Fraternal and Identical Twins

Topics: Twin, Pregnancy, Zygote Pages: 3 (1144 words) Published: December 23, 2013
FRATERNAL AND IDENTICAL TWINS 2 Fraternal and Identical Twins
Not all twins act the same, even the ones that are identical. They may come about the same way. Fraternal and Identical Twins have some of the same traits but are definitely not the same. All twins, whether fraternal or identical, are truly two separate unique individuals.

There are four different types of twins. The first is fraternal twins that either never divided or divides within the first four days and have two separate amniotic sacs and placentas. This is included for almost all fraternal twins. The second is Identical twins that share the same placenta, but have two amniotic sacs. This occurs when the embryo splits in 4-8 days and is most likely to occur in 60-70% of all identical twin pregnancies. The third is also identical twins that share the same amniotic sac and appear when the embryo splits after 9 days. The last and most uncommon type of twins are the conjoined twins, which occurs when division takes place later than 12 days after fertilization. This can cause the embryo’s to become joined together on some part of their body. Identical Twins are most unique. They are the most admired and sometimes the most notable. It is believed by most that this is the most common type of twin. This is not a proven fact because fraternal twins have become the norm, while identical twins have become somewhat of rarity. There are 3 different ways that identical twins can develop and be carried: The first case is where there is only one placenta that feeds the babies, but there can be two amniotic sacs. When there is 1 placenta and 2 amniotic sacs then the pregnancy is referred to as having an identical pregnancy. Twins may also occur from invitrofertilization. This is when several

FRATERNAL AND IDENTICAL TWINS 3 fertilized eggs are...
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