April 3, 2017


By  Genevieve EZENWATA 

Involution is a process characterised by a reduction in the size of an organ due to a decrease in the size of the cells of the organ; an example of such is found in the uterus and other genital organs after childbirth (Stables and Rankin, 2010). Medforth et al. (2011), simply defined involution of the uterus as the return of the organ to its pre-gravid size, tone and position. The uterus is a hollow, pear-shaped muscular organ, anteverted and anteflexed, almost at right angles to the vagina so that its anterior wall rests partly against the urinary bladder below, and it is situated between the bladder and the rectum in the pelvic cavity (Wylie, 2005; Waugh and Grant, 2010). According to Marshall and Raynor (2014), the uterus plays a remarkable role in pregnancy with the help of pregnancy hormones such as progesterone and relaxin, by stretching and expanding in order to nurture the fetus and accommodate its growth. This expansion and activation occur in the middle layer of the uterine wall known as the myometrium, which is partly covered by an outer layer of peritoneum referred to as the perimetrium, an internal layer also lines the uterine wall and this is known as the endometrium (Marshall and Raynor, 2014). The myometrium more so, consists of plain muscle fibres which become thicker and more defined as three layers of muscles in pregnancy (Macdonald and Magil-Cuerden, 2011). These include an outer longitudinal muscle fibres which have the ability to shorten in labour as the uterus contracts and retracts facilitating descent and expulsion of the fetus, placenta and membranes; a middle oblique or spiral muscle fibres which have the ability to contract strongly acting as living ligatures to blood vessels following the separation of the placenta during the third stage of labour; and an inner circular muscle fibres that mainly assist dilatation of the cervix during labour (Macdonald and Magil-Cuerden, 2011).

Following the birth of a baby, the mother enters a period of recuperation called the puerperium which starts after the placenta and membranes are expelled from the uterus together with a substantial proportion of the endometrium, up to 6 weeks (Fraser and Cooper, 2012; Coad and Dunstall, 2011). It is a time of major social and psychological change as the new mother incorporates her infant into the family system but most significantly characterised by anatomical, physiological and endocrinological changes relating to involution and lactation processes (Blackburn, 2013). Physiological processes resulting to uterine involution involve ischaemia, autolysis and phagocytosis (Stables and Rankin, 2010). In other words, it involves a process of uterine contractions, breakdown of the myometrial cells and epithelial regeneration and proliferation (Blackburn, 2013). Lewis (2015) explained that, oxytocin released from the posterior pituitary gland of the hypothalamus continues to induce strong intermittent contractions following birth, which may be further increased by the infant suckling at the breast. The myometrial oblique fibres acting as living ligatures occluding blood vessels supplying the placental site causing ischaemia, as well as the activation of the coagulation cascade, and the pressure of the uterine walls becoming realigned in apposition, result to haemostasis (Marshall and Raynor, 2014; Lewis, 2015).The breakdown of myometrial cells (autolysis), involves the removal of the redundant actin and myosin muscle fibres and cytoplasm by proteolytic (self-digesting) enzymes and macrophages; the excess fibrous and elastic tissues are removed by phagocytosis (Stables and Rankin, 2010). Lewis (2015) added that, the decidual lining (endometrium) degenerates and sheds as part of postpartum blood loss known as lochia, which varies in amount and colour.
According to Coad and Dunstall (2011), the puerperium is sometimes considered to be the ‘Cinderella’ of midwifery and the effects of pregnancy on maternal health post-delivery receive little emphasis. Therefore, the midwife’s role is to observe and monitor changes and be able to differentiate between normal maternal physiology and abnormality. This is because, the puerperal mother could be very vulnerable to physiological stress which would potentially lead to a pathological condition (Coad and Dunstall, 2011). NMC Rules and Standards (2012) emphasised that, the midwife is expected to provide care to women and babies in the postnatal period for not less than 10 days or for such longer period as considered necessary. More so, relevant healthcare professionals such as the midwife, who care for mothers and babies should have demonstrated competency and sufficient ongoing clinical experience in undertaking maternal and newborn physical examinations and recognising abnormalities (NICE, 2015). Fryer-Croxall and Bailey (2014) maintained that, mother and baby should remain in the midwife’s care irrespective of birth setting whereby the midwife should undertake immediate and then regular observations of fundal height, the degree of uterine contraction and blood loss. However, according to NICE (2015), assessment of the uterus by measuring fundal height or abdominal palpation is not necessary as a routine observation in the absence of abnormal vaginal loss but can be done in women with excessive or offensive vaginal loss, abdominal tenderness or fever; any abnormalities in the tone, size or position should be evaluated and other causes of symptoms considered if no abnormality is detected. Thus, the rationale for post-partum uterine palpation remains inadequate as noted by Johnson and Taylor (2016), and Bick et al. (2009), identified a need for better evidence in this area of care.

The progress of involution is usually assessed by the midwife by measuring the distance between the uterine fundus and the symphysis pubis either by abdominal palpation (anthropometry) or with a tape measure (Macdonald and Magil-Cuerden, 2011). An initial palpation of the uterus post-delivery, as recommended by Johnson and Taylor (2011), should be undertaken to establish a baseline from which the uterus is seen to involute thereafter. The size of a non-gravid uterus is 7.5 cm long, 5 cm wide and 2.5 cm deep while in pregnancy, the uterus by term has grown to 20 cm in length, 2 cm in width and 22.5 cm in depth; weight wise, there is a 20 fold increase of the uterus from 50 grams to about 1200 grams at term (Stables and Rankin, 2010). Immediately after birth, the uterus reduces in weight from 1000 grams to 60 grams and in size from 15 cm long, 11 cm wide and 7.5 cm deep to 7.5 cm in length, 5 cm in width x 2.5 cm in depth by 6 weeks postpartum. The rate of involution is considered to be approximately 1 cm per day (Johnson and Taylor 2016; Medforth et al., 2011). The uterus lies about halfway between the umbilicus and the symphysis pubis following birth and over the next 12 hours, the uterine fundus rises to the level of the umbilicus (Lewis, 2015). On the first day, it is 12 cm above the symphysis pubis, approximately 5 cm by the 7th day and barely palpable by the 10th day (Medforth et al., 2011). Lewis (2015) added that, the fundal height continues to decrease by about 1 cm per day and by two weeks, the uterus has descended into the pelvis and the fundus can no longer be abdominally palpable. Although, according to Cluett et al. (1997), there appears to be a considerable variability in the pattern of involution between women and in the daily rate of decline experienced by women individually.

 Cleutt et al. (1997), noted a decline in distance between the symphysis pubis and the uterine fundus slow enough to trigger clinical referral in women with no problems. Due to the wide variability in the pattern of involution, normal or abnormal involution could not be differentiated, thus, the symphysio-fundal distance would have to differ substantially to identify women with uterine complications; a decline of less than 1 cm over 3 or more days was defined as slow (Cleutt et al., 1997). Lewis (2015) and Bick et al. (2009), described a slow, delayed or incomplete involution as sub-involution and highlighted causative factors such as, ineffective uterine contractility, retained products of placenta and membrane fragments, as well as infection. Bick et al. (2009) added that, variability in the pattern of decline could be greater amongst multiparous women and those who had caesarean section. Medforth et al. (2011) emphasised that, involution tend to be slower after a caesarean birth and will be delayed if there is placental tissue retention or blood clot, particularly if associated with infection. It is noteworthy as stated by Lewis (2015) and Blackburn (2013), that the process of involution and restoration of the endometrium could be reflected in the characteristics of lochia which varies in amount and colour as involution progresses. The pattern of lochial loss also varies between individuals but generally starts as a reddish-brown vaginal loss known as lochia rubra lasting the first few days or through the first week postpartum, changing to pinkish-brown discharge known as lochia serosa lasting approximately two to three weeks and becoming whitish-yellow discharge know as lochia alba which can last up to six weeks postpartum (Lewis, 2015; Blackburn, 2013).

In assessing uterine involution, Lewis (2015) maintained that, this should be done after the woman has been asked to empty her bladder. Assessment should include, position, height, tone and comfort of the uterus; the uterus should be well contracted. (Johnson and Taylor, 2016). Marshall and Raynor (2014), Johnson and Taylor (2016) and Medforth et al. (2011), outlined good practise steps for abdominal palpation of the postpartum uterus and this is highlighted in a flow chart below. As emphasised by Johnson and Taylor (2016), the midwife should; communicate effectively, carryout physical examination if indicated in accordance with standard precaution and infection protocols, be able to recognise deviations from normal and instigate referral, educate, explain, support women and keep appropriate records. Palpating the uterus is not just about determining the rate of its reduction in size in relation to the postnatal day, it should be carried out as part of a holistic examination through direct sensitive questioning and observation (Bick et al., 2009). In combination with other observations such as hyperthermia, tenderness of the abdomen and offensive vaginal loss, assessing uterine involution can help to detect any maternal morbidity (Marshall and Raynor, 2014). Ideally, a documented, individualised postnatal care plan should be developed with the woman in the antenatal period or as soon as possible after birth which should include relevant factors from the antenatal, intra-partum and immediate post-partum period, details of the healthcare professionals involved in her care and that of her baby, and plans for the postnatal period (NICE, 2015).

Summarily, uterine involution is a normal puerperal physiology which can potentially change to a pathological condition. The role of the midwife to be able to recognise abnormalities and be competent in undertaking uterine palpation cannot be overemphasised. Information gathered through review of relevant literatures had shown insufficient evidence-based rationale that supports routine assessment of uterine involution by abdominal palpation or measurement in the absence of abnormal indicators such as tenderness of the abdomen, high body temperature, offensive or excessive blood loss. 

However, it is suggested that an initial palpation of the uterus post-delivery should be undertaken to establish a baseline from which the uterus is seen to involute thereafter. The process by which uterine involution occurs involves ischaemia, autolysis and phagocytosis and the progress of involution is usually assessed by measuring the distance between the uterine fundus and the symphysis pubis either by abdominal palpation or with a tape measure. Assessment is aimed at evaluating uterine tone to rule out sub-involution or any abnormality and to ensure a gradual normal progress. The rate of involution is approximately 1 cm per day however, there appears to be a considerable variability in the pattern of involution between puerperal women and in the daily rate of decline experienced by women individually. Due to this wide variability, normal or abnormal involution could not be differentiated, thus, the symphysio-fundal distance would have to differ substantially to identify women with uterine complications. Comparing theoretical principles and guidelines to what is obtainable in practice settings, it is apparent that abdominal palpation of the uterine is usually undertaken as a routine procedure which contradicts NICE guideline. On the other hand, the procedure is usually carried out as part of a daily head to toe assessment that involves getting an insight on the general well-being of the mother, taking observations of vital signs, estimating blood loss, therefore, making the procedure routinely worthwhile.

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Blackburn, S. T. (2013) Maternal, Fetal and Neonatal Physiology: A Clinical Perspective. 4 edn. USA: Elsevier.

Cluett, E. R., Alexander, J., Pickering, R. M. (1997) ‘What is the Normal Patten of Uterine Involution? An Investigation of Postpartum Uterine Involution Measured by the Distance Between the Symphysis Pubis and the Uterine Fundus Using a Paper Tape Measure’, Midwifery Journal, 13(1), pp. 9-16.

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Fryer-Croxall, C., Bailey, E. (2014) ‘A Woman-led Approach to Improving Postnatal Care’, The Practicing Midwife, 17(7), pp. 21-23.

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Stables, D., Rankin, J. (2010) Physiology in Childbearing with Anatomy and Related Biosciences. 3 edn. Edinburgh: Bailliere Tindall.

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