After birth, if one member of a pair of MZ twins had a sex change operation, that would also result in a pair of opposite sex MZ twins. Machin G. Non-identical monozygotic twins, intermediate twin types, zygosity testing, and the non-random nature of monozygotic twinning: A review. Zech, N. References: Machin G. I am a twin. Do I have an increased chance of having twins?
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The State of Victoria and the Department of Health shall not bear any liability for reliance by any user on the materials contained on this website. Skip to main content. Reproductive system - female. Home Reproductive system - female. Twins - identical and fraternal. Actions for this page Listen Print. On this page. Multiple births are more common than they were in the past, due to the advancing average age of mothers and the associated rise in assisted reproductive techniques, in particular the use of fertility drugs.
Twins account for over 90 per cent of multiple births. There are two types of twins — identical monozygotic and fraternal dizygotic. To form identical twins, one fertilised egg ovum splits and develops two babies with exactly the same genetic information. This differs from fraternal twins, where two eggs ova are fertilised by two sperm and produce two genetically unique children, who are no more alike than individual siblings born at different times.
Twins are more or less equally likely to be female or male. Factors that increase the odds of having twins Some women are more likely than others to give birth to twins. The factors that increase the odds include: Advancing age of the mother — women in their 30s and 40s have higher levels of the sex hormone oestrogen than younger women, which means that their ovaries are stimulated to produce more than one egg at a time. Number of previous pregnancies — the greater the number of pregnancies a woman has already had, the higher her odds of conceiving twins.
Heredity — a woman is more likely to conceive fraternal twins if she is a fraternal twin, has already had fraternal twins, or has siblings who are fraternal twins. Race — Black African women have the highest incidence of twins, while Asian women have the lowest. Assisted reproductive techniques — many procedures rely on stimulating the ovaries with fertility drugs to produce eggs and, often, several eggs are released per ovulation.
Fertilisation Hormones secreted by the ovaries, and a small gland in the brain called the pituitary, control the menstrual cycle. This twin will be assigned female at birth but may have developmental issues, as well as difficulties with fertility later in life, according to the National Health Service.
Once a person becomes pregnant, their body stops releasing new eggs for potential fertilization — except in some rare cases.
A phenomenon known as superfetation can occur when a second egg gets released and fertilized after a person is already pregnant. In this case, both fertilized eggs will develop, but one twin will be slightly older than the other. This is known as heteropaternal superfecundation — a common occurrence in animals but very rare in people. Twin pregnancies often come with an increased risk of developing some medical conditions.
These can include:. A twin pregnancy has risks of complications, so parents should make sure to receive good prenatal care and seek medical attention for any concerns. Identical twins are the same in so many ways, but does that include having the same fingerprints? There's conflicting information out there so we look….
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A fetal arrhythmia is an irregular heart rate — too fast, too slow, or otherwise outside the norm. It's often benign. Postpartum diarrhea after a C-section is normal. Health Conditions Discover Plan Connect. Identical Nonidentical Third type Unique identical twins Unique fraternal twins Risks Takeaway You may be familiar with the most common types of twins — fraternal and identical — but several other rare subtypes exist too. Identical twins. Nonidentical twins. Is there a third type?
Unique identical twins. Unique fraternal twins. Medical risks during a twin pregnancy. The takeaway.
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