Читать книгу Protocols for High-Risk Pregnancies - Группа авторов - Страница 89

In general, the American College of Obstetricians and Gynecologists has recommended antepartum testing for specific maternal and fetal conditions. Such testing is intended to reduce the risk of stillbirth and has been generally accepted. However, it should be noted that the benefit of fetal surveillance testing of whatever form is based solely on observational studies which allowed clinical intervention. These studies have consistently suggested that stillbirth rates in tested populations of at‐risk patients are significantly lower than those in either untested low‐risk patients or similarly risked pregnancies managed without fetal surveillance testing.

There are a number of conditions associated with an increased risk of stillbirth for which fetal surveillance testing has been used routinely. Generally speaking, fetal surveillance testing is indicated in pregnancies complicated by conditions for which the stillbirth rate exceeds 0.8 per 1000 (which is the false‐negative rate for either a normal biophysical profile or a normal modified biophysical profile) and which also have an increased relative risk for stillbirth of more than twofold when compared with pregnancies without such conditions. However, the mechanisms responsible for the increased risk of stillbirth for a specific abnormal pregnancy condition are generally unknown. Further, the lack of prospective studies establishing a benefit of reduced stillbirth with fetal testing in the management of such complicated pregnancies makes it challenging to establish a specific list of all indications for which antepartum testing is indicated. This also applies to the timing of testing initiation during pregnancy and frequency of testing.

Newer examples of concerns for an increased risk of stillbirth but for which fetal surveillance testing has not previously been routinely recommended include conditions such as maternal obesity, advanced maternal age, pregnancy resulting from assisted reproductive techniques or pregnancies in women self‐reported as being black. While each of these conditions is a weak but potentially independent stillbirth risk factor, they are common and may present specific logistical, sociological, and systemic challenges if they are included as indications for antenatal fetal testing. Indeed, all indications for antepartum fetal testing should be considered as somewhat relative and may vary in significance among different providers. However, in general, the conditions for which fetal testing are recommended are listed below.

 Maternal conditions: pregestational diabetes mellitus, hypertension, systemic lupus erythematosus, chronic renal disease, antiphospholipid syndrome, poorly controlled hyperthyroidism, hemoglobinopathy (such as sickle cell anemia, sickle‐hemoglobin C or sickle‐thalassemia disease), and cyanotic heart disease.

 Pregnancy‐related conditions: preeclampsia, gestational hypertension, decreased fetal movement, oligohydramnios (deepest vertical pocket less than 2.0 cm), moderate or severe polyhydramnios (deepest vertical pocket 12.0 cm or greater or an AFI greater than 30.0 cm), intrauterine growth restriction, pregnancy at or beyond 41 completed weeks of gestation, isoimmunization, history of stillbirth, dichorionic twins with significant growth discrepancy or beyond 36 weeks’ gestation, monochorionic/diamniotic twins, premature rupture of membranes, and third‐trimester uterine bleeding.

 Potential other indications: maternal age of 35 years or greater, obesity, maternal black race, suspected or confirmed fetal structural or genetic abnormalities, pregnancies conceived by in vitro fertilization, intrahepatic cholestasis of pregnancy, abnormal first‐ or second‐trimester serum analytes used in genetic risk assessment, abnormal umbilical cord findings such as vasa previa, single umbilical artery or velamentous cord insertion.

The following general factors apply to testing.

 Testing is generally initiated at 32–34 weeks for most patients; at 40 weeks for diet‐controlled gestational diabetics. However, it may begin as early as 26 weeks of gestation in pregnancies with multiple risk factors or when fetal compromise is suspected. The fetal heart rate reactivity may be diminished due to early gestational age and not necessarily reflect fetal compromise. Back‐up testing should be used whenever primary surveillance is of any concern.

 Doppler velocimetry of the umbilical artery may be performed weekly in pregnancies complicated with suspected intrauterine growth restriction. This ultrasound procedure is generally performed in addition to biweekly nonstress testing.

 A normal fetal surveillance heart rate test is typically repeated on a twice‐weekly basis.

 Test should be immediately repeated in the event of significant deterioration in the clinical status regardless of the time elapsed since the last test. Intervention with delivery is always a clinical decision and may be indicated with either normal or abnormal testing depending upon the clinical circumstances.