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From around 24 weeks of pregnancy, you’ll probably be offered a symphysis fundal height measurement at most of your antenatal appointments. It’s often done so routinely that you might not have realised it’s a screening test that you can choose to have or not have. As independent midwives in Kent, we’re passionate about making sure you have the information you need to decide what’s right for you. In this post, we’ll look at what measuring your bump can tell you, where it falls short, and how to make an informed choice that feels right for you.

What Is Symphysis Fundal Height?

Symphysis fundal height refers to the measurement between the top of your pubic bone and the top of your uterus, which is called the fundus. It’s measured in centimetres and generally this will match the gestation. So for example, if you’re 32 weeks, we would expect the measurement to be around 32cm. A general rule of thumb is that there’s a 3cm leeway either side, so anywhere between 29-35cm would be considered normal growth. The number is then either plotted on a standardised or customised growth chart depending on what your local Trust is using or what you have consented to. More on these charts below! The aim of measuring is to detect babies that are not growing as expected.

How a midwife measures your bump

Your midwife should gain your consent prior to measuring your symphysis fundal height. This means explaining what the measurement is for and the potential benefits and the limitations of the measurement. Informed consent also means having the opportunity to say no, so they should ask if you would like to have the measurement taken or not. If you give your consent, then your midwife will ask you to lie down and expose your belly. They’ll feel your belly to assess where the top of your uterus is and then hold the tape measure in place there and measure to where the top of your pubic bone is. Usually the tape measure is facing down so that the numbers can’t be seen to try and prevent any bias. They should then tell you what the measurement is and document it in your notes.

When measuring usually starts and how often it’s offered

NICE guidelines recommend offering symphysis fundal height (SFH) measurements from 24 weeks of pregnancy, no more frequently than every 2 weeks. If you’ve got an uncomplicated pregnancy and are having routine care, you can expect to be offered a measurement at every appointment after 24 weeks.

Why Is Fundal Height Measured in Pregnancy?

Monitoring your baby’s growth

Fundal height measurements are a simple, low cost and low tech tool with the aim of assessing a baby’s growth. A baby that isn’t growing as much as expected could be a warning sign of something more serious, for example placental insufficiency.

Customised and standardised growth charts explained

If you’ve agreed to have your bump measured, your midwife will plot the number on a growth chart to track it. Customised growth charts have been tailored to your pregnancy and will usually take into account your height, weight, ethnicity and the birth weight of any other babies you might have had. Standardised growth charts are based on population level data. Both charts will feature lines that represent different centiles, which are often the 3rd, 10th, 50th, 90th and 97th centiles. Some NHS Trusts will provide a printed copy in your notes and plot measurements here. Where Trusts have ‘gone digital’ the data may be inputted onto a computer system and depending on your Trust you may or may not have access to this information. Side note: you should have easy access to all your maternity notes. In our experience we’ve found this varies quite a lot from hospital to hospital especially with the digitalisation of notes and different online systems being used by different NHS Trusts.

Customised growth charts make sense in theory and are a feature of the Perinatal Institute’s Growth Assessment Protocol (GAP). This 2022 research looked at the GAP in England and revealed that in fact it didn’t make a difference in the detection of small for gestational age babies when compared to standard care. Anecdotally, we are aware of some NHS Trusts having moved away from using the GAP.

The Strengths of Measuring Fundal Height

Simple, cheap and non-invasive

Fundal height measurements are incredibly low tech, cheap and non-invasive. In some cases an unexpected fundal height measurement might be the first sign that something is not quite right and will prompt the offer of further investigation.

A chance for hands-on connection with your midwife

If you see the same midwife, having your fundal height measured is an opportunity for hands-on connection. The midwife can also offer an abdominal palpation to assess your baby’s position. You can choose to have both these things, one of them or none of them.

The Limitations of Fundal Height Measurement

How accurate is it?

Rachel Reed highlights within her lesson on Big Babies (available to members of the Reclaiming Childbirth Collective - anyone can join) that fundal height measurements were initially developed to assess the gestation of a pregnancy rather than to track growth. Over time the measurement has evolved to be used as a screening assessment for fetal growth and if we’re being honest, they’re not a very good tool for doing so. A 2015 systematic review (where lots of research papers are included and the results analysed) found that small for gestational age (SGA) babies could be missed in over 70% of cases with fundal height measurements. In contrast, for babies that were large for gestational age (LGA) a 2004 review found that fundal height measurements were wrong 50% of the time.

Factors that affect the measurement (e.g. position, BMI, fluid, fibroids, twins)

There are several factors that can affect your fundal height measurements. The position of your baby can change the measurement dramatically - for example if your baby is lying sideways (also called transverse), your SFH will likely measure much smaller than expected. If you have a higher BMI the measurement might be much bigger than expected. Even, in our experience, just the way you carry your baby and the shape of your body can make for measurements that don’t align with what’s expected. Things like too little or too much amniotic fluid can give smaller or larger measurements. If you have large fibroids these may also increase the measurement - depending on where they are in your uterus. If you are expecting twins (or more) NICE guidelines don’t recommend offering fundal height measurements as there’s no way of even remotely assessing the growth of each individual baby this way - instead regular scans are offered throughout pregnancy.

The other thing that can affect the measurement is the clinician doing it. Having the same midwife measuring will be less likely to lead to inconsistent measurements and potential panicked referrals for scans. If you have multiple different midwives measuring they may all be using slightly different landmarks which can affect the measurements. Whilst we can’t say that SFH measurements are accurate, it is another area where having the same midwife (also known as continuity of carer) is really useful.

What happens if your measurement is “off the chart”?

If you have a measurement that is much smaller than expected you’ll be advised to have an ultrasound scan and to speak with a doctor. The urgency of this scan takes into account the whole clinical picture, including things like your baby’s movements and if you have any signs of pre-eclampsia, for example.

On the other hand if your measurement is much larger than expected, NICE do not routinely recommend offering an ultrasound scan - they say to consider one. In our experience however, scans are being offered when measurements are bigger than expected. This is again a scenario where we want to be looking at the full clinical picture. Sometimes things like uncontrolled blood sugars (due to gestational or pre-existing diabetes) can mean you grow a larger than expected baby. Rachel Reed talks about gestational diabetes in this post if you want more information on that.

Your Right to Choose: Informed Consent and Bump Measuring

You can decline, ask questions or request alternatives

It’s always your choice if you want to have your symphysis fundal height measured in pregnancy or not. Your consent should never simply be assumed. If you do decline, your midwife may explore the reasons why with you (and we would argue this is good practice and part of a holistic approach!) but they should always respect your decision. You should also know that you can change your mind at any point, but in the same breath you can ask that you are not asked at every single appointment if you want to. This will be easier to achieve with continuity of care, as your midwife will already know your preferences.

The alternative method for assessing fetal growth is by ultrasound scans. Some NHS Trusts have introduced routine 36-week scans for all women, regardless of risk factors, and so no longer use fundal height measurements. If you have certain risk factors you may be offered serial growth scans in pregnancy, instead of fundal height measurements. It is worth noting that ultrasound scans have a 10-15% error margin when it comes to assessing fetal weight - so they also can’t be said to be reliable when it comes to monitoring growth.

Questions to ask your midwife before measuring

You might want to ask what the recommendations are (both national and local) in the event that the measurement is smaller or larger than expected. Understanding this may help you decide if you want to have the measurement or not. Using the BRAINS decision making tool can also be helpful in these scenarios.

Making a decision that feels right for you

Only you can make the choice that feels right for you when it comes to fundal height measurements and indeed anything in pregnancy. It’s worth thinking about before you get to 24 weeks so that you don’t feel put on the spot in the moment, especially if you are on the fence about having the measurements.

How Juno Midwives Approach Fundal Height Measurement

Continuity of care with your own midwife in Kent

We offer all our clients fundal height measurements from 24 weeks as per NICE guidelines. We’ll go through the pros and cons and potential limitations of measurements with you so that you can make an informed choice. If you do choose to have measurements, that’s fine by us, but we’ll always ask for your consent each and every time. If you decline measurements, that’s also fine by us! We may offer them at subsequent visits depending on if you want us to or not. You might never want to hear another word about them again - and we’ll respect that if so. Another thing we do at each appointment is ask you how you feel your baby is and how you feel they’re growing. You really do know your baby best and we trust your wisdom and intuition on their wellbeing too.

Frequently Asked Questions

Does measuring my bump hurt?

It shouldn’t hurt to have your bump measured. As your pregnancy advances it may get more uncomfortable to lie semi-recumbent to have the measurement itself taken and some people might find their pubic bone area is quite sensitive due to symphysis pubis dysfunction (also known as pelvic girdle pain). The pressure of the tape measure should never be such that it gives you pain - the person doing it is doing it wrong if so!

Will I need a growth scan if I measure small or large?

You’ll need to find out what the policies are around this in your local area. A smaller measurement generally prompts a scan referral but a larger measurement doesn’t automatically and isn’t routinely recommended by NICE guidelines. However the NHS is very risk-averse, so in our experience a scan is often offered where a measurement is larger than expected.

Do I have to have my bump measured?

No! Everything in maternity care is an offer. You should be offered the choice, after an explanation of what SFH is and what it’s looking for, along with potential benefits, risks and an understanding of the recommendations if the measurement isn’t as expected. If you decline measurements your decision should be respected.

Independent Midwifery Care in Kent

We offer private, independent midwifery care in Kent. You can book us from the moment you find out you’re pregnant and we can be by your side until 4 weeks after your baby is born. We specialise in supporting home birth, but can also provide non-clinical advocacy for hospital births or planned caesarean births. Our care focuses on you and what you want for your pregnancy, birth and postpartum experience. We have the time to discuss all your options and we are passionate about supporting you to make the choices that feel right for you.

If that sounds good, book your free intro chat today. We can’t wait to meet you.