A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Types of Twin Pregnancy

"Half Identical" Twins: Polar Body Twins
"Half Identical" Twins: Polar Body Twins

Twin births are common, though there are rare cases of unique twins. Explore instances of polar body twins, parasitic twins, and mirror images twins. Explore instances of polar body twins, parasitic twins, and mirror images twins.

Boy/Girl Identical (Monozygotic) Twins
Boy/Girl Identical (Monozygotic) Twins

*The rare instance in which a set of boy/girl monozygotic/identical twins occurs is the result of Turner's Syndrome, in which both individuals are actually XY boys, but one child loses the Y chromosome, yielding a baby who is XO.

Conjoined Twins
Conjoined Twins

Fraternal twins — the most common kind of twins — occur when two separate eggs are fertilized by two different sperm. Each twin has his or her own placenta and amniotic sac. The twins can be two girls, two boys, or a boy and a girl. Identical twins occur when a single fertilized egg splits and develops into two fetuses.

Fraternal Twins
Fraternal Twins

Fraternal twins — the most common kind of twins — occur when two separate eggs are fertilized by two different sperm. Each twin has his or her own placenta and amniotic sac. The twins can be two girls, two boys, or a boy and a girl. Identical twins occur when a single fertilized egg splits and develops into two fetuses.

Half-Identical Twins
Half-Identical Twins

The twins first came to Parisi's attention when their parents brought one of them to the University of Washington for unrelated testing. In the course of evaluating the test results, doctors realized that the twins had developed from the same egg, just as identical twins do – but from different sperm, like fraternal twins.

Identical Twins
Identical Twins

Identical twins occur when a single fertilized egg splits and develops into two fetuses. Identical twins might share a placenta and an amniotic sac or the twins might share a placenta and each have separate amniotic sacs.

Mirror Image Twins
Mirror Image Twins

Mirror twins—or mirror image twins—aren’t really a category of twins, like identical/monozygotic twins. Rather, the term “mirror twins” describes a characteristic of some twins, where their features appear asymmetrically -- that is, on opposite sides. A birthmark may manifest on the left side of one twin but on the right side of the other.

Mixed Chromosome Twins
Mixed Chromosome Twins

There are 7 different kinds of twins, categorized as: Identical, Fraternal, Half-Identical, Mirror Image Twins, Mixed Chromosome Twins, Superfecundation and Superfetation. pixabay Normally, except the first two kinds, others are known to be quite rare to occur.

Parasitic Twins
Parasitic Twins

Parasitic Twin and Vanishing Twin Syndrome Parasitic or Heteropagus Twins are asymmetric conjoined identical or monozygotic twins in which the tissues of a severely defective twin (the parasite) are dependent on the cardiovascular system of the other, largely intact twin (autosite) for survival.

source: babymed.com
Superfecundation
Superfecundation

Superfecundation is when there are twins from ovulation on the same day with two separate fathers. Superfetation happens if there is a second pregnancy from two separate ovulations; the second ovulation can occur weeks or even months after the first.

source: babymed.com
Triplets and 'Higher Order Multiples' (HOMs)
Triplets and 'Higher Order Multiples' (HOMs)

Higher Order Multiples – Triplets, Quadruplets and More ... is a twin, triplet, ... of becoming pregnant with higher order multiples

image: cbs.nl
Twins Conceived Separately: Superfetation
Twins Conceived Separately: Superfetation

Superfetation differs from the conception of typical twins, where multiple ova are released in a single cycle. This can happen naturally or be stimulated with fertility drugs. When more than one ovum is fertilized and implants in the uterus, the result is dizygotic (fraternal) twins, triplets, or other multiples.

image: snipview.com
Twins With Different Fathers: Heteropaternal Superfecundation
Twins With Different Fathers: Heteropaternal Superfecundation

That is, each egg can be fertilized by a different father. However, if you know twins who look nothing alike, don't assume that they have separate fathers. Like any siblings, twins who have the same father can look completely different from each other. They may even appear to be of different races.

Related Types