Open Access Research article

Wavelet principal component analysis of fetal movement counting data preceding hospital examinations due to decreased fetal movement: a prospective cohort study

Brita Askeland Winje1*, Jo Røislien12, Eli Saastad1, Jorid Eide1, Christopher Finne Riley3, Babill Stray-Pedersen45 and J Frederik Frøen1

Author Affiliations

1 Division of Epidemiology, Norwegian Institute of Public Health, PO Box 4404, Nydalen, 0403, Oslo, Norway

2 Department of Biostatistics, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway

3 Department of Obstetrics and Gynecology, Østfold Hospital Trust, Fredrikstad, Norway

4 Institute of Clinical Medicine, University of Oslo, Oslo, Norway

5 Women and Children’s Division, Oslo University Hospital Rikshospitalet, Oslo, Norway

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BMC Pregnancy and Childbirth 2013, 13:172  doi:10.1186/1471-2393-13-172

Published: 5 September 2013

Abstract

Background

Fetal movement (FM) counting is a simple and widely used method of assessing fetal well-being. However, little is known about what women perceive as decreased fetal movement (DFM) and how maternally perceived DFM is reflected in FM charts.

Methods

We analyzed FM counting data from 148 DFM events occurring in 137 pregnancies. The women counted FM daily from pregnancy week 24 until birth using a modified count-to-ten procedure. Common temporal patterns for the two weeks preceding hospital examination due to DFM were extracted from the FM charts using wavelet principal component analysis; a statistical methodology particularly developed for modeling temporal data with sudden changes, i.e. spikes that are frequently found in FM data. The association of the extracted temporal patterns with fetal complications was assessed by including the individuals’ scores on the wavelet principal components as explanatory variables in multivariable logistic regression analyses for two outcome measures: (i) complications identified during DFM-related consultations (n = 148) and (ii) fetal compromise at the time of consultation (including relevant information about birth outcome and placental pathology). The latter outcome variable was restricted to the DFM events occurring within 21 days before birth (n = 76).

Results

Analyzing the 148 and 76 DFM events, the first three main temporal FM counting patterns explained 87.2% and 87.4%, respectively, of all temporal variation in the FM charts. These three temporal patterns represented overall counting times, sudden spikes around the time of DFM events, and an inverted U-shaped pattern, explaining 75.3%, 8.6%, and 3.3% and 72.5%, 9.6%, and 5.3% of variation in the total cohort and subsample, respectively. Neither of the temporal patterns was significantly associated with the two outcome measures.

Conclusions

Acknowledging that sudden, large changes in fetal activity may be underreported in FM charts, our study showed that the temporal FM counting patterns in the two weeks preceding DFM-related consultation contributed little to identify clinically important changes in perceived FM. It thus provides insufficient information for giving detailed advice to women on when to contact health care providers. The importance of qualitative features of maternally perceived DFM should be further explored.

Keywords:
Decreased fetal movement; Fetal movement counting; Fetal movement chart; Kick chart; Kick counting; Fetal monitoring; Fetal compromise; Wavelet principal component analysis