para event.

  • Example: A female with "gravida two para one" has experienced two pregnancies and one live birth.

Blood Bank Testing for Prenatal Assessment

Objectives of Prenatal Blood Tests

  • Identify women at risk of HDFN by performing:

    • Blood type (ABO and Rh) testing.

    • Detection of clinically significant antibodies.

Clinically Significant Antibodies

  • Key antibodies to monitor:

    • D: Highly immunogenic and concerning for HDFN.

    • Kell: Also highly immunogenic and significant for risk assessment.

  • Less significant antibodies:

    • Lewis, P, Big I: Not well developed at birth; rare cases of HDFN.

Exchange Transfusion

  • Indicated for severe HDFN, treats anemia and hyperbilirubinemia.

  • Purpose: Correct anemia and reduce bilirubin levels due to red cell destruction.

  • May require special blood from blood banks.

Prenatal History Review

Importance of Prior Pregnancy History

  • Identifying outcomes of previous pregnancies: live births, stillbirths, miscarriages, transfusions.

  • Blood testing includes:

    • ABO typing

    • Rh typing (especially in Rh negative mothers).

    • Antibody screening to differentiate between IgG and IgM antibodies.

Antibody Screening and Identification

Process for Positive Results

  1. Conduct an antibody identification (ID) panel to identify antibodies present.

  2. Determine if the father has corresponding antigens.

    • Homozygous: Father has two copies of the antigen, increasing risk for the fetus.

    • Heterozygous: May require fetal genotype analysis using PCR techniques.

Antibody Titration

  • Antibody titer: Serial dilutions of maternal plasma to quantify antibody concentration.

    • Increase in titers indicates a higher risk for the fetus.

    • Baseline established in the first trimester.

    • Not entirely reliable as a predictor of disease severity.

  • Critical titers to watch for:

    • For D: A titer of 16 or 32 is critical.

    • For Kell: A titer greater than 8 is considered critical.

Methodology for Titer Testing

  • Test should usually be by tube method, as gel can yield invalid results.

  • Importance of saving the previous sample to enable parallel testing and reduce variability.

  • Adjusting for techniques and reagents that may lead to errors in results.

Other Prenatal Laboratory Tests

Tests for Infectious Diseases

  • Assess immunity to:

    • Rubella (German measles)

    • Varicella

    • HIV, Hepatitis (B and C)

    • Syphilis, Gonorrhea, Group B Strep

  • Urinalysis (UA) for urinary tract infections (UTIs).

Additional Screening Tests

  • Testing based on age, family history, and ethnicity, such as:

    • Toxoplasmosis

    • Screening for gestational diabetes.

    • Genetic testing for Down syndrome, cystic fibrosis, and other birth defects.

Fetal Monitoring Techniques

Monitoring for Hemolytic Disease

  • Middle cerebral artery peak systolic velocity (MCA PSV):

    • Non-invasive, measures fetal blood flow to diagnose anemia.

    • Effective for patients with a history of severely affected fetuses.

    • Taken every two weeks with no adverse fetal effects.

  • Cordocentesis (PUBS):

    • Invasive procedure where blood is obtained from the umbilical vein for analysis.

    • Testing includes hemoglobin, hematocrit, bilirubin levels, blood type, and DAT.

  • Amniocentesis:

    • Invasive testing for amniotic fluid could indicate fetal maturity and conditions like neural tube defects and genetic disorders.

    • Requires careful transport and specific analytical procedures.

Predicting Fetal Maturity with Amniotic Fluid Analysis

  • Creatinine test to differentiate amniotic fluid from urine.

  • Lamellar body count (LBC):

    • Predicts fetal lung maturity one of the breast indicators for respiratory distress in newborns.

    • LBC count > 50,000 is predictive of maturity, while < 15,000 suggests immaturity.

    • LS ratio analysis (Lecithin/Sphingomyelin) further confirms maturity but is labor-intensive.

    • Phosphatidylglycerol positivity indicates maturity post 35 weeks.

Testing for Fetal Well-being

  • Evaluating bilirubin concentration to assess fetal hemolysis risk.

  • Lily graph refers to bilirubin concentration trends related to the severity of HDFN;

    • Higher values correlate with increased severity of disease.

Management Strategies for Severe Cases

Intrauterine Transfusion

  • Performed only if risk of fetal demise is high or if ultrasound indicates significant anemia.

  • Requires accessing the fetal umbilical vein for blood infusion; repeat transfusion needed until delivery.

Blood Attributes for Transfusion

  • Blood must be irradiated to prevent graft-versus-host disease due to the baby's likely immunocompromised state.

  • Selection criteria include:

    • O negative and testing negative for relevant maternal antibodies.

    • Fresh donor blood is preferred, with a crossmatch using a current maternal sample.

Conclusion

  • Importance of regular monitoring and testing during pregnancy to identify and manage hemolytic disease effectively.