Conjoined Twins – Symptoms and Causes
What Are Conjoined Twins?
Conjoined twins are babies born physically attached to each other. This happens when an early embryo doesn’t fully split into two separate individuals during development.
The twins remain connected, most commonly at the chest, abdomen, or pelvis, and they may share one or more internal organs.
Many conjoined twins don’t survive birth or live only briefly afterward. However, medical advances have improved survival rates. Some conjoined twins can be separated through surgery, though success depends on three key factors:
- Where the twins are joined
- Which and how many organs they share
- The surgical team’s expertise and experience
The connection between conjoined twins forms very early in pregnancy when the developing embryo only partially divides. Unlike typical twins who develop separately, conjoined twins remain physically linked throughout development and after birth.
Symptoms
A twin pregnancy where the babies are connected to each other doesn’t show special signs different from regular twin pregnancies. You might notice your belly grows faster than with one baby.
Some parents also feel more tired and have worse morning sickness early on. Doctors can find conjoined twins during pregnancy using ultrasound pictures.
How Connected Twins Are Joined
Doctors group connected twins by where their bodies meet. Each pair is different, and they might share organs or body parts. Here are the common ways twins can be connected:
Chest Connection (Thoracopagus)
- Twins face each other and join at the chest
- Often share one heart
- May share liver and upper digestive tract
- One of the most common types
Belly Connection (Omphalopagus)
- Joined near the belly button
- Often share the liver
- May share parts of the digestive system
- Usually have separate hearts
Lower Spine Connection (Pygopagus)
- Joined back-to-back at the base of the spine
- May share the lower digestive tract
- Sometimes share urinary and reproductive organs
Full Spine Connection (Rachipagus)
- Connected back-to-back along the entire spine
- Very rare type
Pelvic Connection (Ischiopagus)
- Joined at the pelvis
- Can be face-to-face or end-to-end
- They often share lower digestive tract, liver, and urinary organs
- Might have 2-3 legs between them
Side Connection (Parapagus)
- Joined side-by-side at the pelvis and trunk
- Separate heads
- Can have 2-4 arms and 2-3 legs
Head Connection (Craniopagus)
- Joined at the back, top, or side of the head
- Share part of the skull
- Usually have separate brains with some shared tissue
Head and Chest Connection (Cephalopagus)
- Joined at the head and upper body
- Faces appear on opposite sides of one shared head
- Share brain tissue
- Rarely survive
In unusual cases, one twin might be smaller and less developed than the other. This is called asymmetric connected twins. In extremely rare situations, doctors might find parts of one twin developing inside the other twin’s body.
Causes
Identical twins form when a fertilized egg divides into two separate embryos. These embryos typically develop independently. However, conjoined twins develop through a different process.
Scientists believe conjoined twins occur in one of two ways:
Incomplete Separation: When an embryo splits 13-15 days after conception (later than normal), the separation process may not finish completely.
Embryonic Fusion: Two separate embryos might somehow merge together during early development.
The exact reason why either of these situations happens remains unknown.
Between 8-12 days after conception, embryonic layers normally begin developing into specific body structures and organs. This timing appears crucial in determining whether twins will be separate or conjoined.
Risk Factors
The exact cause of conjoined twins remains unclear due to their rarity. Scientists have not identified specific factors that might increase the likelihood of having conjoined twins. Research continues to investigate this uncommon occurrence.
Complications
Pregnancy involving conjoined twins presents significant challenges. These rare pregnancies carry elevated risks compared to single or separate twin pregnancies.
Conjoined twins typically require delivery via C-section due to their physical connection. Premature birth is common with conjoined twins, which adds further health risks. Tragically, stillbirth or early infant death affects many conjoined twin pregnancies.
Immediate health concerns may include:
- Respiratory difficulties
- Cardiac complications
- Shared organ dysfunction
Long-term issues that may develop include:
- Scoliosis (spinal curvature)
- Cerebral palsy
- Learning and developmental challenges
The specific complications vary based on:
- Connection point between the twins.
- Which organs or body systems are shared.
- Available medical expertise.
Thorough discussions between healthcare providers and family members are essential when expecting conjoined twins. These conversations should cover potential complications and create comprehensive care plans. Advance preparation allows for better management of these complex cases.
