Things that go bump in the night - the new “normal” for baby movements

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Every pregnant woman knows that just as they 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. 

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. It also showed that contrary to advice given to some women, neither a cold drink nor sweet food will prod babies into action.

Through a cross-sectional study of 274 women, with normal pregnancy outcomes, the researchers aimed to describe maternally-perceived foetal movement strength, frequency, and pattern in their third trimester. 59% of women reported feeling movements getting stronger in the previous 2 weeks; strong movements were felt by most women in the evening (73%) and at night-time, including bedtime (79%); 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 hiccough. Hence, it was concluded that it is normal to perceive such symptoms in the third trimester and as pregnancy advances.

“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.”

“Probably the most surprising finding was just how profound an influence time of day was. Only 3.7% of women did not feel strong or moderate movements in the evening,” Bradford said.

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 health care.

“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 foetus has a circadian pattern that involves increased movement in the evening, and this is likely to reflect normal development,” Bradford said.

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.

The take-home message for pregnant women: if your baby usually gets busy at night, rest (if you can) assured.

“It may be an antisocial hour for adults, but it is a social hour for the foetus (and incidentally the newborn), so lack of movement at that time warrants an urgent check-up,” says 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 foetal wellbeing.”