Some twins are identical, some are not, and then there’s the pair that is identical but are a different sex. Confused? Well, we are here to clear the confusion once and for all. Before we proceed, let’s talk about the few common twin pairs that we usually come across: 

• Identical Twins (twins with almost similar features)
• Fraternal Twins (twins with different or same sex but completely different features)
• Mirror Image Twins (not really a category of twins but a term used describe the features of twins, which are almost unrecognizable)

Now that you know the basics, have a look at a few frequently asked questions about mirror image twins:

Can Mirror Twins Be Different Genders?

If you have a twin, do people often come up to you and ask, “Are you identical or fraternal twins?” If you are a girl and your twin is a boy, then the answer is clear, but if both of you are either males or females, then one automatically assumes that you two are identical.

In order to understand how mirror twins are formed, you need to know about zygosity. This term explains how a zygote is formed with the union of a male gamete (germ cell) and a female gamete during the process of sexual reproduction. In simpler terms — zygosity describes the origin of the twins.

This is where they are wrong! Keeping in mind the combination of zygotes, mirror twins can only be identical, as in boy-boy or girl-girl. This is because they are monozygotic.

Can Mirror Twins Be Identical?

It seems that most of the questions surround this one dilemma. As explained earlier, the extent of similarities depend on the zygote. Since we are talking about identical twins, which always have the same sex, then the answer is a little complicated. 

Not to confuse you, but the answer to this question is yes and no. We have already established that identical twins are monozygotic. The reason why identical twins are also called mirror twins is because they are a reflection of each other. This is where the similarities end. If you look closely, you will find small differences in their physical characteristics, which include:

• Moles
• Birthmarks
• Freckles
• Eye shape
• Dimples
• Eyebrow shape
• Ear shape
• Nostril shape
• Hair whorls
• Cowlicks
• Teeth

These physical characteristic might be on the right side of one twin and on the left on the other twin. This is perhaps one of the top features that differentiate mirror twins from one another.

What Causes Mirror Image Twins?

Think of mirror twins as nature’s copy-paste. This doesn’t mean that there’s no scientific backing behind their formation. Between the 4^th and 8^th day of a normal fertilization process, 1 fertilized egg splits into 2 identical embryos. These two embryos form into two babies.

However, in the case of mirror twins, the egg splits between the 9^th and 12^th days, which cause the similarities. Since the fertilized egg was divided, the embryos develop similar features 

How Are Mirror Twins Formed?

Going into more detail, the formation of twins is quite different. 1 egg is fertilized by 1 sperm and as a result, a single zygote forms. The pregnancy proceeds naturally with the embryo growing for 2 weeks after conception. Then, the embryo splits and forms two identical parts. Now, the womb has two embryos and the twins have the same sex, and 100% of their genes match. There are only 25% chances that identical twins turn out to be mirror twins.

How Many Mirror Twins Are There in the World? 

There’s no information available online on how many twins are there in the world. However, it is estimated that out of every 1,000 people, 32 are twins. It’s not known whether this estimated population comes out as mirror twins or fraternal twins.

Are Mirror Twins the Same as Identical Twins? 

This is the one question that confuses people whenever the topic about twins is brought up. As explained earlier, mirror twins is a term given to the characteristics that describe identical twins. Identical twins are monozygotic, so when it comes to differentiating mirror twins, you will have to look for the subtle changes in them. For example, one twin might be left-handed and the other right-handed.

Identical twins are born when the egg splits between the 2^nd and 8^th day, whereas mirror twins are born when the egg splits between 9^th and 12^th day. Identical twins will have a few visible physical differences but mirror twins are carbon copies of themselves. In some case, mirror twins are also mentally connected in way that if one has a headache, the other experiences it too.

When the egg splits after the 12^th day, the twins born are called conjoined twins. These types of twins are bonded to each other physically. They might share a limb or a vital organ.

In a nutshell — yes, mirror twins and identical twins are the same.You can also say that all identical twins are not born mirror twins, but all mirror twins are known as identical twins.

Are Mirror Twins Organs Reversed?

Yes, but not the vitals ones. The spleen in one twin might be on the opposite side and vice versa. However, when it comes to the heart, the appendix and other such vital organs, the mirroring is quite rare.

Are the Property Brothers Mirror Twins?

A little background — The Property Brothers is a Canadian TV show in which two brothers Drew Scott and Jonathan Scott who are identical twins buy neglected houses and then renovate them.

Fun Fact: Jonathan was the first to be born and as the doctor was finishing up, he realizes that there was another baby. To the mother, this was a complete surprise because she wasn’t expecting twins. 

Most people consider the Scott brothers to be fraternal twins because they look quite different. Even their mom had a hard time coming to terms that they are identical and fraternal. Fans can easily set them apart because their physical features are different. As we have learned, mirror twins tend to be mirror images of themselves, which is why we can safely say that the Scott brothers are not mirror twins.

Are the Olsen Twins Mirror Twins?

We all know the Olsen twins from the hit TV sitcom Full House. It was one of the top-rated shows in the late 1980s. Most of the audience watching the show sitting at home had no idea that Michelle had a twin. It wasn’t until the episode where we see two Michelle; we realized there’s a possibility that this was no video graphic manipulation. 

Yes, the Olsen twins look exactly the same but they are not mirror twins. In an interview, the Olsen twins revealed that a doctor told them they were sororal twins (fraternal twins with same sex). They definitely have different physical characteristic such as Mary Kate is taller than Ashley and Ashley is right-handed, whereas Mary Kate is left-handed.

Is There Any Relation Between Mirror Twins and Left Handedness?

Studies have been conducted in depth on twins to find out how their brain development affects their activities. There has been a long standing debate on whetherthere’s any relation between mirror twins and their hand preference. To make it clear for you, most of the twins are left handed. 

In fact, according to Washington State Twin Registry, in about 21% of monozygotic twins, one twin in a pair is left handed and the other is right handed. If we talk about the general population, only 10% of the people are left handed. However, when it comes to twins, about 17% of them are left handed. 

The left hand preference is not due to any genetic changes. A study published in the Frontiers of Psychology journal conducted a study on twins to find out their hand preference and cognitive differences. The researchers weren’t able to come to a conclusion due to lack of research data, especially because of zygotic discernibility. However, the results did reveal that most mirror twins prefer their left hand. They chalked up the weak results to fewer participants.

Environmental factors might have a hand in the hand preference, which include rising hormone levels in the mother, stress during birth and position of the twins in the womb. If the twins born are mirror twins, then there’s a high chance that one of them will be left handed. Researchers weren’t even able to determine the preference of left hand in a study that had 4,000 twin participants. This brings us to the conclusion that it’s not the sample, the environment or genetics that cause this phenomenon but a combination of these three and something else. 

What we have learned here is that mirror twins are actually identical twins but the same cannot be said when the positions are reversed. People might look exactly alike and not be mirror twins, as is the case of Olsen twins.Mirror twins might be the mirror image of each other but they don’t have the same fingerprint. Only genetics can determine what kind of twins a pair is and nothing else.

Pregnancy diet, exercise & prenatal vitamins

Do what’s possible to make yourself feel good. Go to a spa, get a massage, relax and keep your feet up. Do any kind of exercise you like – as long as you don’t engage in contact sports or horse riding. You still need to take an iron supplement at 31 weeks pregnant with twins.

Pregnancy symptoms & belly pictures

Your babies are getting bigger and that takes a toll on your body. There’s no doubt that it’s hard work carrying two children. Common pregnancy symptoms are:

• You feel exhausted. You may also feel misrable or unwell.

• You may feel like there’s not enough room in your abdomen. Your babies are pressing on your diaphragm, liver, stomach, intestines and bladder.

• You might feel sore – like when you have a bruise. That’s often caused by your babies kicking in the same place again and again. They may have a favorite position.

• Your lower back and pelvis might be tender or sore. It’s common to have muscle tension in your buttocks, abdomen and pelvis.

• Some women feel abdominal pressure. As your twins grow and become heavier, it puts increasing pressure on the muscles in your pelvic floor. If you feel intense and sudden pressure, you should be aware that it can be early signs of labor.

Baby weight & fetal development

Your babies measure approximately 41 centimeters (16.14 inches), when you’re 31 weeks pregnant with twins. The median weight for dichorionic twins is 1730 grams (3lbs, 13oz) and for monochorionic twins it’s 1642 grams (3lbs, 9oz). Look at our estimated fetal weight charts to learn more about how twins grow in the second half of pregnancy. Your children are developing their senses. They can now distinguish light from dark, feel, hear and taste what you’re tasting. The flavors your babies taste inside the womb won’t be quite as strong or distinct as those you taste. Sensory impressions are sent to their brains, stimulating their brain development.

Twin boys & genital abnormality

If you are expecting a boy – or two – their testicles will start to descend into the scrotum a few weeks before birth. When you’ve given birth, the midwife or doctor will check to make sure that their testicles are in the right place, as a part of a newborn’s physical examination. Cryptorchidism – known as undescended testicles – is the most common genital abnormality in boys.

How common is undescended testicles?

Undescended testicles affect about 3-4 percent of baby boys born at term. If your twins are born preterm, there’s a greater risk that one or both of the testicles haven’t descended. Often, the undescended testicles will descend on their own within the first sixth month after birth. If not, they can be helped in place with a minor operation. The operation is important as the condition can affect fertility later or lead to other medical problems.

Previous week – 30 weeks pregnant with twins

Next week – 32 weeks pregnant with twins

Pregnancy diet, nutrition & prenatal vitamins

If you feel like you don’t have enough room in your belly for food, eat small meals many times a day. Try to switch to a low-acid diet. Especially avoid greasy and fatty foods, alcohol, chocolate, sugar, coffee and tea. Chamomile tea is the exception. Chamomile tea actually helps settle your stomach. Also, remember to take an iron supplement.

Pregnancy symptoms & belly pictures

Common pregnancy symptoms at 30 weeks are:

• Pelvic pressure. It’s heavy to carry twins, and you may feel pain or pressure in your pelvic muscles. Be wary off sudden and intense pelvic pressure, sometimes in combination with braxton hicks contractions. These could be signs that you’re going into early labor.

• Your belly can feel very tight, like you don’t have enough room for food. There are medications you can take if you struggle with indigestion, acid reflux or heart burn. Some women also benefit from making changes to their diet.

• How you feel at 30 weeks pregnant with twins is very dependent on your health, the course of your pregnancy, your weight before you got pregnant and your twin pregnancy weight gain. You may feel very uncomfortable at times. Talk to your doctor or midwife if you are feeling misrable most of the time.

Baby weight & fetal development

Your babies measure approximately 40 centimeters (15.75 inches), when you’re 30 weeks pregnant with twins. The median weight for dichorionic twins is 1537 grams (3lbs, 6oz) and for monochorionic twins it’s 1479 grams (3lbs, 4oz). Look at our estimated fetal weight charts to learn more about how twins grow in the second half of pregnancy. In early pregnancy, the skeletal structures of your babies start out as flexible cartilage. Gradually they begin to ossify, turning into harder bone. However, when your babies are born, their bones will still be much softer compared to the bones of an adult. During your children’s toddler years, they become hard as of an adult. It’s good that your children’s bones are softer. It makes them less likely to break during birth and when they’re learning to walk. Your babies lungs are almost mature at 30 weeks pregnant with twins. Your babies are practicing breathing. This sometimes give them the hiccups – you can feel this as small, rhythmic movements in your stomach.

30 weeks pregnant with twins ultrasound

You should be offered regular ultrasound scans to make sure that your babies are growing as expected. Monochorionic twins are usually seen more often than dichorionic twins. Monochorionic twins are twins that share a placenta. Dichorionic twins have separate placentas. You should also be seen more often if you have a hypertensive disorder or gestational diabetes.

Dichorionic twin girls at 29+3 weeks.

Previous week – 29 weeks pregnant with twins

Next week – 31 weeks pregnant with twins

Pregnancy diet, nutrition & prenatal vitamins

Remember to take an iron supplement. Get more rest than you got before you were pregnant.

Pregnancy symptoms & belly pictures

The more weight you gain, and the bigger your babies get, the more it takes a toll on your back and pelvis. You may feel quite uncomfortable at this point in your pregnancy. It may also affect how well you sleep. Other pregnancy symptoms are:

• Braxton hicks contrations. Your body is preparing for birth. It’s normal and nothing to worry about. However, if you’re worried that you might be going into premature labor, then contact your doctor or midwife. If you feel intense pelvic pressure, if you’re bleeding or spotting or if your contractions become regular, then it’s especially important that you go to the hospital as these symptoms are signs of early labor.

• You may feel less energetic and more tired than usual. This could be caused by hormones, an iron deficiency or if your stomach isn’t working as well as before you got pregnant.

Baby weights & fetal development

Your babies measure approximately 38,5 centimeters (15.16 inches), when you’re 29 weeks pregnant with twins. You’re now in the third trimester of your pregnancy. The median weight for dichorionic twins is 1367 grams (3lbs) and for monochorionic twins it’s 1293 grams (2lbs, 13oz). Look at our estimated fetal weight charts to learn more about how twins grow in the second half of pregnancy. Your babies are surrounded by amniotic fluid which enables them to move more freely. When you’re 29 weeks pregnant with twins, your babies can easily kick, stretch, suck their thumbs, do somersaults forwards and backwards and bend hands and feet.

Ultrasound & fetal movement

Most babies have a consistent pattern of how active they are. You need to react if one baby’s activity level is significantly different than usual. There’s no need to compare them – you don’t have to worry if one of your children in general is less active than the other. That is normal. However, you need to react if one of them is less active than he or she usually is. If you experience that one or both of your children are less active than usual, contact your midwife or doctor and let them know what you’re experiencing. They may want to do an ultrasound scan to make sure that your babies are okay. There are a few things you can try to do on your own to get them to kick or move around:

• Drink a lot of cold water. Your babies will feel a drop in temperature and may react.
• Lie down and keep still. Most babies are active when you relax – this is why some pregnant women experience a lot of activity when they go to bed at night.

Previous week – 28 weeks pregnant with twins

Next week – 30 weeks pregnant with twins

Pregnancy diet, exercise & prenatal vitamins

Remember to take an iron supplement. If you’re bothered by constipation, drink plenty of water and keep active. A brisk walk is fine.

Pregnancy symptoms & belly pictures

Many women pregnant with twins feel uncomfortable – or even miserable – at this point in their pregnancies. This can be caused by pregnancy symptoms like:

• Swelling. According to the American Pregnancy Association (APA) your body produces approximately 50 percent more blood and body fluids during pregnancy. This can cause swelling – also named “edema” – at any time in pregnancy. However, it can particularly be a problem during your last trimester. It’ll help to rest with your legs up high. If that’s not possible consider wearing compression stockings during the day.

• The twin pregnancy weight gain. You’re not only carrying the weight of your babies but also more fluids and a placenta that’s getting heavier. The placenta(s) goes from weighing nothing in early pregnancy to weighing around 1 kilo at birth.

Ultrasound & fetal movement

At this point in your pregnancy, you’ve had the dating and chorionicity ultrasound scan and the anomaly scan between 18 and 20+6 weeks. You’re still being seen regularly to ensure that your twins are growing, developing and moving as expected. Women carrying identical twins who share a placenta – monochorionic twins – are usually seen more often than women expecting dichorionic twins. This is because they are more at risk of twin pregnancy complications due to the shared placenta. The identical twins in the picture below are mo-mo twins. This means that they share both the inner and outer sac and the placenta. Only about 1 percent of all twins are mo-mo twins.

Mo-mo twins at around 28 weeks. Born at 32 weeks.

How much should twins weigh?

Your babies measure approximately 37,5 centimeters (14.76 inches), when you’re 28 weeks pregnant with twins. The median weight for dichorionic twins is 1210 grams (2lbs, 10oz) and for monochorionic twins it’s 1163 grams (2lbs, 9oz). Look at our estimated fetal weight charts to learn more about how twins grow in the second half of pregnancy. All organs are fully formed, except the lungs. They need to mature, and your babies still need to grow bigger and stronger inside your womb. The placenta(s) is growing along with your babies. Your babies are getting all the nourishment they need from the placenta(s) through the umbilical cords.

Previous week – 27 weeks pregnant with twins

Next week – 29 weeks pregnant with twins

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Pregnancy diet, exercise & prenatal vitamins

You still need to take folic acid at 9 weeks pregnant with twins. Folic acid helps prevent neural tube defects.

There are some physical challenges you need to pay more attention to at this stage of your pregnancy. Be careful with prolonged standing – especially in stooped postures.

Avoid sudden and heavy lifting. It’s a great idea to exercise regularly. If you keep active throughout your pregnancy, you’ll be better at coping with the weight gain that comes with your pregnancy.

You are also more likely to have a better birth experience. Don’t be afraid of physical activity in relation to miscarriage. There’s no correlation as long as you don’t participate in contact sports or activities where you can fall and hurt your stomach.

Baby size & development

Your babies will measure around 2,5 cm – that’s about an inch – from head to rump at the end of this week. Their genitals are formed. You won’t be able to tell whether you are carrying twin boys, twin girls or boy-girl twins yet.

They still look very similar at this point. You will learn the gender of your babies at the anatomy scan. That usually takes place when you’re between 18 weeks and 20+6 weeks pregnant.

If you’re willing to pay for an earlier scan, you may be able to find out a few weeks earlier. You can know even sooner if you get or pay for genetic testing.

Your baby’s hearts are fully formed with four heart chambers. Your heart is still pumping the blood for your babies and back and forth between the placenta(s) via the umbilical cords.

Both the placenta(s) and the umbilical cords will grow with your babies and provide them with everything they need in the uterus.

Their arms are fully visible, but the legs aren’t yet. They develop more slowly.

Twin ultrasound pictures of identical twins

These twin ultrasound pictures are identical twins who share a placenta. They have their own separate inner sac and share the outer sac.

This type of twin pregnancy is called monochorionic-diamniotic. About 2/3 of identical twins are monochorionic-diamniotic.

Twin ultrasound pictures of fraternal twins

This twin ultrasound picture is from a fraternal twin pregnancy. Fraternal twins have their own separate placentas and their own separate inner and outer sac.

This type of twin pregnancy is called dichorionic diamniotic. Identical twins can also be dichorionic diamniotic. About 1/3 of identical twins are dichorionic diamniotic.

Pregnancy symptoms & belly pictures

When you’re 9 weeks pregnant with twins, you probably feel more tired than usual. You may have some or all of the following symptoms:

• You feel bloated, especially in the evening

• You’ve probably started to gain weight

• You may notice that you bleed more easily from your gums

• You may get nosebleeds. This is because the amount of blood in your body increases and puts more pressure on the vessels

• You might suffer from morning sickness

Previous week – 8 weeks pregnant with twins 

Next week – 10 weeks pregnant with twins

Ingredients*
5 dl water
3 dl skimmed milk
50 g of fresh yeast
4 teaspoons of salt
4 eggs (a little bit extra for the egg wash)
16 sausages  (choose high-quality meat)
400 g whole grain flour
200 g rolled oats
400 g wheat flour
Ketchup (amount as you please)

* This is for a large batch – 32 good-sized sausage rolls. If you want a smaller batch, divide the numbers with two.

How to make the healthy sausage rolls

– Warm up the water and milk.  You can use a microwave or do it on a stove. You don’t necessarily need to use a thermometer. You can check the temperature by using your (clean) finger. The liquids need to be slightly warm, but not hot. If you get much above 40 degrees Celsius you run the risk of killing the yeast. If you go below 30 degrees Celsius its growth slows down dramatically.

– Add the yeast and stir. Add the other ingredients and knead the dough well. It’s good if the dough is a bit sticky, when you leave it to rise. It needs to rise for about half an hour.

– Knead the dough again and divide it into 4 portions. Roll out each portion to a circle with a diameter of 35-40 centimeters. Spread ketchup out on each circle.

– Divide each circle into eight squares. Cut the sausages in half and use one half on each square. Roll the dough around the sausages and place them on a baking tray lined with baking paper. Make sure that the closure is downwards.

– Use an egg wash and brush it onto the surface of the sausage rolls.

– Let the sausage rolls rise again for about half an hour. Preheat the oven on 225 degrees Celsius and bake them in the middle of the oven for about 15 minutes (or until they are golden).