In 2011 a research trial in New Zealand made links between the risk of stillbirth and babies’ movements, and other factors in pregnancy including, smoking, detection of small babies and the mother’s sleep position. Some of these factors were already known, but some were not. Sleep position in pregnancy was not previously considered to be a risk factor for stillbirth.
In 2015 another research study in Sydney found that sleep position was linked to stillbirth.
As both of these research trials were small, it was recommended that further research be carried out to test the hypothesis and the Midlands and North of England Stillbirth Study (MiNESS) was established to take this forwards, funded by Cure Kids (a New Zealand charity), Action Medical Research, Tommy's and Sands.
At the same time, a similarily-sized multicentre trial was also funded in New Zealand, also by Cure Kids.
In the MiNESS study, 291 women who had a stillbirth at or after 28 weeks gestation completed a detailed questionnaire and talk to a research midwife about their sleeping habits amongst many other aspects of their pregnancy. They were not told the purpose of the study. These answers were compared with those given by 738 women who had a live birth to see if there are any significant differences in their habits or experiences.
This study began in July 2014 and concluded in 2017.
Meanwhile the results of the New Zealand multi-centre trial mentioned above were published. It showed a four-fold increased risk in going to sleep supine (on your back) in late pregnancy. Researchers who took part in this trial called for a public-facing campaign letting women know that going to sleep on your side is safer.
Today the MiNESS study has been published. Along with all the other studies it has found that women who went to sleep on their back in late pregnancy were twice as likely to have a stillbirth.