References:
- Dr. RPS Maternal and Newborn Care: A Comprehensive Guide and Source Book for Teaching and Learning, 2nd Edition, ISBN 978-971-98-2265-3, by Rosalinda Parado Salustiano (Ch. 6, pp. 117-195)
Ultrasonography
An ultrasound is a non-invasive diagnostic procedure utilizing high-frequency sound waves to detect intrabody structures. It is advantageous in that it is accessible, does not ionizing radiation, and excellently depicts female genital anatomy. It is the imaging of choice in the initial evaluation of gynecologic emergencies. It may be used to:
- Confirm pregnancy in early gestation.
- Obtain fetal parameters: viability, growth, number, position, presentation, structural abnormalities, heart tones, and age of gestation via biparietal diameter of the fetal head (most accurate from 12 to 24 weeks, 9.5 cm in a mature fetus)
- Detect placental location or abnormality, such as placenta previa and H-mole.
- Assist in other procedures, such as amniocentesis.
Procedure
- Drink 1 quart of water 2 hours before the procedure.
- Do not void prior to the procedure.
- Prepare transmission gel to be spread over the abdomen.
- Provide psychological support to both mother and father. Explain the reason, risks, benefits, and preparations required for the procedure. Explain that no known risk to the mother and fetus is associated with infrequent exposure to high-frequency sound waves.
- Encourage verbalization of fears and concerns. Explain that the procedure is noninvasive, safe, requires no confinement, has no need for dye or contrast, and takes a short period (about 30 minutes) to accomplish.
Nonstress Test (NST)
A non-stress test observes fetal heart tones (FHT) in relation to fetal movements as a test of fetal well-being. In a normal fetus, FHT increases with fetal movements. The following findings may be observed:
- Normal; Reactive Nonstress Test: the FHT accelerates greater than 15 BPM above baseline, lasting 15 or more seconds in a 10 to 20 minute period with fetal movement. If found in a high-risk client, the pregnancy may continue.
- Abnormal; Nonreactive Nonstress Test: FHR does not accelerate with fetal movement. If found in a high-risk client, further testing is performed, such as a Biophysical Profile.
Procedure
The mother is positioned semi-Fowler’s or left lateral position slightly turned to the left.
- Check her blood pressure
- Explain the procedure: its duration is 30 to 60 minutes, and requires no hospitalization; this can be done on an ambulatory basis. The mother will need to activate the “mark button” for each fetal movement felt.
- Prepare external electronic FHT monitor with an ultrasound transducer and tocodynamometer to trace fetal activity and/or uterine activity.
Oxytocin Challenge Test (OCT)/Contraction Stress Test (CST)
Contractions are induced to observe the response of the fetus as a test of feto-placental well-being. A normal finding must show three contractions within 10 minutes each showing no late decelerations. Late decelerations are decelerations in FHT even after the peak of contraction, and lasts even after the contraction has ended. This indicates that the fetus is not receiving a proper amount of oxygen.
Procedure
The mother is positioned semi-Fowler’s or left lateral position.
- Check her blood pressure 15 minutes before and prior to the exam.
- Explain the procedure: its duration is 1 to 3 hours. The mother receives oxytocin in an increasing dosage until three contractions is observed in 10 minutes. This may be done on an outpatient basis.
- This also requires an external electronic FHT monitor with an ultrasound transducer and tocodynamometer to detect uterine activity.
Nipple Stimulation Contraction Test
The breasts are stimulated with the rolling of nipples or warm towel application. This stimulates the posterior pituitary gland to secrete oxytocin, contracting the uterine musculature (and breast tubules)./ In this test, the fetal response to uterine contractions is tested. The monitoring and interpretations are the same as in the oxytocin contraction test.
Biophysical Profile
A scoring system that utilizes ultrasound assessments to determine the presence of chronic asphyxia. A score of 10 to 8 is normal (low risk), 4 to 6 is suspected for chronic asphyxia, and a score of 0 to 2 is a high risk for chronic asphyxia.
| Biophysical Variable | Normal (2) | Abnormal (0) |
|---|---|---|
| Fetal Breathing Movements | Grater than or equal to one episode of 30 seconds or more of fetal breathing movement in 30 minutes | Absence of 30 seconds or longer of fetal breathing movement in 30 minutes |
| Gross Fetal Movement | Three or more discreet movements of the body or any limb in 30 minutes | Two or fewer discreet movements of the body or a limb in 30 minutes |
| Fetal Tone | One or more episodes of extensions and flexion of the fetal limb(s) or trunk Opening and closing of the hand is considered normal | Either slow extension with return to partial flexion, movement of the limb in full extension, or absent fetal movement |
| Reactive Fetal Heart Rate | Two or more episodes of accelerations for 15 BPM or more lasting for 15 seconds or longer in 20 minutes; associated with fetal movement | Less than two episodes of acceleration of the fetal heart rate or acceleration of less than 15 BPM in 20 minutes |
| Qualitative Amniotic Fluid Volume | One pocket or more of fluid measuring 1 cm or more in two peripendicular planes | Either no pockets or a pocket of 1 cm or less in two perpendicular planes |
Amniocentesis
The amniotic sac is entered to aspirate amniotic fluid for a variety of diagnostic exams to determine fetal well-being. In a fetus at 15 to 18 weeks of gestation, up to 30 mL of amniotic fluid is aspirated. Many methods for analysis can be done for a variety of indications:
- Foam Stability Test/Shake Test: the most common test to determine fetal lung maturity, finding the L/S ratio to be 2:1 in mature lungs.
- Age of Gestation (AOG) can be found with creatinine levels (2.0 mg in 36 weeks, more onwards) or a nile blue stain (staining lipid cells)— 20% of aspirated cells should stain orange, indicating a fetal weight of at least 2,500 grams.
- Alpha-Fetoprotein (AFP): can be measured which, if elevated, can indicate the presence of a neural defect (spina bifida, tracheoesophageal atresia).
- Genetic disorders and sex-linked disorders can be checked with chromosomal studies and sex chromosome determination.
- Rh Incompatibility results in high levels of bilirubin (from isoimmunization). The mother is evaluated for intrauterine transfusion or delivery.
- Inborn errors of metabolism can be determined through biochemical analysis of fetal cell enzymes.
- Fetal distress may be determined with the presence of meconium while in cephalic presentation (not significant when breech).
Procedure
- Secure informed consent. Inform the mother of the major risks of the procedure: trauma to the fetus, placenta, umbilical cord, and maternal surface; infection; abortion; preterm labor.
- Prepare for ultrasonography to locate the placenta and provide visualization during a blind procedure.
- Void prior to the procedure in order to prevent injuring the distended bladder with a needle. Similar to a normal ultrasound, the mother drinks 1 quart of water 2 hours before the procedure.
- Prepare equipment: g 20–22 3” to 6” needle and local anesthesia for the abdomen.
- Provide psychological support: inform the patient of the details of the procedure: up to 30 mL of amniotic fluid is aspirated at 15 to 18 weeks of gestation.
- Aftercare: monitor the client for 30 to 60 minutes. Observe for side effects such as vaginal discharge, increasing uterine/fetal activity, and fever or chills.
Others
- X-ray, specifically lateral pelvimetry, is used for the determination of pelvic size and shape, indicated for those with suspected cephalopelvic disproportion, a history of injury or disease of the pelvis and spine, previous difficult deliveries, and cases of maternal deformities or limps.
- Special Estriol Determination is a measurement of feto-placental well-being by analyzing serum or 24-hour urine (more common) samples for estriol.
- Normally, estriol rises by 12 to 50 mg/day at term.
- Abnormally, a sudden drop in estriol (more than half of previous levels) indicate fetal distress. Persistence of this low level means fetal well-being is compromised.
- Chorionic Villi Sampling (CVS) is the earliest test done to test fetal cells. This is done via a catheter passed through the cervix.
- Percutaneous Umbilical Blood Sampling (PUBS) is used in the second and third trimesters, aspirating and testing cord blood. Ultrasound is used to locate the umbilical cord.