Dicigóticos

Dicigóticos, also known as dizygotic twins or fraternal twins, are twins that develop from two separate fertilized ova. They are genetically as related as any pair of siblings, sharing about 50 percent of their nuclear DNA, and they can be of the same or different sexes.

Origin and development: Dizygotic twinning occurs when two eggs are released and fertilized independently by two sperm cells during the same pregnancy. This contrast with monozygotic twins, who come from a single fertilized egg that splits. Dizygotic twins typically have two separate placentas and chorions and two amniotic sacs (diamniotic, dichorionic), though placental tissue can fuse during development, sometimes giving the appearance of a single placenta.

Incidence and factors: The likelihood of dizygotic twinning varies by population and individual factors. Rates are higher among people of African descent and lower among people of Asian descent. Maternal age, parity, and the use of assisted reproductive technologies also increase the chances. Globally, dizygotic twinning occurs in roughly 8–12 per 1000 deliveries, with considerable regional variation, and in many populations about 1 in 80 births.

Clinical considerations: Dizygotic twinning is associated with higher risks typical of multiple pregnancies, such as preterm birth and low birth weight, and a higher likelihood of cesarean delivery compared with singleton pregnancies. Because dizygotic twins usually have two placentas, they are generally not at risk for twin‑to‑twin transfusion syndrome, a complication more common in monochorionic, single-placenta twins.