The Different Types Of Twin Pregnancies

Twins can be the same (identical-monozygotic) orincreases. To put it in perspective, your chance of
different (fraternal-dizygotic). Fraternal twins, triplets, orgiving birth to twins if you are less than 25 years of
more develop when two or more eggs are fertilizedage is less than half of what it would be after the age
by separate sperm. Fraternal fetuses have separateof 35.
placentas and amniotic sacs (the bag containing the2. You are more likely to conceive twins in the first
fluid around a baby).few menstrual cycles after stopping birth control pills.
Identical twins come from a single egg that has been3. Infertility treatment. Fertility drugs stimulate your
fertilized by one sperm. For unknown reasons, theovaries to release multiple eggs, which can be fertilized
fertilized egg splits into two or more embryos duringat once. This may result in a multiple pregnancy. You
the first stage of development. Some identical twinsare, therefore, more likely to have a multiple pregnancy
share the same placenta. However, they usually growif you use fertility drugs or assisted reproductive
within separate amniotic sacs in the uterus. In raretechnology (ART - In Vitro Fertilization IVF).
cases, identical twins share one amniotic sac4. ART is the transfer of embryos directly into the
(monoamniotic).uterus. In the early days, when success rates were
Fraternal multiples:extremely low, several embryos were transferred in
1. Can be of different sexes and may have differentthe hope of achieving a pregnancy. Nowadays, 25%
blood types.to 30% of pregnancies from ART are twins; 5% are
2. They may look very different from one another,triplets and less than 1% are quadruplets or more. As
with different-coloured hair and eyes. They may alsotechniques have improved, success rates from IVF
look alike, as siblings often do.embryo transfer have increased and reasonable
3. Tend to run in families.success rates are being achieved with single embryo
4. They are more common in older mothers, Africantransfer and this reduces the incidence of multiple
races and when there is a family history of twins.pregnancies.
They are least common in Asian families. If you haveWhat is the prevalence of multiple pregnancy?
already carried fraternal twins, you have double theThe natural incidence of twins is 1 in 80 pregnancies
usual risk of having twins. A history on your partner'sand for triplets 1 in 8000 pregnancies. The incidence is
side of the family does not increase your risk ofrising as a result of IVF and a tendency for women to
multiple pregnancy.deliver later in their reproductive years. Naturally
Identical twinsoccurring quadruplet births occur in 1 per 600,000 births.
1. Are always the same sex and blood type.The UK would, therefore, expect one set of naturally
2. They do not necessarily look exactly alike. One mayoccurring quadruplets each year. There are estimated
be right-handed while the other is left-handed.to be approximately 125 million human twins and triplets
3. They develop at random. They are not related toin the world, and just 10 million identical twins.
maternal age, race, or family history of twins.One in two pregnancies with same sex babies are
4. Multiples that are conceived with infertility treatmentmonozygous (identical twins). The rate of identical
are usually fraternal, rather than identical.twins remains at about 1 in 333 pregnancies across
What are the causes of multiple pregnancy?the globe.
1. With increasing maternal age the chance of twins