140 bpm · reactive

NST · Antepartum testing

A live look at how your baby is doing.

Nonstress testing gives your care team a real-time view of your baby's heart rate, movement, and uterine activity. Quiet, noninvasive, and reassuring — usually in 20 to 30 minutes.

Visit 20–30 min

Reactive 2+ accels

Results Same day

A live tracing in motion

A continuous look at fetal heart rate alongside uterine activity, just as it appears on the monitor.

180 150 120 90 60

TOCO

100

Live · 3 cm/min JS1 · JS2

FHR · fetal heart rate TOCO · uterine activity

3 CM/MIN · LIVE

What is a nonstress test?

A simple, noninvasive look at fetal well-being.

An NST records your baby's heart rate alongside their movements and any uterine activity. A reassuring pattern, small accelerations with movement, confirms your baby is getting the oxygen they need.

1

Two soft monitors are placed on your belly

One records your baby's heart rate. The second records uterine activity. Both are external, nothing invasive.
2

You sit comfortably for 20–30 minutes

You may be asked to press a marker each time you feel movement. No medication, no ultrasound exposure.
3

Results are reviewed immediately

We look for at least two accelerations with movement in 20 minutes. That's a "reactive" tracing, the goal.
4

Findings go straight to your OB

We communicate results the same day, with a clear next step if any is needed.

20–30 minTypical visit length

2+Accelerations in 20 min = reactive

Same dayResults to your OB

Deeper dive · optional Understanding the science behind the NST

A nonstress test (NST) evaluates how the baby's nervous system and cardiovascular system respond to normal movement and activity inside the uterus. The test is based on an important physiologic principle: a healthy, well-oxygenated baby will usually have temporary increases in heart rate with movement.

The baby's heart rate is controlled by the autonomic nervous system, which includes both the sympathetic ("accelerating") and parasympathetic ("slowing") pathways. As the fetal nervous system matures and receives adequate oxygen, these systems create normal beat-to-beat variability and brief heart rate accelerations. These patterns are reassuring signs of normal neurologic function and oxygen delivery.

During the NST, an external ultrasound monitor measures the fetal heart rate while a second monitor records uterine activity. We evaluate several features of the tracing, including:

Baseline heart rate: the baby's average heart rate over time
Variability: the natural moment-to-moment fluctuation in heart rate caused by a healthy interaction between the fetal brain, nervous system, and heart
Accelerations: temporary increases in heart rate, often triggered by fetal movement or stimulation
Decelerations: drops in heart rate that may sometimes suggest cord compression, contractions, or reduced oxygen reserve

Annotated NST tracing showing baseline, accelerations, variability, and a deceleration on the fetal heart rate channel, with uterine contractions on the lower channel. A blue band marks the normal baseline range of 110–160 bpm. — The features we look for on every tracing — baseline, accelerations, variability, and any decelerations — alongside the lower channel showing uterine activity.

A reactive NST occurs when the baby demonstrates expected accelerations over the monitoring period. This response suggests that the fetal brain, heart, and oxygenation status are functioning normally at that moment in time.

One of the most important aspects of the NST is variability. Moderate variability is considered a strong reassuring sign because it reflects an intact neurologic pathway between the brain and heart. Reduced variability can occur for many benign reasons, including fetal sleep cycles, but it may also be seen when oxygen delivery is impaired.

The NST is called "nonstress" because it observes the baby under normal resting conditions without intentionally creating contractions or physiologic stress. It provides a real-time assessment of fetal well-being and is commonly used in pregnancies requiring closer monitoring, including diabetes, hypertension, fetal growth concerns, decreased fetal movement, or other higher-risk conditions.

Antepartum testing

What's included in a complete picture.

Beyond the NST itself, antepartum monitoring may layer in additional tools depending on your clinical situation. Together they give a more complete read on placental function and fetal well-being.

Nonstress test

Real-time heart rate and uterine activity recording.

Amniotic fluid assessment

Ultrasound measurement of fluid volume around your baby.

Biophysical profile

Five-point ultrasound score, used when more detail is needed.

NST / BPP Reference

When to start antepartum testing, and how often.

A quick reference for the most common indications for nonstress testing and biophysical profile surveillance. Intervals reflect typical practice — final decisions are individualized to the patient and coordinated with the referring OB.

Indication	Typical Start	Frequency
Pregestational diabetes (well controlled) Metabolic	32 weeks	Weeklyor 2×/wk
Pregestational diabetes with vascular disease or poor control Metabolic	28–32 weeks	Twice weekly
Gestational diabetes on medication (A2GDM) Metabolic	32 weeks	Weeklyor 2×/wk
Diet-controlled GDM (A1GDM) Metabolic	No routine testing Unless additional risk factors present	—
Chronic hypertension on medication Hypertensive	32 weeks	Weekly
Chronic HTN with FGR, superimposed preeclampsia, or poor control Hypertensive	28–32 weeks	Twice weeklyOften used
Gestational hypertension or preeclampsia without severe features Hypertensive	At diagnosis Or at viability if expectant management	Twice weeklyUsually
Fetal growth restriction with normal Dopplers Fetal	At diagnosis Often ~28–32 weeks	Weekly NST/BPPPlus Doppler studies
FGR with abnormal Dopplers Fetal	Earlier / intensified Individualized surveillance	2×/week or inpatient
Decreased fetal movement Symptom	At presentation	One-timeOngoing if persistent
Prior stillbirth ≥32 weeks Historical	32 weeks Or 1–2 weeks before prior loss	Weeklyor 2×/wk
Prior stillbirth <32 weeks Historical	Individualized	Individualized
AMA, age ≥40 alone Maternal	36 weeks Consider	Weekly
BMI ≥40 Maternal	34 weeks Consider	Weekly
Oligohydramnios, isolated Fluid	At diagnosis	Weeklyor 2×/wk
Polyhydramnios, moderate or severe Fluid	32–34 weeks	Weekly
Monochorionic twins Twins	32 weeks	Weeklyor 2×/wk
Dichorionic twins, uncomplicated Twins	34 weeks	Weekly
Postdates Gestational	40 weeks	1–2× weekly
Cholestasis of pregnancy Hepatic	At diagnosis When delivery would be acted upon	Weeklyor 2×/wk
Lupus or antiphospholipid syndrome Autoimmune	32 weeks	Weekly
Renal disease or significant cardiac disease Maternal	32 weeks	Weekly

Clinical note — Start times and frequencies reflect commonly accepted practice patterns and align with ACOG / SMFM guidance where applicable. Surveillance should be individualized to the patient's full clinical picture and coordinated with the referring obstetrician. Increase frequency for worsening status, additional risk factors, or new concerning findings.

Coordinated with your OB

Subspecialty monitoring, integrated with your existing care.

NST testing at Advanced Perinatology lives alongside your ultrasound evaluations and consultation visits. Your OB stays informed at every step.

Subspecialty setting

Testing performed in a maternal-fetal medicine office.

Reviewed immediately

Results read in the room, before you leave.

Direct to your OB

Findings communicated to your provider the same day.

Recommended intervals

A clear schedule for follow-up testing if needed.

Coordinated next steps

If more evaluation is needed, we arrange it from here.

If your OB recommends fetal monitoring, we can help coordinate it.

Ultrasound, consultation, and NST testing in one place, so your third-trimester care stays simple and connected.

Talk to our team