]> 2026-07-31T07:52:06+00:00 WBR0333 0 en Dichorionic diamniotic twin pregnancy Dichorionic diamniotic twin pregnancy occurs when cleavage takes place between 0-4 days post-fertilization. Monochorionic diamniotic twin pregnancy Monochorionic diamniotic twin pregnancy occurs when cleavage takes place between 4-8 days post-fertilization. Dichorionic monoamniotic twin pregnancy Dichorionic monoamniotic twin pregnancy is not possible. Monochorionic monoamniotic twin pregnancy Monochorionic monoamniotic twin pregnancy occurs when cleavage takes place between 8-12 days post-fertilization Monochorionic monoamniotic conjoined twin pregnancy Monochorionic monoamniotic conjoined twin pregnancy occurs when cleavage takes place > 13 days post-fertilization. While dizygotic twins always form from 2 separately fertilized eggs, monozygotic twins form from 1 fertilized egg that later splits into 2 zygotes during early pregnancy. The time post-fertilization by which the fertilized egg cleaves is important for determining the number of chorions and amnions. <br>0-4 days: Dichorionic diamniotic twin pregnancy <br>4-8 days: Monochorionic diamniotic twin pregnancy <br>8-12 days: Monochorionic monoamniotic twin pregnancy <br> > 13 days: Monochorionic monoamniotic conjoined twin pregnancy<br/> '''Educational Objective:''' Monochorionic diamniotic twin pregnancy occurs when the fertilized egg cleaves at 4-8 days post-fertilization.<br/> '''References:''' First Aid 2014 page 555 Physiology A pregnant 28-year-old female presents to her gynecologist's office for a routine pregnancy visit. In the office, the gynecologist performs a pregnancy ultrasound. He informs the patient that she has twins. Then he explains to the patient that the cleavage of the fertilized egg likely occurred between day 4 and day 8 post-fertilization. Which of the following ultrasound findings is most likely present in this patient? B Reproductive 2020-10-28T00:12:47Z 2459150.5088773 WBR0333