Fundal Height (Fundal Height Measurement and Plotting)

B1 Why can we not use the conventional rules and charts for fundal height?
As is the case with fetal weight, the growth of the uterine fundus also varies with pregnancy characteristics. The old rule of [gestational age in weeks] = [fundal height in cm] is simply not true, and acceptance of a normal range of +/- 2 or 3 cms is unsafe if not dangerous, as a fetus not growing for up to 6 weeks could be passed as normal.
B2 Why do you call it ‘fundal height’ (FH) if the usual term is symphysio-fundal height (SFH)?
The easiest and most accurate way to measure the size of the uterus is to have both hands free for palpation to determine the precise location of the fundus; the beginning of the tape can be fixed there with one hand, and the other hand then takes the tape downwards for the relatively easy task of finding the top of the symphysis pubis. Thus the recommended measurement is from the variable point to the fixed point. Symphysio-fundal height is a misnomer as it suggests that the measurement is done the wrong way around.
B3 Is it ok to start fundal height measurements from 25 weeks as we have an appointment then?
The Perinatal Institute recommends starting at 26-28 weeks. Measurements can be made earlier to coincide with appointments, but the normal range gets narrower the earlier the gestational age, and this can increase the false positive rates and result in unnecessary maternal anxiety.
B4 Why does the chart start at 24 weeks when you do not recommend fundal height measurements until 26-28 weeks?
The chart starts at 24 weeks so that estimated fetal weights (EFW) can be plotted from this gestation, as some women with increased risk factors will commence serial scans from 24 weeks.
B5 When there is a mal-presentation, how would you perform the fundal height measurement?
Regardless of the presentation of the fetus, the fundal height measurement should be performed using the standardised fundal height technique and referral made for an ultrasound scan if the plotted measurement does not follow the expected trajectory of growth.
B6 Why is it important for the woman to have an empty bladder when measuring fundal height?
A full bladder can lift the uterus up and would therefore give a false fundal height measurement.
B7 If a woman is seen in the day assessment unit for whatever reason and she has had her fundal height measured within the last two weeks, should she be re-measured?
Apart from the investigations indicated by the clinical picture, we recommend measurements to be spaced 2-3 weeks apart, allowing time for growth, and preferably by the same person to reduce inter-observer variation.
B8 Should I undertake a fundal height measurements if a woman is admitted with spontaneous rupture of membranes?
While there is little available evidence, we consider fundal height measurements as useful in pre-labour SROM, as the amount of fluid lost is usually small and unlikely to affect the measurement significantly. Most of the liquor tends to get reconstituted but the presence of oligohydramnios is an indication for ultrasound scan assessment.
B9 What do we do if the fundal height measurement pattern has changed when measured on admission in labour, especially in a midwifery led care environment?
Fundal height measurement at the onset of labour is part of routine assessment and should be recorded in the Birth (Labour) Notes. It is unusual for the fundus to ‘drop’ with head engagement and/or rupture of membranes, and a low fundal height measurement should raise the suspicion of ?FGR and be an indication for review.
B10 Do we need to take into account descent of the head when plotting fundal height?
Even as the head engages the height of the uterine fundus should continue to grow until delivery, and there is no flattening of the fundal height curve at term. If the measurements suggest static growth, a referral should be made for an ultrasound scan to assess fetal well being.
B11 Should fundal height measurements be continued when a mother has serial scans?
If serial scans are done according to recommended frequency (3 weekly until delivery), fundal height measurement and plotting is not required.
B12 We seem to have a lot of referrals for scans based on SFH
We have observed that this happens in units where staff had insufficient training in measurement technique and protocols - see article (MIDIRS). Common reasons for unnecessary referrals include:
  • not using standardised fundal height measurement technique;
  • not plotting against the actual gestational age;
  • assuming measurement in cm should equal gestational age in weeks;
  • first fundal height plot above 90th ;
  • consecutive measurements above 90th or below 10th centile line, even though they show normal growth I.e. slope is parallel to growth curves on chart.
A controlled trial (BJOG) showed that fundal height measurements plotted on customised charts and appropriate referral pathways do not increase the need for scans but REDUCE it because of fewer unnecessary referrals, while FGR detection rates are increased.
B13 GAP training suggests that we should be completing fundal height measurements every 2 to 3 weeks. However according to NICE guidelines multiparous women should not have a scheduled antenatal appointment between 28 and 34 weeks. What should we do?
Based on case reviews of stillbirths, we believe that, from the fetus’ perspective, and appropriate monitoring of fetal growth in the third trimester, a six week gap is too long. We therefore recommend an additional visit and assessment at 31 weeks.
B14 When I make a referral following a concern from a fundal height measurement my colleagues/obstetrician will re-measure the fundal height to decide if an ultrasound is required. What should I do?
When all staff have been trained to use a standardised technique of fundal height measurement and have completed a competency assessment, there should be direct referral for an ultrasound scan to assess fetal wellbeing with an estimated fetal weight and or liquor volume /Doppler studies. The estimated fetal weight measurement should be plotted on the customised growth chart and a plan made accordingly.
B15 If the fundal height measurements are plotting above the 90th centile, does this mean the baby is large for dates and does this indicate the need for a growth scan?
If the fundal height measurements are plotting above the 90th centile, and follow an expected growth trajectory (see example below) this is indicating that growth is normal. Fundal height measurements include skin and subcutaneous fat as well as the uterus and its contents, and should NOT be equated with fetal weight. If however growth is accelerating, i.e. steeper than the normal fundal height curves on the chart, then further tests including a scan (for EFW) and a GTT may be indicated, according to local protocol.

See here for examples.

B16 What is slow growth, and how many crossed centiles does it represent?
There is to our knowledge no evidence based definition of slow growth. Instead, we recommend using the 90th and 10th centile lines as the upper and lower limits to define ’normal growth’, and visual assessment as to whether the plotted sequential measurements follow a curve, the slope of which is within the 90th and 10th centile line ‘slope limits’. This applies to measurements of fundal height (FH) as well as estimated fetal weight (EFW).

We avoid using the term ‘crossing centiles’ as this is often misinterpreted as crossing one of the three lines on the customised growth chart (90th, 50th and 10th). A drop from 45th to 15th centile can be significant yet crosses neither of these lines.