Things that go bump in the night: new ‘normal’ for baby movements
13 June 2019
You hear it all the time: just as pregnant women are settling down for the evening, their babies kick into party mode.
Now a University of Auckland-led study shows it is entirely normal in late pregnancy for babies to be more active in the evening and bedtime, and that babies’ movements tend to keep getting stronger even as they come to term.
It also showed that – contrary to advice given to some women – neither a cold drink nor sweet food will prod babies into action.
The study of pregnant women’s own observations, published in scientific journal PLOS ONE, debunks some myths about babies’ movements during pregnancy and gives much-needed, clear guidance to women and their health professionals about what is normal.
“Pregnant women are often advised to keep an eye on their baby’s movement pattern and report any decrease in movements,” says lead author, Billie Bradford, a PhD student in the University’s Faculty of Medical and Health Sciences and a practicing midwife.
“But, even though there is a link between decreased movements and stillbirth, most women who report a drop in activity will go on to have a healthy baby. The problem is, there is limited evidence about what normal patterns of movement look like, and around the world women are getting mixed advice. We thought this would be useful information, particularly for first-time mothers who are getting to know what a normal pattern is for them.”
It may be an antisocial hour for adults, but it is a social hour for the fetus... so lack of movement at that time warrants an urgent check-up
The research team interviewed pregnant women in their third trimester (after 28 weeks of pregnancy) about the nature and frequency of their babies’ movements, and analysed the responses of those who gave birth to a live, well-grown baby after 37 weeks (‘at term’). The women were from seven regions of Aotearoa New Zealand and ethnically representative.
The main findings were:
- The majority (59 percent) of women reported feeling movements getting stronger in the previous two weeks
- Strong movements were felt by most women in the evening (73 percent) and at night-time including bedtime (79 percent)
- Women were more likely to perceive moderate or strong movements when sitting quietly compared with other activities, such as having a cold drink or eating
- Almost all women reported feeling their babies hiccup
“Probably the most surprising finding was just how profound an influence time of day was - only 3.7 percent of women did not feel strong or moderate movements in the evening,” says Mrs Bradford.
“Pregnant women have always reported more baby movements in the evening. This is often put down to distraction and being busy during the day, but that may not be the whole story. A number of ultrasound and animal studies have shown that the fetus has a circadian pattern that involves increased movement in the evening, and this is likely to reflect normal development.”
There is a growing appreciation of how circadian patterns may be important in health, and researchers are investigating how timing of assessments and therapies can improve outcomes across many areas of healthcare, she says.
Senior author, Professor Lesley McCowan, says, “It’s clear that the pattern of movement is more consistent across pregnant women than the number of kicks – which varies widely between women, from four to 100 an hour.”
Professor McCowan is Head of the University’s Department of Obstetrics and Gynaecology and was recently recognised for her outstanding pregnancy research.
The take-home message for pregnant women: if your baby usually gets busy at night, rest (if you can) assured. If you’re concerned that your baby is moving less often, less strongly or not moving in the evening as they normally would, don’t wait until the next day for a check-up.
“It may be an antisocial hour for adults, but it is a social hour for the fetus (and incidentally the newborn), so lack of movement at that time warrants an urgent check-up,” says Mrs Bradford.
“As a midwife, I find it especially gratifying to see evidence emerge that pregnant women’s own knowledge of their baby provides valuable insights into fetal wellbeing.”
The team is now working on developing a tool for assessing the quality of fetal movements that includes circadian pattern, and investigating fetal movement patterns in women who have high BMI.
The study’s other authors were from the University of Auckland and the Liggins Institute. Funding came from The Health Research Council of New Zealand, Cure Kids, Mercia Barnes Trust, and Nurture Foundation.
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