OBSTETRICS

Antenatal care

October 3, 2023 / No Comments

First Visit (Booking Visit)

History and Assessment

  1. Symptoms of Pregnancy
    Document patient’s presenting symptoms such as amenorrhea, nausea, vomiting, fatigue, breast tenderness, etc.
  2. Menstrual History
    • Last Menstrual Period (LMP).
    • Cycle characteristics: duration, regularity, and frequency.
  3. Obstetric History
    • Number of pregnancies (Gravida) and outcomes (Parity).
    • History of live births, miscarriages, stillbirths, ectopic pregnancies, terminations, preterm births.
    • Complications in previous pregnancies (e.g., pre-eclampsia, gestational diabetes).
  4. Gynecological History
    • History of menstrual disorders, pelvic inflammatory disease (PID), fibroids, endometriosis, etc.
    • History of cervical screening and results.
  5. Past Medical History (PMHx)
    • Any chronic illnesses (e.g., hypertension, diabetes, autoimmune diseases).
  6. Surgical History
    • Prior abdominal, gynecological, or significant surgeries.
  7. Family History (Fhx)
    • Inherited diseases (e.g., cystic fibrosis, fragile X).
    • Genetic disorders, chromosomal abnormalities, history of congenital defects.
  8. Sociodemographic Information
    • Age, ethnicity, marital status, occupation, and social support system.
    • Cultural/religious beliefs impacting health care.
  9. Lifestyle Assessment
    • Smoking, alcohol, recreational drug use.
    • Physical activity and diet.
  10. Medications and Allergies
    • Current prescription and over-the-counter medications.
    • Document known allergies, especially to medications.

Physical Examination

  1. General Assessment:
    • Weight (Wt) and Height (Ht) – Calculate BMI.
    • Blood Pressure (BP) measurement.
    • Teeth and Gums – Assess oral health.
    • Thyroid – Palpation for goiter or nodules.
    • Breast Examination – Check for masses or nipple changes.
    • Chest and Heart – Auscultation for any abnormalities.
    • Abdominal Examination – Assess for masses, tenderness, fundal height (if applicable).
    • Pelvic Examination – If indicated, including cervical assessment.

Initial Investigations

  1. Routine Blood Tests:
    • Beta-hCG – Confirm pregnancy.
    • Full Blood Count (FBC) – Check hemoglobin, WBC, platelets.
    • ABO and Rh Blood Group with Antibody Screening.
    • Iron Studies – Ferritin, serum iron.
    • Rubella Immunity Status – Determine vaccination status.
    • Syphilis Serology – Consider repeat screening if high prevalence area.
    • Hepatitis B and C Serology.
    • HIV Serology.
    • Urine Microscopy, Culture, and Sensitivity (MCS).
  2. Ultrasound Scan:
    • Dating Scan – Transvaginal or Transabdominal ultrasound for accurate gestational dating.
  3. High-Risk Screening (if indicated):
    • HbA1c – If random glucose >5.5 mmol/L, perform a 75g Glucose Tolerance Test (GTT); HbA1c acceptable if GTT impractical.
    • Sexually Transmitted Infections (STI) Screening – First-pass urine PCR for Chlamydia, Gonorrhoea, Trichomoniasis, and Mycoplasma genitalium.
  4. Optional Investigations (if indicated):
    • Vitamin D – If Indigenous, dark skin, obesity, or minimal sun exposure.
    • Vitamin B12 – For vegetarians or if indicated.
    • Thyroid Function Tests (TFTs) – For symptomatic or high-risk women.
    • Chlamydia Screening – For women under 25 or in high-prevalence areas.
    • Gonorrhoea Testing – If risk factors are present.
    • Early OGTT (Glucose Tolerance Test) <20 weeks – If PCOS or other risk factors for gestational diabetes.
    • Cytomegalovirus (CMV) Immunity Testing – If frequent contact with young children.
    • Lead Levels, Varicella Zoster Immunity, and Strongyloides Serology (if indicated).
    • Methicillin-Resistant Staphylococcus Aureus (MRSA) Screening – Two sets of swabs if previously MRSA positive.

Supplement Recommendations

  1. Folic Acid:
    • 0.5 mg daily – Standard recommendation.
    • 5 mg daily – If BMI >30, malabsorption risk, pre-pregnancy diabetes, risk factors for neural tube defects (NTDs), family history of congenital heart disease, MTHFR mutation, or multiple pregnancy.
  2. Iodine – 150 mcg/day.
  3. Multivitamin Supplementation – If prior bariatric surgery.
  4. Calcium – Ensure a daily intake of 1000 mg.
  5. Iron – Routine supplementation is not recommended unless deficiency is confirmed. Emphasize iron-rich foods (e.g., red meat, tofu, iron-fortified cereals) and vitamin C-rich foods for absorption.

Lifestyle and Dietary Advice

  1. Toxoplasmosis Prevention – Hand washing, avoid raw/undercooked meat, avoid cat litter.
  2. Listeriosis Prevention – Wash fruit/vegetables thoroughly; avoid foods made >24 hours ago unless reheated to steaming hot; consume freshly cooked hot food immediately.
  3. Cytomegalovirus (CMV) Prevention – Avoid contact with saliva and urine of young children.
  4. BMI and Weight Management – Discuss risks of excess weight gain: GDM, pre-eclampsia, macrosomia, etc.

Pre-pregnancy BMI (kg/m2)Rate of weight gain 2nd and 3rs trimester (kg/week)Recommended total weight gain range (kg)
<18.5 underweight0.5112.5 to 18
18.5 to 24.9 normal weight0.4211.5 to 16
25.0 to 29.9 overweight0.287 to 11.5
≥ 30.0 obese0.225 to 9

Subsequent Visits

  1. Review Events Since Last Visit:
    • Pain, bleeding
    • discharge
    • fetal movements
    • concerns.
  2. Physical Examination:
    • BP
    • abdominal examination (fundal height, fetal lie, heart sounds)
    • lower limb edema
    • urinalysis (bacteriuria, glucose, protein).
  3. Investigations and Screening:
    • Consider family health history, address any concerns raised.

Screening Questions for Antenatal Care

  • Are there any conditions in your family that have affected multiple family members?
  • Has anyone in your family been born with a health or learning disability?
  • Has any family member experienced more than three miscarriages?
  • Is there a history of stillbirth or the death of a baby in your family?
  • Has anyone in your family required attendance at special schools or classes?
  • Is there anything you are particularly worried about regarding your pregnancy or family history?
    (While this may not directly assess family history, it can reveal additional concerns or overlooked information.)

First and Second Trimester Evaluations

Conditions to Assess:

  • Down Syndrome (Trisomy 21): Approximately 1 in 500 risk.
  • Edwards Syndrome (Trisomy 18): Approximately 1 in 3000 risk.
  • Patau Syndrome (Trisomy 13).
  • Open Neural Tube Defects (NTDs): Approximately 1 in 750 risk.

Risk Assessment Considerations:

  • If high risk, offer diagnostic testing (e.g., Chorionic Villus Sampling (CVS) or Amniocentesis).
  • Diagnostic tests carry a small risk of miscarriage (~0.5-1%).
  • Direct diagnostic testing may be warranted for significant risk factors.

Increased Risk Factors:

  • Advanced maternal age.
  • Previous pregnancy with chromosomal abnormalities.
  • Parental chromosomal rearrangement.
  • Medical history of both partners, including inherited conditions (e.g., cystic fibrosis, fragile X syndrome).
  • Family history of chromosomal conditions and birth defects (e.g., spina bifida, cleft lip/palate, cardiac anomalies).
  • Intellectual disabilities or history of recurrent miscarriages or unexplained perinatal deaths.
  • Ethnic background considerations for inherited conditions (e.g., thalassemia, cystic fibrosis).

Pros and Cons of Screening:

  • Pros:
    • Early Screening (First Trimester): High sensitivity and non-invasive.
    • Avoidance of Invasive Tests: Particularly beneficial for older women.
    • Accurate Dating: Early ultrasound for precise gestational age.
  • Cons:
    • Potential for Diagnostic Testing with increased miscarriage risk.
    • Complexity of Results: Probability-based results may be challenging.
    • Costs: Screening tests may have financial implications.
    • Unanticipated Findings: Results may lack clear clinical significance.
    • Anxiety: Positive results lead to follow-up testing and stress.
    • Multiples: Screening is feasible for twins, but not for higher-order multiples.

Recommended Tests:

First Trimester Screening (10-13 weeks):

  • Non-Invasive Prenatal Testing (NIPT) (10 weeks onwards to 18 weeks):
    • Screens for trisomy 21, 18, and 13 using cfDNA in maternal blood.
    • High Sensitivity and Specificity with lower false-positive rates compared to traditional serum and ultrasound screening.
    • Results classified as high risk or low risk using statistical algorithms; typical cut-off ~1 in 300.
  • Nuchal Translucency (NT) Scan (11-13 weeks):
    • Measures nuchal translucency (fluid behind the fetal neck).
    • Combined with serum markers (free β-hCG, PAPP-A) for improved detection.
    • CRL (Crown-Rump Length): 45-84 mm required for accurate NT measurement.
    • Nasal Bone Assessment may add predictive value.
    • NT measurement : <2 mm is often considered low risk, but risk stratification may also depend on maternal age and other variables.
    • Sensitivity Rates:
      • Down Syndrome (Trisomy 21): ~90%
      • Trisomy 18: ~80%
      • Anencephaly: High detection in first trimester.
      • Spina Bifida: Detected more reliably in the second trimester morphology scan (18-20 weeks).
      • False Positive Rate: Typically around 5% for combined first-trimester screening. This means 1 in 20 women may have a positive result, but most will not have an affected fetus.

Second Trimester Screening (14-20 weeks):

  • Quadruple Test (15-17 weeks):
    • Screens for chromosomal abnormalities (trisomy 21, 18) and NTDs using alpha-fetoprotein (AFP).
    • Components: AFP, free β-hCG (or total hCG), unconjugated estriol (uE3), inhibin A (varies by lab).
    • Detection Rates:
      • Neural Tube Defects: ~80%.
      • Down Syndrome: ~66%.

Next Steps for Increased Risk:

  • Chorionic Villus Sampling (CVS): Performed from 12-13 weeks, miscarriage risk ~1-2%.
  • Amniocentesis: From 15 weeks, miscarriage risk ~0.5-1%.

Additional Testing & Milestones:

  • Morphology Scan (18-20 weeks): Comprehensive assessment for fetal anomalies.
  • Glucose Tolerance Testing (24-28 weeks): Screening for gestational diabetes.
  • Vaccination and Blood Tests (28 weeks):
    • Influenza and dTpa (Diphtheria, Tetanus, Pertussis) vaccinations.
    • Rh Antibody Testing and Anti-D prophylaxis for Rh-negative women at 28 and 34 weeks.
  • 34 Weeks: Rh antibody testing and indicated ultrasounds for growth assessment.
  • 35-37 Weeks:
    • Screening for STIs if high risk
    • LVS for Group B Streptococcus (GBS)
  • Ultrasound (if indicated) for
    • hypertensive disorders
    • diabetes
    • intrauterine growth restriction (IUGR)
    • malpresentation.

Overview of NIPT

  • NIPT is a screening tool for detecting common aneuploidies (e.g., trisomy 21, 18, 13) using cell-free DNA (cfDNA) from the placenta, circulating in maternal blood.
  • Typically performed from 10 weeks gestation onward.
  • Involves analysis of fetal fraction of cfDNA (~10% at 10 weeks).

Accuracy and Sensitivity/Specificity:

  • Trisomy 21: Sensitivity ~99%, Specificity ~99.9%.
  • Trisomy 18: Sensitivity ~97-98%, Specificity ~99.8%.
  • Trisomy 13: Sensitivity ~91-96%, Specificity ~99.7%.
  • Sex Chromosome Aneuploidies: Lower sensitivity and specificity; detection rates vary.
  • False Positive Rate (General): Approximately 0.1-0.5%.

Factors Influencing NIPT Accuracy:

  1. Low Fetal Fraction:
    • Often due to high maternal BMI.
    • May lead to “no result” or lower accuracy
    • is reported in 1–2% of pregnancies
    • if it happens suggest repeat testing, alternative strategies for screening, or diagnostic testing
  2. Multiple Pregnancies (Twins):
    • Less accurate due to complexities in cfDNA origin.
    • Presence of a vanished twin can alter results.
  3. Maternal Conditions:
    • Chromosomal abnormalities, recent bone marrow transplant, or malignancy may affect cfDNA analysis.
  4. Discordant Genotypes:
    • Differences between fetal and placental DNA (e.g., placental mosaicism, fetal mosaicism).

Test Characteristics and Limitations:

  • Screening Tool: Provides a risk assessment, not a definitive diagnosis.
  • High-Risk Results: Require confirmatory testing (amniocentesis or chorionic villus sampling).
  • Low-Risk Results: Do not guarantee the absence of chromosomal abnormalities, particularly if prior probability is high.
  • Microdeletions: Limited data and lower accuracy for detecting these conditions.
  • Does Not Detect:
    • Rare chromosomal abnormalities (potentially detected via ultrasound or maternal markers in combined first trimester screening).
    • Single gene disorders (e.g., fragile X, cystic fibrosis).
    • Non-genetic conditions (e.g., neural tube defects, congenital cardiac anomalies).

Recommended Use:

  • Ultrasound (USS) is recommended alongside NIPT.
  • Clinical Pathways:
    • FTS (First Trimester Screening) preferred for twins due to limited NIPT reliability.
    • Follow-Up for “No Result” NIPT:
      • Consider detailed USS, combined FTS, second trimester screening, invasive testing, or repeating NIPT if appropriate.

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