Clinical associations of fetal heart rate accelerations as derived from transabdominal fetal electrocardiograms

To determine the value of quantifying accelerations of the fetal heart rate (FHR), as collected non-invasively during pregnancy, as a proxy for fetal movements.

The study consists of a prospective collection of research material with retrospective analyses of the collected fetal electrocardiograms (ECGs), done in a homogeneous population in a low socioeconomic residential area of Cape Town, South Africa, as part of the Safe Passage Study. Recruitment and follow-up were done from August 2007 to August 2016. Maternal and fetal ECGs were collected non-invasively at various gestational ages, for approximately 30-60 min at a time in 4418 pregnant women. After processing of the signal, the number and duration of accelerations and the area under the acceleration curve of the FHR were calculated and compared with the pulsatility index (PI) of the uterine, umbilical, and middle cerebral arteries, common medical conditions, tobacco, alcohol, marijuana, and methamphetamine use and z-scores of the birthweight (BWZS).

Of the total, 2777, 691, and 3879 women were at gestational ages of 20-24, 28-32 and 34-38 weeks respectively. At 20-24 weeks duration of accelerations was significantly longer in women who used marijuana (p = 0.014) or methamphetamine (p < 0.001) when compared to nonusers. At 28-32 weeks the duration of accelerations was significantly shorter in hypertensive women (p = 0.003) and significantly longer in women who used methamphetamine (p = 0.015). At 34-38 weeks the number of accelerations were significantly less in women who had hypertension ((p = 0.01) or stillbirths (p = 0.028) and the duration significantly shorter in hypertensive women (p = 0.007) and significantly longer in women who used marjuana (p = 0.003) or methamphetamine (p = 0.028). The acceleration area was significantly smaller (p = 0.02) in women who has stillbirths. Duration of accelerations was significantly longer in users of nicotine and alcohol when compared with that of abstainers. Birthweight z-score correlated significantly with number of accelerations (p < 0.01) and the acceleration area (<0.01). There was a significant negative correlation between the number of accelerations (p < 0.01) and acceleration area (p < 0.01) and the PI of the uterine artery at 34-38 weeks.

Calculation of the acceleration parameters of the FHR during pregnancy may provide useful information for evaluating fetal development.