Stillbirth is a major but under-researched public health problem affecting three million families each year. Following the 2011 Lancet Stillbirth Series, it has been receiving more attention, and a recent review of its causes and possible preventive strategies is very welcome.
The vast majority (98%) of stillbirths happen in low-income countries and over half of these occur during labour or delivery. But most of the research about stillbirth has been done in high-income countries.
Infections are important causes of stillbirths in poorer countries. The list includes syphilis, malaria, ascending bacterial infection and chorioamnionitis, toxoplasmosis and viruses including HIV, rubella, measles, chickenpox, parvovirus and influenza H1N1 (seasonal flu).
In high-income settings, non-communicable conditions, such as fetal growth restriction (poor growth of the baby while in the womb), diabetes, obesity, smoking and high or low maternal age, are linked with greater risk of stillbirth.
But these risk factors are increasingly important in poorer countries, where gestational diabetes is also becoming more common. Fetal growth restriction is made worse in such settings by poor nutrition and may explain over a quarter of all stillbirths. Smoking may explain around one in five.
The authors of the review say although rates of stillbirth have fallen in high-income countries, they have now reached a plateau. They think that this may reflect increasing rates of gestational diabetes, smoking, obesity (30% to 40% of all pregnant women are now obese) hypertensive disease and increasing numbers of high-risk pregnancies in women with co-morbidities such as heart disease, renal transplants and autoimmune disease.
The authors note the most cost-effective method of screening for fetal growth restriction remains unknown. The UK National Institute of Clinical Excellence (NICE) recommends fetal size be screened for at each antenatal visit from 24 weeks by measuring from the top of the pubic bone to the top of the uterus - the symphysis-fundal height. This height is then plotted on a standard growth chart derived from all pregnancies in the population.
NICE calls for research to find out if it is more cost-effective to screen for poor growth in the womb by using (a) symphysis-fundal height or routine ultrasound and (b) standard population growth charts or customised growth charts. These calls are echoed by two Cochrane reviews, which can be found here and here.
Customised fetal growth charts
Customised charts plot estimated fetal weight on ultrasound or fundal height against percentiles calculated for each individual woman, taking into account routine data on her height, weight, number of previous pregnancies and ethnic origin. The authors report that customised growth charts already show promise in detecting fetal growth restriction.
This approach identifies a third of the small-for-gestational age population, a proportion greater than that recognised by conventional population-based percentile charts. But the authors endorse calls for more research, including cost-effectiveness studies, because of the major economic implications of more ultrasound examinations in screening for fetal growth restriction.
In low-income countries, the authors recommend more birth attendants and better care before birth and during labour. In high-income countries, they highlight the need for better education to combat late booking by socially disadvantaged women, and to promote a healthier lifestyle relating to age at pregnancy, weight and smoking.
Other possible interventions?
The review does not mention two promising recent research findings. The first shows that providing written uniform instructions to women about counting the kicks of their babies may be of help. Norwegian researchers found that this, in combination with a uniform approach to management of decreased fetal movements, was associated with a 50% reduction in stillbirths in an observational, “before-after” study in over 65,000 pregnant women.
Other researchers have shown, in an observational case-control study in 465 pregnant women, that maternal sleep practices, such as lying on the right side or on the back when going to sleep, were associated with increased risk of stillbirth.
Whether stillbirth is reduced by a healthier lifestyle, counting kicks or sleeping practices merits further research. As both these last research teams have emphasised, the most reliable evidence will come from large randomised studies.
If they are eventually confirmed as effective, counting kicks and changed sleeping practices offer simple, low-cost strategies for reducing stillbirth that might be feasible in both high- and low-income settings.