Twins are two offspring produced by the same pregnancy. In contrast, a fetus that develops alone in the womb is called a singleton , and the general term for one offspring of a multiple birth is multiple. The Yoruba peoples have the highest rate of twinning in the world, at 45—50 twin sets or 90— twins per 1, live births,    possibly because of high consumption of a specific type of yam containing a natural phytoestrogen which may stimulate the ovaries to release an egg from each side. In Central Africa , there are 18—30 twin sets or 36—60 twins per 1, live births. North America and Europe have intermediate rates of 9 to 16 twin sets per 1, live births.
The scientists think knowing about the genetic influences could have applications in reproductive health. Female reproductive system explained Menstruation and ovulation Menopause Fertility, pregnancy and childbirth Breast Fallopian tubes and ovaries Uterus and cervix Pelvis, vagina and vulva Reproductive and contraception Female reproductive system explained Androgen deficiency in women Androgen deficiency in women and its treatment is controversial, and more research is needed Spotting signs of serious illness Reflux in babies How to take a baby's temperature Reducing the risk of SIDS Treating a high temperature Sleep problems in children Coughs, colds and ear infections Diarrhoea and vomiting Infectious illnesses Children's medicines Looking after a sick child Serious conditions and special needs Constipation in young children Your baby's height and weight Baby health and development reviews Leg and foot problems in children. The information contained on this Web site should not be used as a substitute for the medical care and advice of your pediatrician. There have even been instances of fraternal twins Lust of a stepdad different fathers. These babies will be no more alike than siblings born Fraternal twins info and help separate times. Yes No. Those who consumed dairy were five times more likely to have twins.
Bronze babe. Twins – and more
Because fraternal, or dizygotic, twins are 2 separate fertilized eggs, they usually develop 2 separate amniotic sacs, placentas, and supporting structures.
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- Twins are two offspring produced by the same pregnancy.
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- There are generally two types of twins: fraternal and identical.
Madeline K. Fraternal twins come from two separate eggs, unlike identical twins. Fraternal twins tend to run in families, and scientists think they've identified genetic variations at play.
Understanding that might someday help predict who is more likely to have a risky pregnancy, and might also help treat fertility problems. A team led by Dorret Boomsma at Vrije University in Amsterdam studied the DNA of 1, mothers who had given birth to fraternal twins, as well as 12, people who had no history of twins in their families.
They found that the mothers who had variations in two genes, FSHB and SMAD3 , were 29 percent more likely to give birth to twins than mothers without those changes.
This study, which was published Thursday in American Journal of Human Genetics, is the first twin study to rapidly scan the DNA of people looking for key markers, using a technique called genome-wide association study. The researchers were looking for common genetic variations that are associated with giving birth to twins. One prime target was FSHB. It's a gene that prompts production of follicle-stimulating hormone , which helps ovaries produce eggs and is tested to evaluate fertility.
The researchers found that women who had altered regulation of the FSHB gene had higher levels of follicle-stimulating hormone in their blood. Those women would be more likely to produce two separate eggs at once, resulting in fraternal twins.
The other gene, SMAD3 , plays a smaller role in twinning, but does help the body respond to follicle-stimulating hormone. The scientists think knowing about the genetic influences could have applications in reproductive health. Multiple births are riskier for both the mother and children. Developing genetic tests based on these variations could give a better idea of which women may be more likely to have multiple births. And it also might someday help improve fertility treatment.
Women who undergo fertility treatment often use hormones to stimulate the ovaries and produce more eggs at once. As it stands now, there is no good way to gauge how much medication a particular woman may need. This can occasionally lead to ovarian hyperstimulation syndrome. The authors hope that they can someday use their findings to design a genetic test that could identify women who are at risk for severe responses to hormone therapy. This tool might be used to help doctors determine appropriate dosage of hormone treatment.
The initial version of this post said incorrectly that the twin study was published in Journal of Human Genetics, when it was, in fact, published in American Journal of Human Genetics. Accessibility links Skip to main content Keyboard shortcuts for audio player. Don't Tell Me! NPR Shop. Knowing this might help develop safer fertility treatments. Public Health. Facebook Twitter Flipboard Email. April 28, PM ET.
Enlarge this image. Correction April 28, The initial version of this post said incorrectly that the twin study was published in Journal of Human Genetics, when it was, in fact, published in American Journal of Human Genetics.
Monoamnionic twins divide after the first week. Sometimes one twin fetus will fail to develop completely and continue to cause problems for its surviving twin. Updated Complementary and alternative care. Polycystic ovarian syndrome PCOS Polycystic ovarian syndrome is a hormonal condition associated with irregular menstrual cycles, excess hair growth, acne, reduced fertility, and increased risk of diabetes and mood changes Intrapartum death, which is more common, occurs when a baby dies while the mother is giving birth. Alternately, fraternal twins can appear completely different to each other right from birth, with different hair colouring, facial features, sizes and birth weights.
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Fraternal twins are correctly described as dizygotic, the result of multiple egg-sperm combinations. Their genetic similarities are the same as any siblings. They may share a family resemblance, or they may look totally different. There are many reasons why it's important to determine twin type, but it's not always an obvious determination.
Sometimes, asking a few simple questions can help parents evaluate their twins' zygosity and come to a conclusion as to whether they are identical or fraternal.
While some twins can be identified immediately, others may not be determined for months or years. Zygosity can be determined through blood testing, placental analysis or with an at-home DNA testing kit. It's nice to have an answer to the endless questions about twin type.
But more importantly, the answer could have implications for medical situations. Ultrasound or placental analysis is often inconclusive. While a doctor can make an assessment during pregnancy, many wrongly conclude that babies are fraternal simply because there are two placentas.
Follow up with DNA testing after the babies are born if you want to know for sure. If your answers to the above questions are inconclusive, the only way to determine zygosity is with DNA testing.
If it's important for you to know, order a kit, follow the directions, and send in a sample for analysis. If you can't afford to purchase a DNA test kit, you may be able to get tested for free by participating in a research study.
Or contact a "parents of multiples" organization such as Multiples of America or local research university. Get diet and wellness tips to help your kids stay healthy and happy. American Pregnancy Association. Are My Twins Identical or Fraternal? Monozygotic twins of opposite sex. Cytogenet Cell Genet. Embryo transfer practices and multiple births resulting from assisted reproductive technology: an opportunity for prevention. Fertil Steril.
Twin Res Hum Genet. National Organization for Rare Disorders. Twin-Twin Transfusion Syndrome. Updated American College of Obstetricians and Gynecologists. Multiple Pregnancy. Updated January More in Ages and Stages. Are the twins males, females, or one of each? All babies possess either XX or XY chromosomes that distinguish whether they are girls or boys, respectively.
A boy has XY chromosomes and a girl has XX chromosomes. The occurrence of girl-boy twins happens when one X egg is fertilized with an X sperm and the other X egg is fertilized with a Y sperm. Monozygotic twins are always the same gender, except in rare cases. Do the twins have the same blood type? Knowing your multiples' blood type can help determine zygosity.
Monozygotic identical twins will have the same blood type, with a few very rare exceptions. Complementary and alternative care. Healthy living Healthy living. Babies and toddlers Children Drugs and addictive behaviours. Environmental health. Family Violence.
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Service profiles. Blog Blog. Blog authors. Podcast Podcast. Back to Reproductive system - female Home Conditions and treatments Reproductive system - female Twins - identical and fraternal. Twins - identical and fraternal Share show more. Listen show more. More show more. Tags: Reproductive system - female Reproductive system - female - Fertility, pregnancy and childbirth. 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. The average cycle is around 28 days. After a menstrual period, rising levels of the hormone oestrogen help to thicken the lining of the womb the endometrium and release an egg from one of the ovaries ovulation.
If the egg is fertilised on its journey down the fallopian tube, it lodges in the thickened womb lining, starts dividing and evolves into an embryo. This occurs because the fertilised egg divides in two while it is still a tiny collection of cells. The self-contained halves then develop into two babies, with exactly the same genetic information.
The biological mechanisms that prompt the single fertilised egg to split in two remain a mystery. Approximately one quarter of identical twins are mirror images of each other, which means the right side of one child matches the left side of their twin. These babies will be no more alike than siblings born at separate times.
The babies can be either the same sex or different sexes, with the odds roughly equal for each. It is proposed that the egg splits in two, and each half is then fertilised by a different sperm. This theory is an attempt to explain why some fraternal twins look identical.
Gestation for twins The normal length of gestation for a single baby is around 40 weeks. However, gestation for twins, either identical or fraternal, is usually around 38 weeks. Since twins are usually premature, they are more likely to have lower birth weights.
Prematurity is associated with increased risk of a number of disorders, including jaundice. Giving birth to twins Childbirth can give rise to complications when just one baby is present, so twins present extra potential for difficulties. It is advised that women carrying twins give birth in hospital, rather than at home. The babies can be delivered vaginally, but caesarean section delivery may be considered a better alternative in some circumstances. Zygosity testing It is difficult to tell if twins are identical or fraternal at birth.
Some identical twins may be born with individual sets of membranes, which may lead to the mistaken assumption that the babies are fraternal. One way to tell the difference is to have the twins DNA-tested.
Identical twins share the same genetic information, while fraternal twins share around half. The test can be done with a sample of cheek cells, collected painlessly. Other tests include blood group examinations. Where to get help Your doctor Paediatrician Maternity hospital Things to remember Twins account for over 90 per cent of multiple births. To form identical or monozygotic twins, one fertilised egg ovum splits and develops into two babies with exactly the same genetic information. To form fraternal or dizygotic twins, two eggs ova are fertilised by two sperm and produce two genetically unique children.
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Fraternal twins & identical twins | Raising Children Network
The chances of being born a twin are about 3 in The chances of being born an identical twin are about 1 in When more than one baby is born twins or more , this is called a multiple say mul-ti-pul birth.
A few years ago more multiple births were happening because some women who were having problems getting pregnant were able to have a special treatment called fertility treatment. This sometimes led to more than one baby. Nowadays the treatment has changed so that usually only one baby is born. Three babies together are called triplets, 4 are called quadruplets quads , and 5 are quintuplets quins. Identical twins happen when a single sperm from the father fertilizes a single egg from the mother.
Non-identical twins are sometimes called fraternal twins. Fra-ter-nal means brother. There are also, in very, very rare cases, conjoined or 'Siamese' twins. These are babies who are joined together and may share some parts of their bodies. Their heads may be joined together, or a different body part is joined. Having another person who is the same age as you can be really great! You always have someone the same age to play with. But that doesn't mean that you are always going to be the best of friends.
Just like other siblings you may have some good times and some bad times. If you are identical you might have a lot of fun confusing others who can't tell you apart but it can be annoying to be called your twin's name all the time. People might assume because you are identical to look at then you are identical in other ways.
It can be hard to be an individual! It can be annoying if one of you is really good at something and the other one isn't. What if you are not really good at sport and the other one is?
The same thing might apply to maths or English, music or anything else. Write in on the feedback button if you have something to share about being a twin or a triplet and we'll add your comments to this topic. Being a twin can be really interesting to people who are doing research about health and behaviour. It might be possible to tell if some diseases happen more often if you have exactly the same genes. Some identical twins have reported sensing when their twin has been hurt or feels sad.
Some have even talked about feeling the pain for their twin even when they themselves were not hurt or sick.
Don't think I'd like that! There are a few stories of twins who have been adopted by different families at birth and who have never seen each other until many years later.
When they have met they have discovered all sorts of similarities in their lives. They are a boy and a girl. They do look like each other". Even though the boys were fraternal I couldn't tell the two boys apart when I was looking at them from the back. We've provided this information to help you to understand important things about staying healthy and happy.
However, if you feel sick or unhappy, it is important to tell your mum or dad, a teacher or another grown-up. Twins — and more identical; triplets; sperm; egg; uterus; pregnant; baby; twins; multiple; Contents Chances of being a twin Identical twins Non-identical twins 'Siamese' twins Being a twin Dr Kate says Some famous twins Chances of being a twin The chances of being born a twin are about 3 in Identical twins Identical twins happen when a single sperm from the father fertilizes a single egg from the mother.
Soon afterwards this fertilized egg divides into two and starts forming two babies. They will have identical genes. They are the same sex. Some identical twins will share the same placenta where they get the nutrients needed to grow and the same sac, a kind of bag for the baby inside the mother's womb or uterus. Some identical twins will have their own placenta and sac inside the mother's uterus. Some identical twins may be different sizes when they are born but they usually are about the same size when they are 6 months old.
Identical twins may not start off looking identical but they grow more alike as they get older and it can be hard for others to work out who's who. Non-identical twins Non-identical twins are sometimes called fraternal twins. Fraternal twins can be both boys, both girls, or one of each. They are formed when 2 sperm fertilise 2 eggs. Each has its own place in the uterus. Each has a placenta and sac. These twins often look very alike at birth but may grow less alike as they get older, just like other kids in the family.
These twins come from the same egg but it hasn't divided properly. They are always the same sex. Being a twin Having another person who is the same age as you can be really great!
Dr Kate says Being a twin can be really interesting to people who are doing research about health and behaviour. One likes music, the other sport People say, "Twins you poor things" But I don't care I like being a twin Nick "I have friends who are twins - they look a bit alike but are not exactly the same. Related Topics Sexual reproduction - how babies are made - for kids Genes - not the kind you wear! Last updated: Monday 14 November