PRETERM LABOR Flashcards
Sub-categories of preterm birth, based on gestational age
- Extremely preterm : less than 28 weeks
- Very Preterm : 28-32 weeks
- Moderate to late preterm : 32-36 6/7 weeks
Refers to <37 weeks AOG but more than 20 completed weeks
Preterm
37-41 weeks AOG
Term
Sub-categories of term birth, based on gestational age:
- Early term (37-38 6/7 weeks)
- Full term (39-40 6/7 weeks)
- Late term (41-41 6/7 weeks)
- Post term (42 & onwards)
Defined as regular contractions resulting to cervical effacement & dilation that occurs before 37 completed weeks but after 20 completed weeks.
Preterm Labor
Risk Factors / Causes
- History of Premature birth
- Smoking & Drug Use
- Short interpregnancy interval
- Previous surgeries involving the cervix
- Congenital abnormalities of the uterus
- Cervical insuffiency
- Infections
- Maternal stress
- Dehydration
- Uterine distention
- Maternal factors
- Placental issues
Strongest risk factor for preterm labor
History of Premature birth
Why is smoking & drug use a risk factor
Vasoconstriction 🡪 decrease uterine / placental perfusion 🡪placental insufficiency
How does infections become a risk factor or a cause for preterm labor
Microbial invasion 🡪 causes inflammation on uterine muscles/weakening of amniotic sac 🡪 triggers release of prostaglandins 🡪 uterine contractions
2 reasons how dehydration is a risk factor / cause?
- Can lead to oligohydramnios 🡪 uterine irritation / fetal stress 🡪 contractions
- Can stimulate release of ADH to retain water 🡪 ADH has similar chemical structure as oxytocin 🡪 mistaken as oxytocin 🡪uterine contractions
How is maternal stress a risk factor / cause
oxytocin levels are high under stressful conditions 🡪 uterine contractions
How uterine distention can lead to premature labor
Excessive uterine stretch can send signals that the uterus is of adequate size & that fetus is already “term” 🡪uterine contractions
Predictors of Preterm Labor
1) Measurement of cervical length via UTZ
2) Fetal Fibronectin test
Cervical length that is a good predictor that woman can go into preterm labor
< 2-2.5 cm
Used to rule out preterm labor -In normal conditions, fFn is found at very low levels in cervico-vaginal secretions
Fetal Fibronectin test
Is a protein that is believed to help keep the amniotic sac “glued” to the lining of the uterus.
Fetal fibronectin
Elevated levels of fibronectin indicates preterm labor by how much.
> or equal to 50 ng/mL
