This leads to unequal levels of amniotic fluid between each fetus and usually leads to death of the undersupplied twin and, without treatment, usually death or a range of birth defects or disabilities for a surviving twin, such as underdeveloped, damaged or missing limbs, digits or organs (including the brain), especially cerebral palsy.

While TTTS has occasionally been detected beyond this timepoint, it is thought that its occurrence beyond week 30 may be due to a placental embolism that upsets the flow balance of the shared connections between the babies.

[citation needed] The fetal demise of one of the twins during the second trimester of a monochorionic pregnancy can result in serious complications to the surviving fetus.

Complications include gangrenous limbs, hands and feet, cerebral palsy and IQ deficits, constriction rings of limbs and digits, reduced digits, skin defects, brain cysts, hydranencephaly, multicystic encephalomalacia, microencephaly, renal agenesis and bowel atresia.

Stage IV: In addition to all of the above findings, the recipient twin has swelling under the skin and appears to be experiencing heart failure (fetal hydrops).

This procedure is associated with a 66% survival rate of at least one fetus, with a 15% risk of cerebral palsy, and average delivery occurring at 29 weeks' gestation.

In addition, tearing the dividing membrane has contributed to cord entanglement and demise of fetuses through physical complications.

This procedure has been associated with 85% survival rate of at least one fetus, with a 6–7% risk of cerebral palsy and average delivery occurring at 32–33 weeks' gestation.

[9][10] The pathogenesis of TAPS is based on the presence of few, minuscule arterio-venous (AV) placental anastomoses (diameter <1mm)[11] allowing a slow transfusion of blood from the donor to the recipient and leading gradually to highly discordant Hb levels.

[12] A 2014 review found that laser coagulation resulted in fewer fetal and perinatal deaths than amnioreduction and septostomy, and recommended its use for all states of TTTS.

This procedure involves the ligation or otherwise occlusion of one twin's umbilical cord to interrupt the exchange of blood between the fetuses.

The procedure is typically offered in cases where one of the fetuses is presumed moribund and endangering the life or health of the other twin through resultant hypotension.

Since spontaneous pregnancy losses and terminations that occur prior to 20 weeks go uncounted by the C.D.C., this estimate of TTTS cases may be very conservative.

Although infertility treatments have increased the rate of multiple birth, they have not appreciably diluted the expected incidence of identical twins.

This distinction could be partly explained by the "hidden mortality" associated with MC multifetal pregnancies—instances lost due to premature rupture of membrane (PROM) or intrauterine fetal demise before a thorough diagnosis of TTTS can be made.

Analysis of the family histories of the owners of the painting suggests that the twins did not survive to adulthood, although whether that is due to TTTS is uncertain.