Continuous variables were presented as means and standard deviations and were compared by using Student's independent samples t-tests. The sex was established at the time of birth.ĭescriptive statistics and univariate analyses were used as appropriate for continuous or categorical variables.
The fetal heart rate was obtained using spectral Doppler ultrasound for 4–5 heart beats while keeping the thermal index for soft tissues and bone as low as possible (<1) in accordance with the As Low As Reasonably Achievable (ALARA) principle. The General Electric Voluson E8 machine was equipped with 2.0–5.0 MHz abdominal and 4.0–9.0 MHz vaginal transducers. The Aloka Alpha 10 machine was equipped with 3.0–7.5 MHz abdominal and 3.5–7.5 MHz vaginal transducers. The Acuson Sequoia machine was equipped with 4.0–8.0 MHz abdominal and vaginal transducers. US examinations were performed using Acuson Sequoia (Mountain View, CA), Aloka Alpha 10 (Tokyo, Japan) and General Electric Voluson E8 (Rancho Cordova, CA) machines. The Institutional Review Board of the Charleston Area Medical Center approved the study. The exclusion criteria were: maternal bradycardia or tachycardia, maternal thyroid disease, maternal cardiac arrhythmias, maternal use of beta blocker agents, maternal anxiety disorder, maternal fever, spontaneous abortion, stillbirths, ambiguous genitalia at birth, fetal malformations, fetal cardiac arrhythmias and fetal chromosomal abnormalities. The inclusion criteria were: singleton pregnancies with documented FHR that delivered at our hospital and had pregnancy dating by a last menstrual period (LMP) and a confirmatory crown rump length (CRL) measurement or had an uncertain LMP and were dated by the initial CRL.
The medical records and USs of these patients were retrospectively reviewed. This is a study of births at Women and Children's Hospital from Januto Apin which USs were performed between 8 and 13 weeks of gestation at the hospital's Perinatal Diagnostic Center.
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