Objective: to assess levels of intra-observer and inter-observer variability in the measurement of postnatal symphysis-fundal distance and establish whether the measurement is sufficiently precise for it to be of use in clinical practice.
Setting: a consultant obstetric maternity unit in the south of England which caters for approximately 6000 deliveries per annum.
Methods: in the intra-observer study 15 midwives took repeated readings of symphysis-fundal distance on 30 postnatal women. In the inter-observer study 13 midwives took readings of symphysis-fundal distances on 24 postnatal women. Repeatability coefficients (the variability to be expected in the change between two measurements) were calculated.
Findings: the repeatability coefficient, that is the maximum difference that is likely to occur, 95% of the time, for the difference between two measurements obtained by the same midwife on the same woman is 2.94 cm (intra-observer study). Where measurements are obtained by different midwives on the same mother the repeatability coefficient is 5.01 cm (inter-observer study). In everyday clinical practice variability is likely to be greater than that found in this study.
Implications for practice: the daily measurement of the postnatal symphysis-fundal distance with a tape measure cannot be obtained with enough precision to be useful in making clinical judgements and therefore should be discontinued. Further research is required to assess the value of routine palpation of the uterine fundus to assess involution during the postnatal period.