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