Examination of the placenta and membranes
The placenta and membranes are examined shortly after birth to ascertain completeness. Retained placental tissue or membranes may lead to postpartum haemorrhage (PPH) or uterine infection. Information may be gained about the intrauterine environment and the wellbeing of the baby.
The term placenta is round or oval, deep red/maroon in colour, 20–22 cm in diameter and 2–3 cm at the centre and thinner at the edge. There are two surfaces – maternal (Figure 31.1) and fetal (Figure 31.2) – and two membranes.
The fetal surface lies closest to the fetus. The umbilical cord is usually inserted centrally or slightly off centre; a lateral ‘Battledore’ insertion may occur. Blood vessels radiate to the edge of the placenta (Figure 31.2).
The maternal surface has 15–20 cotyledons separated by grooves/sulci. Each cotyledon has its own blood supply (Figure 31.1).
Umbilical cord: This approximately 50 cm or more in length, and contains two arteries and a vein suspended in Wharton’s jelly (Figures 31.3 and 31.4). A thin cord may be associated with intrauterine growth restriction and a thicker cord with diabetes, macrosomia or hydrops fetalis.
Membranes: The chorion is the outer, opaque, friable membrane that lines the uterus and extends to the edge of the placenta. The amnion is the smooth, stronger, inner, translucent membrane that covers the umbilical cord (Figure 31.5).
Ensure the mother’s condition is stable, that she is comfortable, has a contracted uterus and is not bleeding excessively. Explain the rationale for the examination. Be prepared for parents to observe and to facilitate any wishes for disposal of the placenta, for example taking the placenta home or wrapping the placenta with the baby if a Lotus birth.
To prevent any transmission of a blood-borne infection, non-sterile gloves and an apron should be worn. Hands should be washed before and after the examination. Examine the placenta in good light, on a flat surface that is protected to contain blood spillage. A syringe and needle may be needed to sample cord blood.
When examining the placenta and membranes be systematic and use your senses to observe, feel and smell.
Place the placenta on a flat surface, fetal surface uppermost (Figure 31.2). Note the size, shape, colour and smell. A placenta has little odour, but if infection is present it may smell offensive. Look to see if there are any additional/Succenturiate lobes visible in the membranes. Note fatty deposits, infarctions (localised tissue death), or grey, gritty calcification (lime salt deposits). Although of interest, these are not of clinical significance
Examine the umbilical cord, observe the insertion point, note the length, any true knots or formation of thrombi.
Inspect the cut end of the cord to determine if two arteries and a vein are present, (Figure 31.4). A missing artery may signify increased risk of anomalies such as renal agenesis and will require paediatric referral for the baby.
Lift the placenta by the cord, the membranes can be observed and the hole seen where the baby has passed through the membranes. Note any vessels or placental tissue in the membranes. Turn the placenta over to examine the maternal surface (Figure 31.1).
Check both membranes are present by separating the amnion from the chorion (Figure 31.5).
Examine the maternal surface, ensure all the cotyledons are present, fit together, without gaps and with a uniform edge. Reposition any broken cotyledons and observe for completeness.
Spread out the membranes to look for blood vessels leading into the membranes that may suggest a succenturiate lobe (Figure 31.6) is retained in the membranes. If retained in the uterus, this may lead to PPH or sepsis. Again, note any greyness, grittiness, infarctions or fatty deposits.
Take cord blood samples for blood gas analysis if the baby is born by caesarean section or has a low Apgar score. Samples for blood group and Rhesus factor will be taken if the mother has a Rhesus-negative blood group.
Where maternal sepsis is suspected or confirmed, for example chorioamnionitis or prolonged membrane rupture, cord samples will be taken for blood culture. Swabs from the fetal and maternal surfaces are also required.
Follow local policies for further investigations and tests that are needed if the baby has an abnormality, or has died.
Dispose of the placenta as per local policy, or if the mother wishes to take the placenta home place this in a sealed container. If the mother has a lotus birth where the cord is uncut, the placenta may be washed and wrapped in a soft cloth and placed with the baby. The mother may be advised that separation of the baby from the placenta is likely to take several days. Any indications of infection such as an offensive smell should be discussed with the midwife.
Record your findings in the maternal notes, reporting any abnormalities to the obstetrician. Retain any incomplete placenta/membranes for further examination. Student midwives should have their examination of the placenta observed by their mentor and all records require counter signing.
Inform the mother of the results of the examination. If the placenta or membranes appear incomplete, she should be advised regarding lochial blood loss, passing clots and signs of sepsis. The mother should be advised to seek early professional advice from a midwife or doctor if she is symptomatic. The maternal notes should clearly state if the placenta or membranes are incomplete to alert other healthcare professionals that PPH or sepsis may arise postnatally.
If the mother has delivered at home and there are significant concerns about retained placental tissue, transfer to obstetric care should be considered.