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There are two types of twins, identical twins and non-identical twins. In identical twins, babies come from one egg fertilized by one sperm cell. This fertilized egg will then divide into two or more to produce two fetuses that have the same DNA, blood type, and physical characteristics such as skin color, hair color, and eye color. The gender is usually the same and the faces are very similar. Identical twins also usually share the same placenta but grow in different amniotic sacs.
However, twins are not identical (or so called fraternal twins) grows from two eggs and two different sperm cells, does not share a placenta or amniotic sac, and usually does not resemble identical twins. Blood type and gender can be the same or different.
How does one get twins?
No one knows exactly why a pregnancy can produce twins, especially for identical twins. In fact, all pregnant women have the same chance of having identical twins. There may be 1 identical twin pregnancy out of 350-400 pregnancies. Usually, identical twins are not inherited in the family, nor are they influenced by age, ethnicity or age.
However, non-identical twins are more common when compared to identical twins. Several factors that can influence the occurrence of non-identical twins include:
- Ethnicity: non-identical twins are usually more common in certain ethnicities. The incidence of non-identical twins was mostly experienced by African ethnicities, while the least occurred in ethnic Japanese. In parts of western Europe, multiple pregnancies occur in 1 in every 60 pregnancies, while in Nigeria twins occur in 1 in 20-30 pregnancies. But even so, Nigerians living outside the country then experience a reduced chance of giving birth to twins, so that the high chance of having twins for African ethnicity is suspected more due to diet and environmental factors.
- Age: although giving birth at the age of old has its own risks, but it turns out that if you are pregnant over the age of 35, you are more likely to have twins. This is because if you are older, you tend to release more than one egg during ovulation.
- Heredity: non-identical twins can be inherited from the mother. Non-identical twins are caused by the presence of two eggs, a woman's ability to produce more than one egg at ovulation tends to be passed on to women. So if the mother-to-be has a mother or grandmother who is also non-identical twins, then the possibility of producing twins is also greater.
- The number of children before: although it has not been scientifically proven, but if you have had children several times, then the chances of you getting twins are also greater. This is because it means that your reproductive system is working properly and there are no problems with ovulation, so the chances of producing more than one egg at ovulation are greater. Or, if you have previously given birth to twins, then it is not impossible that the next pregnancy is also twins.
- IVF: in vitro fertilization, or often referred to as the IVF method, is a technique used to help those diagnosed with infertility or problems with the reproductive system to have children. During the IVF procedure, eggs are taken from the ovaries and fertilized by sperm, this whole process is carried out in the laboratory. After that the fertilized egg, or called an embryo, will be implanted back into the uterus and then allowed to grow and develop like a fetus in general. When undergoing IVF, usually more than one embryo will be implanted in the uterus to increase the chances of the program being successful, but it may be after that more than one embryo will develop into a fetus. This is what causes multiple pregnancies in those undergoing the IVF program. According to the NHS Choices, conception normally results in 1 twin pregnancy out of 80 pregnancies. But with IVF, the chance of multiple pregnancies is 1 in 5.
