Final answer:
Dizygotic (non-identical) twins occur when two eggs are released and fertilized by two different sperm. Ultrasound markers suggestive of dizygotic twins include the presence of separate placentas, different genders, and different growth patterns.
Step-by-step explanation:
Dizygotic (non-identical) twins occur when two eggs are released during an ovulation cycle and fertilized by two different sperm. This results in two separate zygotes that develop into twins. There are several ultrasound markers that can suggest the presence of dizygotic twins:
- Dichorionic-Diamniotic Placenta: Dizygotic twins usually have separate placentas, meaning each twin has its own placenta.
- Different Gender: If the twins are of different sexes, it strongly suggests that they are dizygotic.
- Predictable Growth: Each twin in a dizygotic pair has its own growth pattern, which can be observed through ultrasound measurements. The growth patterns are typically different from each other.