Maternal perception of fetal movements: onset and associated factors

Introduction

Fetal movements (FM) can be detected sonographically as early as 7 weeks, while most types of FM patterns occur by 15 weeks of gestation [1, 2]. The first fetal movements felt by pregnant women are called the “quickening” [3]; these first movements are commonly described by women as “butterflies”, “nervous twitches” or a “tumbling” motion [4]. Early in pregnancy, movements are felt occasionally, however, as the fetus grows, usually by the end of the second trimester, the kicks should grow stronger and more frequent [5]. By the end of the second trimester, FM become more distinct and the fetus tends to be most active late at night [6]. Studies have also shown that, by the third trimester, the power and frequency of perceived FM is constant and probably increase close to delivery [7, 8].

However, the exact time when women feel these movements for the first time varies significantly. Women are usually informed that they should expect to feel these movements between 16 and 20 weeks of pregnancy [9]. In their first pregnancy, it is more common to feel the movements in a later gestational age compared to subsequent pregnancies [5]. Additionally, the frequency of FM in normal fetuses may range widely, from 4 up to even 100 per hour [10], while general movements usually involve the trunk, the head and the limbs and occur in a variable order [11]. On the other hand, decreased FM may sometimes cause concerns to the mothers, while psychological parameters may contribute to the perception of FM [12, 13].

To date, there is a gap in the literature regarding the exact onset of maternal FM perception. Therefore, the aim of this study was first to determine the timing of FM perception and second to identify parameters that may affect this timing.

Methods

This was a prospective cohort study conducted between January 2020 and July 2021 by the Third Department of Obstetrics and Gynecology, School of Medicine, Aristotle University of Thessaloniki, Greece. All women with singleton pregnancies attending the first trimester routine scan were prospectively asked to record the time at which they were certain that they felt FM and provide this information at the time of the second trimester scan, at 20⁺⁰–23⁺⁶ weeks, usually scheduled between 21⁺⁰ and 21⁺⁶ weeks. The estimated date of delivery was calculated based on the crown rump length at the first trimester scan. Women who had not felt movements by the time of the routine second trimester scan were again asked to record their first perception and then report it at their next scheduled antenatal scan, at 30–34 weeks. Women that did not attend the scheduled scans or in which fetal abnormalities were identified were excluded.

A research midwife collected all the available data regarding the medical and obstetric history, as well as the timing of first FM perception, which was the main outcome of the study. Secondary outcomes were the associations between this timing and several maternal and fetal factors, including maternal age, body mass index (BMI), gravidity, parity, smoking during pregnancy, previous obstetric history, method of conception, fetal gender, estimated fetal weight at the time of the scan and placental position. All relevant data were routinely and prospectively recorded in a local database (Astraia software gmbh, Munich, Germany).

The women consented for the anonymity of their data and the possible use for research purpose, while no incentives were provided. Following standard policy for observational studies that do not involve any intervention or modification on the routine care of the patients (https://www.hra.nhs.uk/approvals-amendments/what-approvals-do-i-need/), no institutional board review was required for the study [14].

Continuous variables were shown as mean (standard deviation), while all the categorical variables were expressed as n (%). Placental position was dummy coded as a binary variable to estimate the independent effect of each position. Moreover, for some statistical analyses, the variable “onset of perception of FM” was converted into a categorical one, using the mean as a cutoff. The χ² test was used for the univariate analyses of categorical variables, while the independent samples t-test was used to identify differences in continuous variables. Additionally, using a multivariate logistic regression (backward elimination-conditional), we evaluated the association of timing of FM perception with all the possible parameters previously mentioned. Odds ratios (ORs) and 95% confidence intervals (95% CI) were calculated, while significance was set at 5%. All the analyses were performed by SPSS software v.25.0.

Results

Overall, 2,190 women were eligible to participate in the study during the study period; of them, 23 women (1.1%) missed the second trimester scan and 21 (1.0%) were excluded from the study due to fetal abnormalities. From the remaining participants (n=2,146), 2,009 women (93.6%) agreed to participate in the study. The mean maternal age was 32 years (±5), the mean BMI was 23.9 kg/m² (±4.6) and the mean estimated fetal weight (EFW) at the time of the second trimester scan was 478 g (±53). Moreover, 51.7% (n=1,038) were nulliparous and 413 (20.6%) reported previous history of cesarean delivery.

The mean gestational age of first perception of FM was 19 weeks (±1.5). In particular, 1,264 women (62.9%) reported an initial perception of FM at or after 19⁺⁰ weeks. As shown in Figure 1, 25.5% (n=512) perceived FM at 19⁺⁰–19⁺⁶ weeks, while the majority of the participants initially felt FM between 18⁺⁰–20⁺⁶ weeks (73.3%; n=1,473). On the contrary, only a minority of women reported onset of FM at 14⁺⁰–16⁺⁶ weeks (5.5%; n=113, of whom 0.1%; n=3 at 14⁺⁰–14⁺⁶ weeks) or at 22⁺⁰–24⁺⁶ weeks (4.2%; n=86). Of note, 2.2% (n=45) women had not felt movements at the time of the anomaly scan and they reported this information at the next scan at 32 weeks. The sociodemographic and obstetric characteristics of the participants are presented in Tables 1 and 2.

Figure 1:

Gestational age at the onset of maternal perception of fetal movements.

Following multivariate logistic regression analysis, by using the mean “onset of perception of FM” as a dependent categorical variable (cutoff: 19), maternal age, BMI, parity and placental position were identified as independent predictors of the timing of maternal perception of FM. In particular, advancing maternal age (OR: 1.062; 95% CI: 1.040–1.084; p<0.001), high BMI (OR: 1.063; 95% CI: 1.040–1.088; p=0.001), nulliparity (OR: 2.607; 95% CI: 1.876–3.622; p<0.001) and an anterior placental position (OR: 1.918; 95% CI: 1.575–2.336; p<0.001) were associated with delayed first perception of FM in pregnancy. None of the following factors had any effect on the FM: gravidity, planned pregnancy, smoking, method of conception, previous history of cesarean delivery, fetal gender or EFW at the second trimester scan.

In subgroup analyses, multiparous women reported the onset of FM approximately one week earlier on average (18.6±1.4 weeks) compared to nulliparous ones (19.4±1.4 weeks; Mean difference: – MD: 0.843; 95% CI: 0.718–0.968; p<0.001). Similarly, the mean gestational age at the onset of perception of FM was more advanced, at 19.3 weeks (±1.5), in women with anterior placenta, while it was 18.8 weeks (±1.4) for women with non-anterior placenta (MD: −0.505; 95% CI: −0.635 to −0.375; p<0.001) (Table 3). Women at or older than 35 years mentioned FM later than younger ones (19.1±1.5 vs. 19.0±1.5 weeks; MD: −0.158; 95% CI: −0.298 to −0.018; p=0.027). We also found that women with BMI ≥25 kg/m² and those with BMI ≥30 kg/m² reported a later onset of FM than those with BMI <25 kg/m² (19.2±1.5 vs. 18.9±1.5; MD: −0.250; 95% CI: −0.391 to −0.110; p<0.001) and those with BMI <30 kg/m² (19.5±1.5 vs. 19.0±1.5; MD: −0.535; 95% CI: −0.752 to −0.319; p<0.001), respectively.

Additionally, we conducted another subgroup analysis including multiparous women only to check the effect of a previous cesarean delivery on the perception of FM. We found that the mean gestational age at the onset of FM was not significantly different between the group of women with a history of cesarean section (18.6±1.4 weeks) and the group of women with a previous history of vaginal delivery (18.6±1.5 weeks; MD: −0.015; 95% CI: −0.195 to 0.165; p= 0.873).

In another sub-group analysis, we investigated the independent contributors of the onset of maternal perception of FM in the groups of nulliparous and multiparous women, respectively. We found that for nulliparous women, advancing maternal age (OR: 1.064; 95% CI: 1.034–1.095; p<0.001), high BMI (OR: 1.066; 95% CI: 1.029–1.105; p<0.001) and anterior placenta (OR: 2.100; 95% CI: 1.556–2.834; p<0.001) were associated with delayed perception of FM in pregnancy. In the multiparous’ group, advancing maternal age (OR: 1.058; 95% CI: 1.028–1.089; p<0.001) and high BMI (OR: 1.062; 95% CI: 1.031–1.094; p<0.001) delay the onset of FM, while the presence of posterior placenta leads to earlier onset of perception of FM (OR: 0.552; 95% CI: 0.426–0.715; p<0.001).

Discussion

Conclusions

We found that the onset of maternal perception of FM is around 19 weeks, in 73.3% of the cases at 18⁺⁰–20⁺⁶ weeks and that older age, nulliparity, high BMI and an anterior placenta may delay this onset. This information may be useful to health professionals and pregnant women, to provide reassurance especially in primigravidas who often become anxious with regards to FM.