Reducing the risk: stillbirth prevention strategies

Stillbirth prevention strategies vary between HICs and LMIC as the causes are very different. In LMIC, the strategies must focus on the provision of basic antenatal and intrapartum care.

The recent series on stillbirth in The Lancet has emphasized the fact that even in HICs there is significant variation in stillbirth rates between countries with similar populations and health systems sug­gesting that there is a lot that can be done to improve rates through prevention strategies. Even within HICs there are major differences as a result of socioeconomic disadvantage, which is particularly seen in Indigenous populations across the world such as those in Australia and Canada.

The role of risk factors identification and early delivery in stillbirth prevention

The knowledge of healthcare providers in HICs of the importance of risk factors has been surveyed revealing some interesting re­sults, in which some less important risk factors are overemphasized, while the significance of others is underestimated (3). Maternal age, overweight and obesity, and smoking are three significant modifi­able risk factors, which collectively contribute to about 30% of still­births. However, knowledge of the importance of risk factors does not easily translate into clinical practice. Smoking cessation advice can improve outcomes but as smoking rates fall, this is becoming less important from a population perspective. Average maternal age continues to increase in most HIC, as do rates of overweight and obesity and the most frequently used intervention is early delivery.

The use of ultrasonography in the prediction of stillbirth risk

FGR and placental dysfunction with a range of placental pathologies are frequently found in association with stillbirth. Clinical detection of reduced fetal growth is generally not accurate enough to detect all those late gestation fetuses that are vulnerable. This is in part be­cause of the inherent inaccuracy in fundal height measurements caused by variation in the measurement, but also because some of those at greatest risk may be those that show late slowing of growth. The early randomized trials of routine third-trimester ultrasound scanning, with or without umbilical artery Doppler, did not show improved perinatal outcomes although stillbirth prevention was not the primary outcome of most studies. Ultrasonography is used more frequently in those with risk factors such as maternal obesity but many late gestation stillbirths occur in women without risk factors. There is a resurgence of interest recently in the use of ultrasound bi­ometry to improve the detection of FGR, as well as other modalities such as fetal Doppler making use of the cerebroplacental ratio. The ratio of middle cerebral artery Doppler pulsatility index to that re­corded in the umbilical artery is a marker of cerebral redistribution of blood flow. The concept that placental dysfunction may occur in apparently normally grown fetuses, but which show redistribution of blood flow to the fetal brain, is now of significant interest as a still­birth prevention strategy and requires confirmation by large clinical trials (3).

Predicting stillbirth risk in early pregnancy

In many respects, the ideal strategy is to predict stillbirth risk in early pregnancy and then introduce a treatment that reduces the risk. At present, the only candidate for this is low-dose aspirin but other strategies may be developed in the future. First-trimester uterine artery Doppler, coupled with biomarkers such as pregnancy- associated plasma protein A (PAPP-A), can predict an increased risk of FGR, and indirectly the risk of stillbirth, but this needs further evidence before it can be recommended as an effective prevention strategy. As further research is done there may be other biomarkers identified that can be used for the same purpose.

Monitoring fetal movements, and organizational responses to decreased fetal movements

It has been known for decades that DFM is a predictor of stillbirth, yet evidence from large randomized trials shows that routine fetal

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Figure 34.4 Colour Doppler imaging of the fetal circulation enables waveforms from both the (a) cerebral (middle cerebral artery) and (b) umbilical circulations, and enables the calculation of a CU ratio which can show evidence of redistribution of blood flow in the vulnerable fetus.

movement counting does not appear to reduce stillbirth risk. This may be the result of poor response to maternal presentation with DFM, coupled with a lack of appreciation of stillbirth risk factors. A nationwide approach in Norway to raising awareness of DFM has shown promise as a population-based prevention strategy but this is yet to be confirmed in other countries. DFM is a common pres­entation in the third trimester, and often there is reassurance from a normal CTG, without further investigation or an objective assess­ment of risk factors for stillbirth.

Other interventions (including maternal sleep position)

A potentially important finding was reported in 2011, following a case-control study in Auckland, New Zealand, which showed an association between maternal back sleeping and late gestation still­birth (13). Since then, this observation has been replicated by other similar studies in Sydney, Australia, and West Africa. The possibility that this is part of the causation of stillbirth is an attractive idea as there is some biological plausibility based on the theoretical risk of reduction in uterine blood flow caused by the gravid uterus. Despite considerable interest, the association has not yet been confirmed by studies that prove conclusively the risk of stillbirth can be reduced by not back-sleeping. Part of the problem is the issue of maternal recall of sleeping position after such a traumatic event as the loss of a baby. If maternal sleeping position is part of the mechanism of late gestation stillbirth, possibly coupled with some degree of fetal vulnerability based on placental dysfunction, the intervention to re­duce risk is likely to be an educational campaign aimed at changing maternal behaviour. However, many of the parent advocacy groups involved with stillbirth have already started to promote this idea so it may already be very difficult to study this intervention.

Much of the recent research has focused on late gestation stillbirth as the category where there appears to be the most potential for pre­vention. However, earlier gestation stillbirth (20-28 weeks) is now becoming a more prominent feature of perinatal mortality reports and it is important not to forget that this is an equally tragic outcome of pregnancy. More research needs to be done to try to understand the likely cause of these earlier fetal deaths, as any approach to pre­vention needs to be targeted based on evidence.

Stillbirth prevention strategies must target the most common causes if they are going to have a significant impact. Investigating stillbirths thoroughly, and performing rigorous perinatal mortality audit to classify cases by antecedent cause (including any contribu­tory factors in care), is an essential part of any prevention strategy. Only in this way will interventions be accurately targeted to prevent­able causes of stillbirth.