Practice Guidelines

ACOG Guidelines on Antepartum Fetal Surveillance

Am Fam Doc. 2000 Sep one;62(five):1184-1188.

The Committee on Do Bulletins–Obstetrics of the American College of Obstetricians and Gynecologists (ACOG) has developed clinical direction guidelines on antepartum fetal surveillance. Co-ordinate to the committee, the goal of antepartum fetal surveillance is to prevent fetal death. The techniques of antepartum fetal surveillance, which are based on the assessment of fetal heart rate patterns, have been in clinical utilise for well-nigh 30 years. These guidelines, which replace Technical Bulletin No. 188 issued in Jan 1994, announced in the Oct 1999 result of Obstetrics and Gynecology.

Techniques of Antepartum Fetal Surveillance

Several techniques for antepartum fetal surveillance currently in utilize are discussed in the ACOG bulletin. These include fetal movement assessment, nonstress test, contraction stress test, fetal biophysical profile, modified biophysical contour and umbilical avenue Doppler velocimetry.

FETAL Motion Assessment

Fetal move assessment occurs when the mother perceives a diminution in fetal movement. The mother counts fetal "kicks" as a means of antepartum fetal surveillance. The optimal number of movements and the ideal elapsing for counting movements have non been adamant; however, numerous protocols have been reported and appear to be acceptable.

CONTRACTION STRESS TEST

The wrinkle stress exam is based on the response of the fetal eye rate to uterine contractions. It is believed that fetal oxygenation will be transiently worsened by uterine contractions. In the fetus with suboptimal oxygenation, the resulting intermittent worsening in oxygenation will, in turn, lead to the fetal centre charge per unit blueprint of late decelerations. Uterine contractions also may provoke or accentuate a design of variable decelerations acquired by fetal umbilical cord compression, which in some cases is associated with oligohydramnios.

The wrinkle stress examination is interpreted by the presence or absence of tardily fetal heart charge per unit decelerations, which are divers equally decelerations that achieve their nadir later the peak of the wrinkle and that usually persist across the stop of the contraction. The results of the wrinkle stress examination are categorized in the ACOG bulletin as follows:

  • Negative. No late or meaning variable decelerations.

  • Positive. Late decelerations following 50 pct or more of contractions (fifty-fifty if the contraction frequency is fewer than three in 10 minutes).

  • Equivocal-suspicious. Intermittent late decelerations or meaning variable decelerations.

  • Equivocal-hyperstimulatory. Fetal center rate decelerations that occur in the presence of contractions that are more frequent than every two minutes or last longer than ninety seconds.

  • Unsatisfactory. Fewer than three contractions in ten minutes or a tracing that is not interpretable.

Relative contraindications to the contraction stress test commonly include conditions that are associated with an increased chance of preterm labor and commitment, uterine rupture or uterine haemorrhage. Co-ordinate to ACOG, these weather condition include the following:

  • Preterm labor or certain patients at loftier hazard of preterm labor.

  • Preterm membrane rupture.

  • History of extensive uterine surgery or archetype cesarean delivery.

  • Known placenta previa.

NONSTRESS Test

In the nonstress test, the middle rate of the fetus that is not acidotic or neurologically depressed will temporarily accelerate with fetal movement. Eye rate reactivity is believed to be a skillful indicator of normal fetal autonomic part. Loss of reactivity is normally associated with a fetal sleep cycle but may issue from any crusade of central nervous organisation depression, including fetal acidosis.

Results of nonstress tests are classified as reactive or nonreactive. Various definitions of reactivity have been used. Nearly ordinarily, the nonstress exam is considered reactive, or normal, if there are two or more fetal heart rate accelerations within a 20-infinitesimal period, with or without fetal movement discernible by the adult female, co-ordinate to ACOG. The nonreactive stress test lacks sufficient fetal middle charge per unit accelerations over a 40-minute menstruum. The nonstress test of the neurologically salubrious preterm fetus is frequently nonreactive—from 24 to 28 weeks of gestation, up to 50 percent of nonstress tests may not exist reactive, and from 28 to 32 weeks of gestation, 15 percent of nonstress tests are not reactive.

BIOPHYSICAL PROFILE

The biophysical contour discussed in the ACOG bulletin is a nonstress test plus four observations made by real-time ultrasonography. The five components of the biophysical profile are as follows: (ane) nonstress test; (ii) fetal breathing movements (one or more episodes of rhythmic fetal breathing movements of thirty seconds or more inside thirty minutes); (3) fetal movement (three or more detached body or limb movements inside 30 minutes); (iv) fetal tone (i or more episodes of extension of a fetal extremity with return to flexion, or opening or closing of a hand; and (5) determination of the amniotic fluid volume (a single vertical pocket of amniotic fluid exceeding two cm is considered show of acceptable amniotic fluid).

Each of the components is given a score of 2 (normal or nowadays every bit defined previously) or 0 (abnormal, absent or bereft). A composite score of 8 or 10 is normal, a score of half dozen is equivocal and a score of 4 or less is abnormal. In the presence of oligohydramnios, farther evaluation is warranted regardless of the composite score.

MODIFIED BIOPHYSICAL PROFILE

During the late 2nd or third trimester, amniotic fluid reflects fetal urine production. Placental dysfunction may cause diminished fetal renal perfusion, which can lead to oligohydramnios. Therefore, assessment of amniotic fluid book can be used to evaluate long-term uteroplacental function. This led to the development of the modified biophysical profile.

The modified biophysical contour combines the not-stress test with the amniotic fluid index, which is the sum of measurements of the deepest cord-free amniotic fluid pocket in each of the abdominal quadrants, as an indicator of long-term part of the placenta. An amniotic fluid index of more than 5 cm is thought to exist an acceptable book of amniotic fluid. The modified biophysical contour is considered normal if the nonstress test is reactive and the amniotic fluid alphabetize is greater than five cm and aberrant if the nonstress exam is nonreactive or the amniotic fluid index is five cm or less.

UMBILICAL Avenue DOPPLER VELOCIMETRY

Doppler ultrasonography is used to assess the hemodynamic components of vascular impedence. Umbilical artery Doppler flow velocimetry has been adapted as a fetal surveillance technique because information technology is believed that flow velocity waveforms in the umbilical avenue of fetuses with normal growth differ from those of fetuses with growth restriction. The umbilical flow velocity waveform of a normally growing fetus has high-velocity diastolic period, while in cases of intrauterine growth restriction, the umbilical artery diastolic menses is macerated. With extreme intrauterine growth restriction, the flow may be absent or even reversed. There is a loftier perinatal bloodshed rate among such pregnancies.

Indications for Antepartum Fetal Surveillance

The results of antepartum fetal surveillance have non definitively demonstrated improved perinatal outcome. Therefore, all indications for antepartum testing should be considered somewhat relative. Usually, antepartum fetal surveillance is used in pregnancies with a high hazard of antepartum fetal death. Some of the conditions in which testing is appropriate include the following:

  • Maternal weather condition: antiphospholipid syndrome, poorly controlled hyperthyroidism, hemoglobinopathies such as hemoglobin SS, SC or S-thalassemia, cyanotic heart disease, systemic lupus erythematosus, chronic renal disease, blazon 1 diabetes mellitus and hypertensive disorders.

  • Pregnancy-related weather: pregnancy-induced hypertension, decreased fetal movement, oligohydramnios, polyhydramnios, intrauterine growth brake, mail-term pregnancy, moderate to severe isoimmunization, previous fetal demise (unexplained or recurrent risk) and multiple gestation with pregnant growth discrepancy.

Recommendations

The following ACOG recommendations are based on limited or inconsistent scientific evidence (Level B):

  • Women at high risk for stillbirth should undergo antepartum fetal surveillance using the nonstress examination, wrinkle stress test, biophysical profile or modified biophysical contour.

  • Initiation of testing at 32 to 34 weeks of gestation is appropriate for most pregnancies that are at increased risk of stillbirth. In pregnancies with multiple or particularly worrisome high-gamble atmospheric condition, testing may be initiated as early as 26 to 28 weeks of gestation.

  • When the clinical status that prompted testing persists, a reassuring exam should be repeated weekly or, depending on the exam used and the presence of certain high-run a risk conditions, twice weekly until delivery. Any pregnant deterioration in fetal activity requires fetal reevaluation, regardless of the amount of time that has elapsed since the terminal test.

  • An abnormal nonstress examination or modified biophysical profile ordinarily should exist farther evaluated by a contraction stress exam or a full biophysical contour. Subsequent management should then be predicated on the results of the contraction stress test or biophysical profile, the gestational age, the degree of oligohydramnios (if assessed) and the maternal condition.

  • Oligohydramnios, defined as no ultrasonographically measurable vertical pocket of amniotic fluid greater than 2 cm or an amniotic fluid index of 5 cm or less, requires (depending on the degree of oligohydramnios, the gestational age and the maternal clinical condition) commitment, or close maternal or fetal surveillance.

  • In the absence of obstetric contraindications, delivery of the fetus with an abnormal exam result often may be attempted past induction of labor with continuous monitoring of the fetal eye charge per unit and contractions. If repetitive late decelerations are observed, cesarean delivery mostly is indicated.

  • Recent, normal antepartum fetal test results should non preclude the use of intrapartum fetal monitoring.

  • Umbilical artery Doppler velocimetry seems to do good but pregnancies complicated by intrauterine growth restriction. If used in this setting, decisions regarding timing of delivery should be made using a combination of data from the Doppler ultrasonography and other tests of fetal well-being, along with careful monitoring of maternal status.

  • Heart cerebral avenue Doppler velocimetry should be considered an investigational approach to antepartum fetal surveillance.

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