Our study showed that 8.1% of healthy normotensive singleton pregnant women with desirable pregnancy outcomes reported perception of decreased fetal movements. Almost the same rates have been reported in other studies; in an American study of 38,728 pregnancies, 6.6% were examined in the hospitals for concerns of DFM , In Norway maternal concern for DFM is a frequent cause for unscheduled antenatal consultations, occurring in approximately 10% of third-trimester pregnancies . The overall rate of perception of DFM is reported at the range of 4% - 15% in most studies [1, 2]. In our study, some maternal and fetal factors were associated with this perception of DFM, but the three factors that remained independently associated with a perception DFM were maternal employment, the state of not having daily exercise and maternal supine position when counting the fetal movements.
A perception of DFM was reported more often by older mothers and by those who felt the first fetal movements later than the other participants. In our study, this perception was not independent of other maternal factors. In their study of maternal awareness of fetal movements, Saastad et al. indicated that maternal age ≥ 34 years was associated with a low awareness of fetal activity, but this did not affect the risk of being concerned or being examined .
In this study, although the maternal employment rate was low (14.4%), it was an independently associated factor with the maternal perception of DFM. Especially the women who worked more than 8 hours per day felt less fetal movements. Working mothers seem to be at an increased risk of experiencing stress and anxiety which are associated with DFM [3, 12–15]. In their study of stress in working women, Haque & Haleem indicated that working women had higher stress levels and lower serotonin levels , and because serotonin is linked to sustained attention , working mothers with low levels of serotonin could be less alert to fetal movements. It was demonstrated by Olesen & Svare in their review of fetal movements that busy mothers may not perceive as many fetal movements because they are not concentrating on fetal activity, and they often report an inaccurate reduction of fetal movements . An American study documented that working pregnant women have higher catecholamine levels during the work period, and this is known to decrease uterine blood flow . Reduced motor activity is the fetal response to this decreased blood flow . There is an important point that requires attention regarding maternal employment in this study; in the developing countries women employment rate is lower than the developed countries; most women in the developing countries are housewives and are expected to keep their traditional roles and responsibilities at home. Therefore the working women in the developed countries are under higher pressure, due to having too many responsibilities at both work and home and may experience higher stress and anxiety than working women in the developed countries.
In the current, the study mothers who had daily exercise felt more fetal movements than the non-exercising mothers. Other studies showed a decrease in fetal breathing and body movements in response to heavy maternal exercise . Exercise seems to have different effects on the maternal perception of fetal movements depending on its regularity, duration and severity. Regular mild to moderate exercise seems to improve the maternal perception of fetal movements through different mechanisms affecting both the mothers and the fetuses. Exercise results in increased serum cortisol, hippocampal dopamine and serotonin levels, and these changes lead to increased mood and mental alertness [17, 20], which can improve the maternal perception of fetal movements. A Canadian study showed that pregnant women who exercise during pregnancy experience significant decreases in depression, anger, tension, fatigue and anxiety , the factors which have been shown to be associated with decreased perception of fetal movements [12, 14, 15].
From the fetal perspectives, elevated maternal cortisol has been linked to increased fetal movements. A study by DiPietro et al. showed that maternal cortisol is significantly associated with fetal motor amplitude and the total time spent moving . This could be due to the effect of cortisol on the developing brain; glucocorticoid exposure during the fetal period has organizational effects on the developing brain, including the modification of synaptogenesis, neurotransmitter function, and glucocorticoid receptor expression with long-term implications for structure and function . In the study by Ellman et al., higher maternal cortisol levels were associated with advanced neonatal neuromuscular maturation . Maternal exercise improves fetal growth and placental vascularization and increases serum placental growth factor [24, 25], which might affect fetal movements .
We were unable to find studies examining the effect of mother’s different positions on her perception of fetal movements. This study showed that when mothers are in the supine position, they feel less fetal movements. When a pregnant woman is in the supine position, the inferior vena cava is compressed by the gravid uterus, resulting in a decrease in cardiac output, stroke volume and ejection fraction. These changes lead to an increased heart rate , more suppressed vagal activity and enhanced sympathetic activity . Approximately 10 – 12% of the catecholamines are transferred to the fetal circulation, which may contribute to fetal vasoconstriction and the development of fetal hypoxemia and hypoxia . The fetal responses to maternal sympathetic activation and hypoxemia include increased a variability of the heart rate concomitant with the suppression of motor activity .
We did not find any associations between the perception of DFM and the AFI. This is consistent with a study by Almli et al., which did not find a significant association between the amniotic fluid volume and leg movements per minute . Some studies have reported that decreased amniotic fluid volume is associated with DFM . A review of DFM indicated that oligohydramnios and polyhydramnios have been shown to be associated with DFM . Several factors can account for these differences, including interobserver and intraobserver variations , gestational age at the examinations, sample size and the percentage of abnormal AFI in these studies.
Studies with conflicting results have assessed the associations of the placental site and the perception of DFM. In the present study, no significant association was found between the perception of DFM with the placental location, and similar results were reported by several smaller studies (a total of 94 women) , a British study of 182 patients reported an association of DFM with an anterior placenta . In another study of 284 women, an anterior placenta was associated with a reduced perception of fetal movements only in some gestational ages and not throughout the entire pregnancy . These conflicting results are mainly due to the small sample sizes, different gestational ages and lack of consistent definitions .
This study is among the few studies to search for an association between DFM and fetal presentation. In our study, the mothers of fetuses with transverse presentation had a higher percentage for the perception of DFM, but this difference was not statistically significant. A Canadian study of 28 fetuses indicated that there are no differences in the spontaneous fetal heart rate, body or breathing movements in fetuses in the breech position compared with the cephalic position, but fetuses in the breech position showed atypical movement responses to vibroacoustic and airborne sound stimuli . Sherer et al. in their study of 465 pregnant women, reported that the fetal presentation was not significantly different between the patients based on the score of fetal movements .
One of the main limitations of the study was the compliance of the participants; due to the limited compliance of the participants we could not ask them to count the fetal movements till the end of pregnancy to see if any changes happen in maternal perception of fetal movements over time. Another limitation of the study was the small number of participants who had some of the studied characteristics, for instance we could not have an accurate assessment of the association of maternal perception of DFM with oligohydramnios.