Obgyn · Year 3 · from Obgyn

Case 1: First Prenatal Visit and Pregnancy Dating

Patient Demographics

  • Age: 28 years
  • Sex: Female
  • Occupation: Elementary school teacher

Chief Complaint

"I think I'm pregnant. I missed my period two weeks ago and had a positive home pregnancy test."

History of Present Illness

The patient reports her last menstrual period was 6 weeks ago. Her cycles are typically 28 days and regular. She has had mild nausea in the mornings but no vomiting. She denies vaginal bleeding or pelvic pain. This would be her first pregnancy. She takes a daily multivitamin but no prescription medications. She denies tobacco, alcohol, or drug use.

Past Medical History

  • No significant medical conditions
  • No prior surgeries
  • No known drug allergies

Obstetric History

  • G1P0 (first pregnancy)

Physical Examination Findings

  • Vital Signs: BP 118/72 mmHg, HR 76 bpm, BMI 24 kg/m2
  • General: Well-appearing female in no distress
  • Thyroid: Normal size, no nodules
  • Breast: No masses, no discharge
  • Abdomen: Soft, non-tender, non-distended
  • Pelvic: Cervix appears bluish (Chadwick sign), uterus slightly enlarged, no adnexal masses

Diagnostic Workup

  • Urine pregnancy test: Positive
  • Serum beta-hCG: 28,500 mIU/mL
  • Transvaginal Ultrasound: Single intrauterine gestational sac with yolk sac and embryo with crown-rump length of 8 mm, consistent with 6 weeks 4 days gestation; fetal cardiac activity present at 120 bpm
  • Hemoglobin: 12.8 g/dL
  • Blood Type: A positive
  • Antibody Screen: Negative
  • Rubella: Immune
  • Hepatitis B Surface Antigen: Negative
  • HIV: Negative
  • RPR: Non-reactive
  • Urinalysis: Normal, culture negative

Diagnosis

Intrauterine Pregnancy at 6 weeks 4 days gestation by crown-rump length measurement

Estimated Date of Delivery: Calculated using Naegele's rule and confirmed by first-trimester ultrasound

Management Plan

Initial Visit Counseling:

  1. Folic acid supplementation 400-800 mcg daily (already in prenatal vitamin)
  2. Dietary counseling: avoid raw fish, unpasteurized dairy, deli meats, high-mercury fish
  3. Avoid alcohol, tobacco, and recreational drugs
  4. Continue prenatal vitamins
  5. Return in 4 weeks for routine prenatal visit

Prenatal Visit Schedule:

  1. Every 4 weeks until 28 weeks
  2. Every 2 weeks from 28-36 weeks
  3. Weekly from 36 weeks until delivery

First Trimester Screening:

  • Offer nuchal translucency ultrasound at 11-14 weeks with PAPP-A and free beta-hCG
  • Discuss cell-free DNA screening as an alternative

Counseling Points:

  • First trimester fatigue and nausea are normal and typically improve by 12-14 weeks
  • Fetal heart tones audible by Doppler at 10-12 weeks
  • Anatomy ultrasound planned for 18-22 weeks
  • Warning signs to report: heavy vaginal bleeding, severe abdominal pain, fever

Clinical Image

Image Description: Transvaginal ultrasound image demonstrating a first-trimester embryo with crown-rump length measurement. The gestational sac is visible with the yolk sac adjacent to the embryo. This measurement provides the most accurate dating in early pregnancy.

Attribution: Image from Radiopaedia. Case courtesy of Dr. Mohammad Taghi Niknejad. Licensed under CC BY-NC-SA 3.0. Source: https://radiopaedia.org/cases/normal-first-trimester-pregnancy

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