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Twins Not Growing At Same Rate: Should You Be Worried?

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When a mother discovers that they are having twins, they realize that they have to take care of two people and monitor their development at the same time.

Most people think that twins will grow at the same rate, but the truth is that there is a slight difference in their weight even if they have the same gestation period.

However, when you see your twins not growing in utero at the same rate, you start to get worried. But should you be?

Why Are My Twins Not Growing at The Same Rate?

There are several reasons as to why your twins may not be growing at the same rate. When doing an ultrasound, your doctor will give you an overview of their current size and possible weight.

two newborn twins

If your doctor tells you that one is bigger than the other, you may wonder why it is happening and how it may affect either of your babies.

To give you an idea of what creates the difference in growth, here are some reasons:

  • If you have monoamniotic monochorionic twins, the babies may be vying for the nutrition that they are getting. It is not something you can control because it is a biological event. It is up to your babies to get as much nutrition as they need within one amniotic sac and from one placenta.
  • If you have diamniotic dichorionic twins, this means that they are taking their nutrients from separate placentas and are gestating in different amniotic sacs. Again, this is a biological factor that you cannot change. Your babies will get the nutrition they want and need, but the rate of their growth is still affected by the amount of nutrients they get from your body.
  • When you are having twins, their growth rate will inevitably slow down by the 30th week. It is not a cause for alarm because it is natural for twins to grow slower because they are getting their nutrition from one body.

Are You The Reason Why Your Babies Are Not Growing at the Same Rate?

Of course not! It is not your fault if your babies are not growing at the same rate. However, you can help improve their condition by improving your diet based on a prenatal nutritionist or your doctor’s advice.

If, however, you are not eating enough or are eating nonhealthy food, the growth of your twins may slow down earlier or faster. That is why it is important to always eat healthy food and the right amount to avoid underfeeding or overfeeding your twins in the womb.

You also have to factor in external circumstances such as complications in the womb or your body. For example, if you get sick, the three of your will compete for nutrients.

If you ingest something that stumps your babies’ growth, then you may have to work harder to get them back to a healthy size and weight.

It all boils down to how you take care of your body and what your doctor finds during every visit. This is why it is important to take all your vitamins, eat healthier, and always follow your doctor’s advice.

It never hurts to have a second or third opinion, especially if you are extremely worried about the growth gap between your twins.

Fraternal Twins Growing at Different Rates

Fraternal twins may grow at different rates for several reasons. If they are the same gender, there is little difference in how they metabolize their nutrients. If they have different sexes, there is a possibility that the male twin may be absorbing more nutrients than their sister.

identical twin babies

Many fraternal twins, whether they are mono-mono or di-di, can grow at different rates while in utero, especially if they share a placenta. It is much more likely that they have different growth rates because they are from two completely different egg cells, thus, giving them more biological autonomy than identical twins.

Identical Twins Growing at Different Rates

Because of the extreme similarity in their biological makeup, identical twins may react the same way to how your body is gestating. There may be little difference in their growth, but nature will always be a factor. Your twins may start to grow at different rates regardless of their status as identical twins.

The reason for this is biological feedback. If one twin feels that they are not getting enough nutrients, their body will start to take in more from your placenta. If the other baby does not react the same way, they may grow more slowly because their body did not react the way the other baby’s did.

When Should I Worry About The Growth Rate of My Twins?

The only time you should worry about your twins’ difference in growth rate is when your doctor says so. They are obligated to tell you about any complications that arise during your pregnancy, which means that they will never hide any problems from you no matter what the case.

If you are curious to know when doctors start to worry about difference in growth rates, here are some factors that go into their decision:

  • They noticed an abnormality in the amniotic sac, umbilical cord, or placenta.
  • The size gap between your babies is too significant to ignore. The decision depends on the doctor, but an example would be twins that have significant difference in percentile weight. Baby 1 might be in the median fetal weight percentile, while baby 2 might be less than the 10th percentile. If this is the case, the doctor will request for more tests such as higher frequency ultrasounds, blood tests, amniocentesis, etc.
  • The fetal heart rate of one baby is significantly lower than the other. When alarm bells ring, that’s when you know there is something wrong with one of the baby’s growth.

What Should You Do If There is a Problem With Your Twins’ Growth?

Always follow your doctor’s advice. If there is a problem, they will do their best to fix it. However, you have to do your part as well.

It may be traumatic to learn that one of your babies may be in danger, but worrying about it and stressing too much will only make things work. The best way for you to approach the problem is by preparing yourself for any possibilities and making sure that you and your doctor have a plan in place.


Remember, twins are not like singletons. They have to compete for their nutrition, but you can always fix that by eating as many healthy food as you can. Just make sure that your babies don’t become overweight in the womb as this will cause complications as well.

If you have any other questions about twins not growing at same rates, do not hesitate to ask.



  1. I have fraternal twins, and as of 9 weeks they were measuring one week ahead, and now a one baby is not measured ahead and is measuring normal as for the other baby it’s measuring ahead still.

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