Current standard of care in obstetrics considers the fetus as a patient distinct and separate from the mother. Ethically and legally, the obstetrician or nurse midwife must take into account the fetal well-being when making decisions concerning a pregnancy. In particular, during the third trimester of pregnancy, the purpose of prenatal evaluation is to determine and confirm adequate fetal growth, lung maturity and that the fetus continues to benefit from remaining in the uterine environment rather than timely intervention and delivery to maximize the chances of a normal postnatal development.
Assessment of fetal well-being during the third trimester includes:
Assessment of fetal movements
Fetal lung maturity determination
Assessment of placental function by means of:
o Nonstress test o Contraction stress test o Biophysical profile test o Doppler fetal umbilical arterial blood flow velocity/resistance o Ultrasonography
Nonstress test (NST) is a simple procedure by which the fetal heart rate is monitored recording simultaneously the uterine activity. A reactive nonstress test requires:
Heart rate of 120 to 160 beats per minute
Normal beat-to-beat variability
Two accelerations of more than 15 beats per minute lasting more than 20 seconds each within a 15-minute time period
A nonreactive nonstress test may reflect a prior episode of intrauterine asphyxia, a late sign of fetal asphyxia or be a nonspecific benign pattern.
Contraction stress test (CST) is used to monitor the fetal heart response to uterine contractions (spontaneous or induced with Pitocin). For a CST to be considered valid, the uterine contractions must:
Occur with a frequency of 3 in 10 minutes
Occur within 30 minutes
Last 40 to 60 seconds duration
Uterine contractions cause a diminution in the blood flow to the uterus and placenta which is well tolerated by a fetus that is not compromised. The appearance of late decelerations with uterine contractions may represent a poorly tolerated transient state of hypoxia when blood flow to the placenta is decreased. A CST is considered positive (abnormal) if late decelerations are present in 50% or more of the uterine contractions.
Biophysical profile test (BPP) is a noninvasive test that predicts the presence or absence of fetal asphyxia and the risk of fetal death in-utero. It combines the nonstress test with the assessment of:
Amniotic fluid volume
Fetal breathing movements
Fetal muscle tone
Each parameter is assigned a score from 0 to 2 points. The combination of a nonstress test and an 8 out of 8 points indicates a low risk and the need for weekly testing. The lower the score, the stronger the suggestion that immediate delivery is in the best benefit of the fetus.
Doppler fetal umbilical blood flow study measures the velocity and resistance to blood flow and assesses the placental function. Decreased flow velocity during diastole indicates placental insufficiency and in severe cases, the need for intervention. In severe cases of placental insufficiency, the diastolic flow may stop completely and even reverse itself.
Ultrasonography is the most valuable test to detect fetal anomalies as well as the estimation of fetal growth. Detection of intrauterine growth restriction (IUGR) requires additional testing to confirm fetal well-being. Growth pattern is more important than the actual estimated fetal weight at any particular point in time. Assessment of amniotic fluid volume is also meaningful in determining the status of the fetus. The appearance of diminished volume of amniotic fluid (oligohydramnios) is clinically significant.
Common mistakes in monitoring fetal well-being during the third trimester include:
Failure to order tests
Failure to schedule tests at appropriate intervals
Failure to correctly interpret tests
Failure to follow-up abnormal tests results
Failure to intervene and promptly deliver a patient in which tests reveal placental insufficiency
If your child was injured as a result of intrauterine fetal hypoxia (asphyxia or placental insufficiency) that was diagnosable, avoidable and treatable, you may have a valid cause of action. The injury may be the result of a medical provider's mistake in handling an obstetrical condition. Your child and you as parents of the child are entitled to receive compensation. If your child's condition was the result of medical negligence, allow Dr. Borten and the Boston area medical malpractice attorneys at Gorovitz & Borten help you assert your rights and get the compensation you deserve.
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