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A normal nonstress test will show a baseline fetal heart rate between 110 and 160 beats per minute with moderate variability (5- to 25-interbeat variability) and 2 qualifying accelerations in 20 minutes with no decelerations. "Reactive" is defined as the presence of two or more fetal heart rate accelerations within a 20-minute period. Each ...
A contraction stress test (CST) is performed near the end of pregnancy (34 weeks' gestation) to determine how well the fetus will cope with the contractions of childbirth. The aim is to induce contractions and monitor the fetus to check for heart rate abnormalities using a cardiotocograph. A CST is one type of antenatal fetal surveillance ...
Cardiac activity is visible beginning at approximately 5 weeks of pregnancy. The human heart begins beating at a rate near the mother's, about 75-80 beats per minute (BPM). The embryonic heart rate (EHR) then accelerates linearly for the first month of beating, peaking at 165-185 BPM during the early 7th week, (early 9th week after the LMP).
The heart rate increases, but generally not above 100 beats/ minute. Total systematic vascular resistance decreases by 20% secondary to the vasodilatory effect of progesterone. Overall, the systolic and diastolic blood pressure drops 10–15 mm Hg in the first trimester and then returns to baseline in the second half of pregnancy. [ 6 ]
Normal (2 points) Abnormal (0 points) NST/Reactive FHR At least two accelerations in 20 minutes Less than two accelerations to satisfy the test in 20 minutes US: Fetal breathing movements At least one episode of > 30s or >20s [3] in 30 minutes None or less than 30s or 20s [3] US: Fetal activity / gross body movements
A Zigzag pattern of fetal heart rate (FHR) is defined as FHR baseline amplitude changes of more than 25 beats per minute (bpm) with a minimum duration of 2 minutes and maximum of 30 minutes. [19] However, according to another study, even a >1 min duration of the zigzag pattern is associated with an increased risk of adverse neonatal outcomes. [21]
The sex of the fetus may be discerned by ultrasound as early as 11 weeks' gestation. The accuracy is relatively imprecise when attempted early. [15] [16] [17] After 13 weeks' gestation, a high accuracy of between 99% and 100% is possible if the fetus does not display intersex external characteristics. [18]
The term is also sometimes used to designate late decelerations of fetal heart rate as measured by cardiotocography or an NST, even if there is no other evidence of reduced blood flow to the placenta, normal uterine blood flow rate being 600mL/min.