Am I having a big baby?

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How will I know if I’m having a big baby?

My bump seems too big

How will my baby bump be measured? 

Why might I be having a big baby?

Can I reduce the risk of having a big baby?

Will having a big baby affect my birth?

Diabetes and suspected macrosomia

Will my baby’s health be affected?

Giving birth to a big baby can be a common worry for pregnant women and birthing people. But most big babies are born healthy and your birth plan (how you want to give birth) may not necessarily be affected.

How will I know if I’m having a big baby?

It can be hard to tell for sure if your baby is big before they are born. Your midwife may suspect your baby is big when they start measuring your baby bump. An ultrasound scan may also show a big baby. 

When a doctor or midwife thinks your baby might be big from bump measurements or scans, it’s called macrosomia or ‘large for gestational age’. Giving birth to a big baby can be a common worry for pregnant people. But most big babies are born healthy and your birth plan may not be affected.

Remember that your midwife is there to listen to any concerns you have about pregnancy. There are no silly questions. So, if you have any concerns about how your baby is growing, tell your midwife how you feel.

My bump seems too big

It’s difficult to tell if you’re having a big baby just from looking at your bump. Many people worry that they are having a big baby if they have a big bump. Some worry that their bump is too small and their baby isn’t growing well.

But, in the same way that every person’s body is different, every baby bump is different. If your bump seems small or large it does not mean your baby is too large or too small or that your baby is not healthy and well. Baby bumps come in all different shapes and sizes.  

How will my baby bump be measured?

Your midwife will ask you to lie down and will measure from the top of your bump to the top of your pubic bone using a tape measure. These measurements should be taken at each antenatal visit from around 24 weeks.

The measurements are mapped on a growth chart. Many hospitals are now using personalised growth charts, which take more of your personal characteristics into account, and marking your measurements on these. This makes checks on the baby’s growth more accurate.

Why might I be having a big baby?

There are many reasons why you may be more likely to have a bigger baby. This includes if you:

• have a body mass index (BMI) of over 30 during pregnancy
• go more than 2 weeks past your due date (you will likely be offered an induction of labour to avoid this)
• have type 1 or 2 diabetes or develop gestational diabetes
• were a bigger baby yourself
• are more than 35 years old.

There is limited research about how much difference the father or sperm provider’s size at birth makes to the size of your baby.

If any of these apply to you, try not to worry. This does not mean you will definitely have a big baby.  

Can I reduce the risk of having a big baby?

The best thing you can do is eat healthily and stay active during pregnancy. This will help you manage your weight gain and lower the risk of getting gestational diabetes.

If you have type 1 or 2 diabetes in pregnancy, you will get extra care to make sure your condition is well managed throughout your pregnancy. This can help reduce the risk of your baby growing larger and faster than usual. Find out more about managing type 1 or type 2 diabetes during pregnancy.  

Will having a big baby affect my birth?

If your doctor or midwife think that you’re having a big baby, this does not necessarily mean you cannot give birth vaginally, if this is what you want.  

Your doctor or midwife may not be certain that your baby is large for their gestational age until they are born, so this will need to be taken into account when you decide how to give birth.

Your doctor or midwife will talk to you about the advantages and disadvantages of giving birth vaginally and by caesarean section. Complications may include:

• medical problems such as infection with emergency caesarean section
• shoulder dystocia, which is when a baby’s shoulder gets stuck during a vaginal birth  
• instrumental birth and perineal tear with vaginal birth.

It’s important to remember that either way of giving birth carries some amount of risk, whether you are having a big baby or not. The important thing is that you make an informed decision about your care that you are most comfortable with.  

Read our information and talk to your doctor or midwife about your options for where and how you would like to give birth. It is a good idea to write a birth plan. 

Diabetes and suspected macrosomia

Because you’re more likely to have a large baby if you have diabetes, you may be offered an early induction of labour or planned caesarean section. This will help reduce the risk of birth complications.

How you deliver your baby is your choice. Talk to your healthcare team for more information about giving birth with type 1 or 2 diabetes or with gestational diabetes.

Will my baby’s health be affected?

Most big babies are born healthy. Jaundice is common in newborn babies and especially in babies of mothers with diabetes. This is a common and usually harmless condition in newborn babies that causes yellowing of the skin and the whites of the eyes. Jaundice is caused by the build-up of bilirubin in the blood. Your baby may need to be monitored in the neonatal unit. 

Visit NHS to find out more about newborn jaundice.

What is shoulder dystocia?

In some cases (just under 1 in 140 births) a baby’s shoulder can get stuck after their head has been born during a vaginal birth. This is called shoulder dystocia. It sounds scary, but your doctors and midwives will move quickly to release your baby's shoulders. 

Shoulder dystocia is more likely to happen if you are having a large baby, but it can happen with smaller babies too. Other things that mean that shoulder dystocia is more likely to happen include if you:

• have had shoulder dystocia before  
• have diabetes  
• have a body mass index (BMI) of 30 or more  
• have labour induced  
• have a long labour
• have an assisted vaginal birth (forceps or ventouse).   

If your baby’s shoulder is stuck, it needs to be released quickly so that they can be born fully and can start breathing air into the lungs. Your doctors and midwives are well trained, highly skilled and prepared for this situation.  

They may:

• ask you to stop pushing  
• ask you to change position
• make a cut (episiotomy) to enlarge the vaginal opening  
• press on your tummy to release the shoulders.

1 in 10 babies affected by shoulder dystocia may have injuries such as damage to the nerves of the arm, or a fractured arm or shoulder, which should heal. The nerve damage may lead to loss of movement in their arm that usually gets better with time.

In very rare cases, a baby may suffer from brain damage if they didn’t get enough oxygen because their delivery was delayed. But in most cases of shoulder dystocia, babies are born quickly and safely.

Find out more about your baby’s health if you have type 1 or type 2 diabetes or if you have gestational diabetes.

Regardless of their size at birth, a baby's weight is always monitored closely after they are born to make sure they are healthy and growing properly. But their weight isn't the only thing that's important. How your baby is feeding and the number of wet nappies and poos they do every day can also indicate that your baby is doing well. 

Find out more about after your baby is born.

Talk to your doctor or midwife if you have any questions about your baby’s growth during pregnancy. You can also call speak to our midwives on our pregnancy line on 0800 014 7800 (Monday to Friday, 9am to 5pm), or email us at [email protected].