---

📘 Basics of Pregnancy: Part 1 - Complete Summary

---

1. Timelines & Key Presumptions

• Regular cycles
• Cycle length = 28 days
• Day 14 of cycle = Day of ovulation = Day of fertilization

Day 1 (LMP) ──────── Day 14 (Ovulation/Fertilization) ──────── Day 28 (Missed Period = 4th week of pregnancy)

• Pregnancy is always calculated from the 1st day of LMP (not from fertilization)
• The missed period at Day 28 corresponds to the 4th week of pregnancy (fertilization was 2 weeks prior)

---

2. Gestational Age vs. Fetal Age

• Key difference: Gestational age = Fetal age + 2 weeks
• Example: Cardiac activity appears at 3 weeks after fertilization = 5th week of pregnancy (gestational age)

Exam trick: A woman married Jan 1, fertilization Jan 14, missed period Jan 28, UPT positive Jan 29-30. She is 4 weeks pregnant (gestational age), NOT 2 weeks.

---

3. Trimesters (Calculated from 1st day of LMP)

---

4. Fetal Growth Periods (Embryologists' perspective - from day of fertilization)

Important note: Fetal growth period is the ONLY pregnancy event NOT calculated from 1st day of LMP. It uses the day of fertilization.

---

5. Calculation of EDD (Estimated Date of Delivery)

Naegele's Formula (Regular 28-day cycle / cycle not mentioned):

• LMP = 27 Dec 2023 → +7 days = 3rd Jan → +9 months = 3rd October 2024
• LMP = 25 Feb 2024 (Feb exception) → +9 months = 25 Nov → +7 days = 2nd Dec 2024

Cycle Length ≠ 28 Days:

1. Calculate approximate EDD using Naegele's formula
2. Find difference between given cycle and 28 days
3. Apply:
   • Cycle > 28 days → ADD the difference to EDD
   • Cycle < 28 days → SUBTRACT the difference from EDD
   • Example: Cycle = 32 days → difference = 4 days → EDD + 4 days

Naegele's Formula is NOT applicable in:

1. Pregnancy due to OCP failure
2. Lactational amenorrhea (women who conceived while breastfeeding)
3. Irregular cycles
4. Unsure about LMP

---

6. EDD in IVF

Fresh IVF Cycle:

• Day 14 of cycle = Day of fertilization = Day of oocyte retrieval
• EDD = Day of fertilization + 266 days (= 280 days total pregnancy)

Frozen IVF Cycle (Day of fertilization ≠ Day of oocyte retrieval):

• Day 3 transfer = Day 17 of cycle → EDD = Date of D3 transfer + 263 days (17 + 263 = 280 ✓)
• Day 5 transfer = Day 19 of cycle → EDD = Date of D5 transfer + 261 days (19 + 261 = 280 ✓)

---

7. Important Pregnancy Terminologies

Preterm Classification:

• Early preterm: < 34 weeks
• Late preterm: 34 weeks to 36 weeks + 6 days

• Late PTB: 34 - 36 wks + 6 days
• Moderate PTB: 32 - 33 wks + 6 days
• Very PTB: < 32 weeks
• Extreme PTB: < 28 weeks

---

8. Intrauterine Fetal Death (IUD) / Stillbirth

• Also called Stillbirth; death of fetus at ≥ 20 weeks
• WHO defines IUD as: fetal weight ≥ 500g; Stillbirth as ≥ 28 weeks

Most Common Causes:

• Idiopathic = most common overall
• Unrecognized IUGR = most common single identifiable cause

Diagnosis:

• Patient presents with loss of fetal movements
  • ≥ 32 weeks → Modified BPS (Biophysical Profile Score) or NST
  • < 32 weeks → USG

USG Signs of IUD:

1. Absence of cardiac activity
2. Spalding sign - Collapse of fetal skull (overlapping of skull bones)
3. Robert's sign (1st sign to appear) - Gas bubbles in great vessels of fetus
4. Ball sign - Hyperflexion/hyperextension of fetal spine (vertebral column looks like a ball)
5. Crowding of ribs
6. Amniotic fluid: Tobacco juice colour

Complication:

• DIC (rare) - Risk factor: dead fetus retained for ≥ 4 weeks
• Practical tip: If IUD diagnosed 2-3 weeks back → do coagulation profile

Management:

• Preferred mode: Vaginal delivery (spontaneous labour or induction)
• C-section indications: Placenta previa, Transverse lie, Obstructed labour, ≥ 2 previous LSCS

---

High-Yield Points to Remember 🔑

1. Pregnancy duration = 40 weeks / 280 days - calculated from 1st day of LMP
2. Gestational age is always 2 weeks more than fetal age
3. Cardiac activity at 21 days post-fertilization = 5th week of pregnancy
4. Naegele's formula: add 7 days first, then 9 months (exception: February LMP - reverse order)
5. IVF EDD formula always adds up to 280 days total
6. Abortion = loss < 20 wks; IUD/stillbirth = loss ≥ 20 wks
7. ACOG preterm classification is most used: Early preterm < 34 wks, Late preterm 34-36+6 wks
8. Most common cause of IUD = idiopathic; Robert's sign = first USG sign
9. DIC risk when dead fetus retained ≥ 4 weeks
10. Vaginal delivery is preferred in IUD unless specific C-section indications exist