Chapter 42: Preterm Birth Flashcards
Define: A. SGA B. LGA C. Low birthweight D. Very low birthweight E. Extremely low birthweighr
SGA <10th percentile LGA >90th percentile LBW 1500-2500g VLBW 1000-1500g ELBW 500-1000g
Define: A. Early preterm B. Late preterm C. Early term D. Term
Early PT <33 6/7 wks
Late PT 34-36 wks
Early term 37-38 6/7 wks
Term 39-40 6/7wks
True or False.
Newborns born before 37 weeks suffer various morbidities, largely due to organ system immaturity.
True
After achieving a birtheeighht of _______ grams or a gestational age of ____ weeks for females or ____ weeks for males, survival rates reach 95%.
After achieving a birtheeighht of >= 1000 grams or a gestational age of 28 weeks for females or 30 weeks for males, survival rates reach 95%.
This term is defined as the lower limit of fetal maturation compatible with extrauterine survival.
Threshold of viability.
Active brain development occurs in what trimester?
2nd and 3rd
Enumerate morbidities of newborns born during the periviable period (20-26 weeks AOG).
Hypoxic-ischemic injury and sepsis Intellectual disability Cerebral palsy Blindness Seizure Spastic quadriparesis
True or false.
Retinopathy of prematurity is a long-term ophthalmologic problem among very low birthweight infants.
False. It is a short term problem.
Long term problems include: blindness, retinal detachment, myopia and strabismus.
True or false.
Delivery before 23 weeks typically results in death, and survival rates approximate only 10%.
False.
Delivery before 23 weeks typically results in death, and survival rates approximate only 10%.
Additional info:
For those who live, morbidity is universal.
Those born <25weeks are believed to be specially susceptible to brain injury
Enumeration.
The obstetric care consensus document addresses management ootions based on the clinical caharacteritics of a given pregnancy. Enumerate monmodifiable and potentially modifiable factors.
Nonmodifiable factors:
Fetal gender
Fetal weight
Plurality
Potentially modifiable factors: Location of delivery Intent to intervene by CS or induction Corticosteroids Magnesium sulfate
According to the Obsteteic Care Consensus, when should CS delivery be considered for fetuses at:
A. 23-24 weeks?
B. Below 20 weeks?
Consider CS at:
23-24wks for fetal indications
Below 22 weeks for maternal indications.
Additional Info:
In Parkland Hospital, CS delivery for fetal indications are practiced in women at 25 weeks and beyond.
At 24 weeks, CS delivery is not offered unless EFW is at 750g or greater.
Distribution of preterm births by gestational age.
34-36wks: 71.3%
32-33wks: 12.1%
28-31wks: 9.5%
27wks and below: 7.1%
80% of late preterm births are due to:
A. Spontaneous labor and PPROM B. Hypertension C. Abruptio placenta D. Placenta previa E. Fetal complications
A.
Soontaneous labor 45% PPROM 35% Hypertension 13% Fetal complications 2% Abruptio 1% Previa 1% Others 3%
Enumerate:
4 direct causes of preterm births.
Preterm labor with intact BOW (40-45%)
PPROM (30-35%)
Maternofetal indications (30-35%)
Twins and higher-order multifetal births
All of the following are major causes of spontaneous preterm labor, EXCEPT:
A. Maternal-fetal stress B. Multifetal gestation C. Premature cervical changes D. Infection E. Uterine distention
B. Multifetal gestations
4 Major Causes of spontaneous preterm labor: Uterine distention Maternal-fetal stress Premature cervical changes infection
All of the following are upregulated during labor and contributes to uterine distention, EXCEPT:
A. Contraction-associated proteins (CAPs)
B. Estriol
C. Stretch-induced potassium channel (TREK-1)
D. Gastrin-releasing peptides (GRPs)
C. TREK-1
- upregulated during gestation, downregulated during labor
- potential role in uterine relaxation during pregnancy
Additional Info:
CAP genes that are influenced by stretch include those that code for gap junction proteins like connexin 43, oxytocin receptors and prostaglandin synthase.
GRPs are increased with stretch and promote myometrial contractility.
During maternal stress, maternal serum levels of placental-derived CRH is elevated, raising adult and fetal adrenal steroid hormone production leading to early loss of uterine quiescence.
Enumerate.
Mechanisms by which maternal-fetal stress translate to preterm birth. (2)
Activation of placental-adrenal endocrine axis
Premature cellular senescence
Aging of fetal and decidual cells precipate release of uterotonic signals for uterine activation at term.
True or false: Cervical Dysfunction
- In most cases, premature cervical remodeling precedes premature labor onset.
- Reduction of mechanical competence of the cervix due to genetic mutations of collagen and elastic fiber components may cause cervical dysfunction.
- Group B streptococcal colonization enhance risk of preterm birth by screting hyaluronidase.
All are true.
Hyaluronidase degrades hyaluronic acid in the cervicovaginal epithelia which aids in bacterial ascension.
Bacteria can gain access to intrauterine tissues through the following, EXCEPT:
A. Transplacental transfer of infection
B. Retrograde flow of infection into the peritoneal cavity via fallopian tubes
C. Ascending infection
D. NOTA
Ffup question:
Which is the most common route?
D. NOTA
Ascending infection is the most common entey route.
This is inflammation in the absence of detectable intraamnionic microorganisms.
Sterile intraamnionic infection
True or false.
The earliier the onset of preterm labor, the lesser the likelihood of underlying infection.
False.
The earliier the onset of preterm labor, the greater the likelihood of underlying infection.
At term, the amnionic fluid is infiltrated by bacteria as a consequencr of labor, whereas in preterm, bacteria represent an inciting cause of labor.
Enumeration.
Microorganisms frequently detected in the amnionic fluid of women in preterm labor.
Gardnerella vaginalis
Fusobacterium
Mycoplasma hominis
Gardnerella urealyticum
True or false.
The diversity and richness of microbe populations are increased during pregnancy and become less stable.
False.
The diversity and richness of microbe populations are REDUCED during pregnancy and become MORE stable.
Which of the following is a risk factor for PPROM?
A. Body mass index >19.8
B. Alcohol consumption
C. Lower socioeconomic status
D. Obesity
C. Lower socioeconomic status
Associated Risk factors for PPROM: Low socioeconomic status BMI <19.8 Cigarette smoking Nutritional deficiencies
This trial showed that birth defects were associated with preterm birth and low birthweight neonates.
FASTER trial
First and Second Trimester Evaluation Risk
Deficiencybof this bitamin is associated with preterm birth.
A. Vitamin A
B. Vitamin B
C. Vitamin C
D. Vitamin D
C. Vitamin C
Intervals of less than _____ months and more than ____ months were associated with greater risk for both preterm birth and SGA newborns.
Intervals of less than 18 months and more than 59 months were associated with greater risk for both preterm birth and SGA newborns.
Which of the following is the most important riak factor for preterm labor?
A. Infection B. Maternal age C. Multifetal gestation D. Short stature E. Prior preterm birth
E. Prior preterm birth
Additional info:
Recurrent preterm delivery risk for prior preterm birth is threefold.
Recurrent births occur with 2 weeks of AOG of prior preterm delivery.
Causes of prior preterm delivery also recur.
Prior indicated preterm birth is strongly associated with subsequent spontaneous preterm birth.
Enumeration.
Factors that influence risk of recurrent preterm birth. (3)
Frequency of prior preterm deliveries
Severity as measured by AOG
Order by which preterm delivery occurred
Bacterial Vaginosis
________ is to relative concentrations of bacterial morphotypes as ________ is to clinical assessment.
Nugent score
Amsel criteria
Which of the following are associated with development of bacterial vaginosis? May have more than one answer.
Chronic stress
Frequent douching
Ethnicity
TNF-a genotype
All are associated.
True of fetal fibronectin:
A. Values exceeding 30ng/mL are considered positive.
B. It is present in high concentrations in amnionic fluid and in fetal blood.
C. It functions in intercellular adhesion during implantation and in maintenance of placental adherence to uterine decidua
D. It may be used solely for screening preterm labor.
C.
Fetal fibronectin
Values exceeding 50ng/mL are considered positive.
It is present in high concentrations in amnionic fluid and in MATERNAL blood.
It functions in intercellular adhesion during implantation and in maintenance of placental adherence to uterine decidua
It is used in conjunction with cervical length measurement.
Why is transvaginal UTZ better than transabdominal when assessing cervical length?
It is not affected by:
Maternal obesity
Cervical position
Shadowing from the fetal presenting part
