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20 Cards in this Set
- Front
- Back
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Preterm birth: - Definition? |
Between 20-37 weeks. |
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Preterm birth: - Prevalence by ethnicity? |
Twice as high in blacks than in whites. |
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Common causes of preterm birth? |
1. Spontaneous: 35-37%
2. Multiple pregnancies: 12-15%
3. Premature premature rupture of membranes (PPROM): 12-15%
4. Pregnancy-associated HTN: 12-14%
5. Cervical incompetence or uterine anomalies: 12-14%
6. Antepartum hemorrhage: 5-6%
7. Intrauterine growth restriction (IUGR): 4-6% |
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Four potential pathways leading to preterm delivery? |
1. Infection (cervical)... BV is one 2. Placental-vascular 3. Psychosocial stress and work strain (fatigue) 4. Uterine stretch (multiple gestations) |
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What test can you do to predict preterm birth? (that tests the infection pathway) |
Cervical and vaginal fetal fibronectin.
This substance is a basement membrane protein produced by the fetal membranes. When the fetal membranes are disrupted, as with repetitive uterine activity, shortening of the cervix, and in the presence of infection, fibronectin is secreted not the vagina and can be tested.
A positive fetal fibronectin test at 22 to 24 weeks predicts more than half of the spontaneous preterm births that occur before 28 weeks. A positive test for fetal fibronectin is significantly associated with a short cervix, vaginal infections, and uterine activity. A negative test is the best predictor of a low risk for preterm delivery. |
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Placental-Vascular Pathway: - Begins when? - What immunologic changes occur? - What other changes? |
- Begins at time of implantation, when there are changes at the placental-decidual-myometrial interface.
- Immunologic changes: TH1 changes to TH2 antibody profile, in which blocking antibody production is thought to prevent rejection.
- Also, trophoblasts are invading the spiral arteries of the decade and myometrium, thus assuring that a low-resistance vascular connection is established. |
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How does stress-strain pathway play a role in preterm delivery? |
Stress response --> release of cortisol and catecholamines.
Cortisol --> initiates early placental corticotrophin-releasing hormone (CRH) gene expression, and elevated CRH initiates labor at term.
Catecholamines --> affected blood flow to uteroplacental unit and cause uterine contractions (norepinephrine). |
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How does uterine stretch increase preterm labor and what are some examples that lead to uterine stretch? |
Uterine stretch leads to physiological mechanism that facilitates the process of emptying the uterus.
Polyhydraminos and multiple gestations are examples. |
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Preterm labor diagnosis criteria? |
Between 20-37 weeks and:
1. Documented uterine contractions (four per 20 minutes) AND 2. Documented cervical changes (effacement of 80% or cervical dilation of 2 cm or more) |
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What do you do for someone who is in preterm labor? |
1. FIRST make sure they are hydrated and give bed rest. 20% resolve.
2. Cultures should be obtained for group B strep
3. Initiate antibiotics. Give 7-day course of ampicillin, erythromycin, or both. If allergic to PNC, give clindamycin.
4. CBC, blood glucose, serum electrolytes, urinalysis, and urine culture and sensitivity. Do U/S of fetus.
5. If the patient does not respond to ed rest and hydration, tocolytic therapy is instituted! |
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Examples of uterine tocolytic agents? |
1. Magnesium sulfate
2. Nifedipine
3. Prostaglandin Synthetase Inhibitors - Short term use only. |
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Magnesium sulfate: - How does it work? - Dose for preterm labor? - Duration of treatment? - Side effects? |
- Works by competing with calcium for entry into the cell at the time of depolarization. Successful competition results in an effective decrease of intracellular calcium ions, resulting in myocetrial relaxation.
- Higher levels needed than for preeclampsia. 5.5-7.0 mg/dL. After loading dose is given (6 grams over 15-20 mins), a continuous IV infusion is maintained, and plasma levels should be determined until therapeutic levels are reached.
- Once successful tocolysis has been achieved, the infusion is continued for at least 12 hours, and then the infusion rate is weaned over 2 to 4 hours and then discontinued. For high-risk patients (advanced cervical dilation or continued labor in very-low-birth-weight cases), the infusion can be continued until the fetus has been exposed to glucocorticoids to enhance lung maturity.
- Common SE is feeling of warmth and flushing on first administration. Respiratory depression is seen at levels of 12 to 15 mg/dL, and cardiac conduction defects and arrest is seen at higher levels.
- In the fetus, a low plasma calcium level may also be demonstrated. |
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Nifedipine: - Give how? - How does it work? - SE? |
- Give orally
- Works by inhibiting the slow, inward current of calcium ions during the second phase of the action potential of uterine smooth muscle cells and may gradually replace IV magnesium sulfate.
- SE are HA, cutaneous flushing, hypotension, and tachycardia. The later two can be avoided by hydrating and using support stockings |
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Indomethacin: - Drug class? - Administered how? - Used for what? - SE? - What to do if given? |
- Prostaglandin Synthetase Inhibitor
- Given orally or rectally, SHORT TERM ONLY!
- Used to stop labor.
- SE: Oligohydraminos and premature closure of the fetal ductus arterioles, which may lead to pulmonary HTN and cardiac failure. In addition, indomethcin decreases fetal renal function and exposes infants to a greater risk of necrotizing enterocolitis, intracranial hemorrhage, and patent ductus arterioles.
- ST use may be acceptable, but do an U/S after to check for ductus arterioles flow. |
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Antibiotic therapy controversy? (in preterm labor) |
The use of prophylactic AB in women in preterm labor may prevent the progression of a subclinical infection to clinical amnionitis. |
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Contraindications to Tocolytic Therapy? |
1. Severe preeclampsia 2. Severe bleeding f/ placenta previa or abruptio placentae 3. Chorioamnionitis 4. Intrauterine growth restriction 5. Fetal anomalies incompatible with life 6. Fetal demise |
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Antenatal corticosteroids (glucocorticoids): - Benefits? - Gestational age? - Treatment dose and duration? |
- Reduces incidence of RDS and intraventricular hemorrhage
- Between 24-34 weeks
- Give 2 doses of 12 mg betamethasone, IM 24 hours apart, OR... - Give 4 doses of 6 mg dexamethasone, IM 12 hours apart.
- Optimal benefits begin 24 hours after initiation of therapy and lasts 7 days. |
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What is the lower limit of potential viability of a neonate in terms of WEEKS and GRAMS? |
24 weeks or 500 grams |
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What might acidosis do to the fetus? |
Acidosis at birth adversely affects respiratory function by destroying surfactant and delaying its release. |
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When is vaginal delivery preferred? When is C section preferred in preterm? |
- With a vertex presentation, vaginal delivery is preferred, provided that fetal acidosis and delivery trauma are avoided. Use of outlet forecast and an episiotomy to shorten the second stage are advocated.
- For the breech fetus estimated at < 1500 g, neonatal outcome is improved by cesarean birth. |
