11/07/2025
Conjoined twins, also known as **Siamese twins**, are identical twins who are physically connected at birth. This rare condition occurs when a single fertilized egg (monozygotic) partially splits during early embryonic development, typically between days 13 and 15 after conception, resulting in twins that share some body structures.
# # # **Key Facts About Conjoined Twins:**
1. **Rarity**:
- Occur in about **1 in 50,000 to 200,000 births**.
- Many conjoined twins are stillborn or do not survive long after birth.
- About **40–60%** are born alive, and **35%** survive long enough for possible separation surgery.
2. **Types of Conjoined Twins (Based on Attachment Site)**:
- **Thoracopagus (most common, ~35%)** – Joined at the chest, often sharing a heart.
- **Omphalopagus (~30%)** – Joined at the abdomen, may share a liver.
- **Pygopagus (~18%)** – Joined at the lower spine/buttocks.
- **Ischiopagus (~6%)** – Joined at the pelvis, may share lower digestive/genital organs.
- **Craniopagus (~2%)** – Joined at the head (very complex to separate).
- **Parapagus (~5%)** – Side-by-side fusion, often sharing a pelvis and limbs.
- **Rarer forms**: Rachipagus (spine), Cephalopagus (head and chest).
3. **Causes**:
- The exact cause is unknown, but it is believed to be a random developmental anomaly.
- Not hereditary or linked to environmental factors.
4. **Diagnosis**:
- Often detected via **ultrasound** during pregnancy.
- Further imaging (MRI, echocardiography) helps assess shared organs.
5. **Separation Surgery**:
- Possible only if both twins can survive independently.
- High-risk, requiring extensive planning by a multidisciplinary team.
- Success depends on the extent of shared organs (especially heart, brain, liver).
6. **Famous Cases**:
- **Chang & Eng Bunker (1811–1874)** – The original "Siamese twins," from Thailand (then Siam), lived to adulthood and had families.
- **Abigail & Brittany Hensel (born 1990)** – Dicephalic parapagus twins who share one body but have two heads.
- **Ladan & Laleh Bijani (1974–2003)** – Craniopagus twins who died during separation surgery.
# # # **Ethical & Medical Challenges:**
- If separation is impossible or life-threatening, parents may choose palliative care.
- In cases where one twin is weaker, doctors may face difficult decisions about sacrificing one to save the other.
