Heteropagus conjoined twins (also known as parasitic twins) are defined as the presence of a nonviable and severely impaired fetus (or fetal parts) attached to a relatively normal twin
(termed the autosite) in one of the same areas in which intact conjoined twins would be united .
This is a relatively safe procedure overall but it carries risks such as ruptured membrane and damage to the normal twin
Twin pregnancy with one normal twin
and one complete hydatidiform mole: the normal twin
usually has its own normal placenta.
The Sahara's engines were the normal twin
cylinder units, each producing 12hp and each with a separate fuel tank.
Results: Out of 875 patients, 75(8.57%) were with no pregnancy, 501(57.25%) with normal single pregnancy, 5(0.57%) with abnormal single pregnancy, 18(2.05%) with normal twin
pregnancy, 2(0.22%) with abnormal twin pregnancy, 4(0.45%) with normal triplets.
The oldest and the most persistent theory of visceral inversion is that twins are often mirror image of each other that a single individual with situs inversus represents a survivor whose normal twin
has died in utero.
Mrs Garret, aged 26, now faces a wait to see if the normal twin
will survive the trauma of surgery.
1: Ultrasound image of Monochorionic (white arrow) Monoamniotic twin gestation Pelvis and lower limbs of normal twin
(*) and subcutaneous soft tissue surrounding the trunk of the pump twin (black arrow).
A reversed arterial flow was noted on Doppler study coming from apparently normal twin
to abnormal twin, fig (2) Diagnosis of TRAP sequence made.
The umbilical cord of the normal twin
was 20 cm with central attachment, while the other umbilical cord was 10 cm long with peripheral attachment.
 Blood from the normal twin
reaches the acardia through a large artery-artery anastomosis, flows through the acardia in reverse course and returns to the pump twin via a large vein-vein anastomosis.
Conjoined twins result from incomplete separation of monozygotic, monochorionic twins early in embryonic development, resulting in body parts of the otherwise normal twins
remaining fused throughout development.