Preterm Birth

Question 1

Define low birthweight vs preterm birth

Answer 1

Low birthweight is for babies who were born too small

Preterm birth is for babies who were born TOO EARLY

Question 2

Define the different ranges of low birthweight babies (3)

Answer 2

Normal = 3000
Low birthweight = 1500g - 2500g
Very low birthweight = 500 - 1500
Extremely low birthweight = 500 - 1000

Question 3

Define the different ranges of preterm and term births

Answer 3

Early preterm - before the 34th week
Late preterm - 34-36 weeks
Early term - 37-39 weeks
Late term - 40 - 42 weeks

additional note:
preterm = before 37 weeks
term = 37-42
post-term = >42 weeks

Question 4

What are the three main causes of preterm birth?

How do you differentiate two of the answers?

Answer 4

1. Spontaneous preterm labor
2. Preterm premature rupture of membranes
3. Multifetal pregnancy

Spontaneous labor with intact membranes must be differentiated from preterm premature rupture of membranes AS THE CAUSE of preterm birth

Question 5

What are the FOUR MAJOR CAUSES of spontaneous preterm labor?

Answer 5

1. Uterine distention (multifetal pregnancies, polyhydramnios, )
2. Maternal-fetal stress
3. Premature cervical changes
4. Infection

Question 6

For Uterine Distention, what are two well-recognized risks?

Answer 6

Multiple pregnancies (kaya nga overdistended)

Hydramnios

Question 7

How does uterine distention lead to preterm labor?

hint: it leads to a loss of ______ due to the release of (3)

Answer 7

Leads to a loss of quiescence

Due to the release of:

1. contraction associated protein
2. gastrin releasing peptides
3. stretch induced potassium channel - TREK-1

Question 8

Maternal fetal stress leading to spontaneous labor is caused by the elevation of what hormone due to stress?

Answer 8

cortisol

Stress leads to increase in CRH -> works with ACTH to induce maternal and fetal steroid production -> increase in fetal DHEAS -> which leads to an increase in estriol.

cortisol and estriol both lower uterine quiescence

Question 9

How does infection cause preterm labor?

Expound on how these three come from infection and lead to preterm labor:

1. Inflammation
2. Prostaglandins
3. Premature activation of the fetal HPA

Answer 9

When the mother gets infected during pregnancy, the bacteria releases endotoxins
The endotoxins reach the leukocytes which produce cytokines and chemokines
Cytokines and chemokines will then promote cascades leading to:

1. inflammation -> PROTEASE synthesis -> cervical ripening + Preterm prematuer rupture of membranes -> preterm labor
2. Prostaglandins -> cervical ripening + myometrial activation -> preterm labor
3. activation of fetal HPA -> release of CRH -> ACTH -> fetal DHEAs -> estriol -> myometrial activation -> preterm labor

alternatively -> CRH -> ACTH -> cortisol -> prostaglandins -> myometrial activation + cervical ripening

Question 10

Give the THREE sources of intrauterine infection

what is the most common route?

Answer 10

1. transplacental
2. retrograde flow
3. Ascending infection of bacteria -> MOST COMMON ROUTE

Question 11

Give the FOUR microbes associated with preterm birth

Answer 11

1. Gardnerella vaginalis
2. Fusobacterium species
3. Mycoplasma hominis
4. Ureaplasma urealyticum

Question 12

Give the FOUR categories of bacterial infection in pregnant women

Answer 12

1. Category I - Bacterial vaginosis
2. Category II - Decidual infection
3. Category III - Amniotic infection
4. Category IV - Fetal systemic infection

Question 13

Give the definition of preterm premature rupture of membranes

Answer 13

Rupture of the membranes BEFORE 37 weeks are completed AND before the onset of labor

(difference from simple PROM is that here it is below 37 weeks, not just before the onset of labor)

Question 14

What are major predisposing events to PPROM

Answer 14

1. Intrauterine infections
2. Oxidative stress
3. Early cell senescence

Question 15

Give 10 lifestyle factors that contribute to preterm labor (9)

Answer 15

1. Cigarette smokinh
2. Inadequate maternal weight gain
3. Illicit drug use
4. Extremes of weight
5. Extremes of age
6. poverty
7. Short stature
8. VITAMIN C DEFICIENCY
9. Psychological factors such as anxiety, depression, stress

Question 16

Give the factors which contribute to preterm birth (7)

which is the most important risk factor?

Answer 16

1. Pregnancy Factors
2. Lifestyle factors
3. Genetic factors
4. Periodontal disease - gum inflammation is a chronic anaerobic inflammation
5. Interval between birth - Intervals below 18 months and greater than 59 months
6. Prior preterm birth - MOST IMPORTANT
7. Infection

Question 17

Does antibiotic prophylaxis decrease preterm birth rate?

Answer 17

NO.

NOT RECOMMENDED in women with preterm labor with unruptured membranes

Question 18

Define bacterial vaginosis

Answer 18

When the normal flora of the vagina (lactobacillus-predominant flora) is replaced with Gardnerella vaginalis, Mycoplasma hominis, Mobiluncus

Question 19

How do you assess Bacterial Vaginosis?

Elaborate on that CRITERIA

Answer 19

Use the Amsel’s criteria 3 our of the 4 criteria must be met

1. Homogenous, non-clumping vaginal discharge
2. Fishy odor when potassium hydroxide is added
3. presence of CLUE CELLS on microscopy
4. pH greater than 4.5

Question 20

What are the FOUR types of infections related to preterm labor?

Answer 20

1. Bacterial Vaginosis
2. Periodontitis
3. Trichomoniasis
4. Lower Genital Tract infections

Question 21

What is the treatment of choice for bacterial vaginosis?

Answer 21

Metronidazole 500mg BID (twice a day) for 7 days

Question 22

What is the predominant infection in periodontitis?

Treatment of choice?

Answer 22

Fusobacterium

Teeth cleaning plus metronidazole

Question 23

What is the offending agent in Trichomoniasis?

Diagnosis?

Treatment of choice?

Answer 23

Trichomonas vaginalis

wet mount of vaginal secretions OR culture in a diamond medium

Metronidazole 500mg BID for 7 days

Question 24

What is the main offending organism in lower genital tract infections?

Diagnosis?

Drug(s) of choice?

Answer 24

Chlamydia trachomatis

ligase chain reaction assay

Doxycycline AND Azithromycin (1g then 500mg every day for 2 days)

Question 25

Give the factors which would help you diagnose Preterm labor (5) Expound on each one :) are they all recommended? or useful?

Answer 25

1. Symptoms - regular contractions before 37 weeks associated with cervical change - cramps, lower back pain, watery vaginal discharge 2. Cervical change - Asymptomatic cervical dilation after mid-pregnancy could be normal or could entail preterm labor 3. Ambulatory uterine monitoring - NOT RECOMMENDED, too expensive and does not help reduce preterm birth rates 4. Fetal fibronectin - produced by the fetal amnion cells - detected in cervico-vaginal discharge in normal pregnancies with intact membranes at term. It could be a sign of preterm labor if detected before term with intact membranes 5. Cervical length measurement - Progressively shorter cervical canals are associated with preterm birth - Mean cervical length at 24 weeks is 35mm, if shorter, may risk preterm labor - WOMEN WITH PREVIOUS PRETERM BIRTH must undergo cervical ultrasonography between 16-24 weeks AOG. In summary: Universal screening of sonographically measured cervical length and quantitative measurement of vaginal fFN levels were evaluated as predictors of women who would spontaneously deliver before 37 weeks.

Question 26

Are prenatal cervical examinations helpful? or harmful?

Answer 26

Neither

Question 27

When should you consider cervical cerclage to prevent preterm birth?

Answer 27

1. Singleton pregnancy 2. Prior spontaneous birth before 34 weeks 3. Cervical length <25mm 4. Gestational age <24 weeks

Question 28

How do you diagnose PPROM?

Answer 28

1. Fluid leakage 2. pH of 7.1-7.2 3. Ultrasound confirmation 4. sterile speculum examination

Question 28

How do you diagnose PPROM?

Answer 28

1. Fluid leakage 2. pH of 7.1-7.2 3. Ultrasound confirmation

Question 29

Give the management for PPROM depending on the AOG for 24-31 weeks PPROM, should tocolytics be administered?

Answer 29

1. 34 weeks or more = you can plan for delivery and induce labor. Give Group B strep prophylaxis as well. OR you can give corticosteroid therapy up until 37 weeks 2. 32-33 weeks = Expectant management ( you wanna at least make it reach 34 weeks). You may start giving Group B strep prophylaxis as well as antimicrobials to prolong latency and corticosteroid therapy 3. 24-31 weeks = Same as 32-33 weeks except add magnesium sulfate for neuroprotection. There is no consensus on use of tocolytics 4. Before 24 weeks = Group B strep prophylaxis is NOT RECOMMENDED. Though you should give corticosteroid therapy with expectant management.

Question 30

Give the management for preterm labor and expound a bit

Answer 30

1. Amniocentesis = detect infection, NOT ROUTINELY RECOMMENDED 2. Corticosteroids for fetal lung maturity = 12mg betamethasone every 24 hours for 2 doses OR dexamethasone 6mg every 12 hours for 4 doses 3. Magnesium sulfate = for neuroprotection, prevention of cerebral palsy. 6grams bolus for 2-30mins followed by 2grams per hour for 12 hours 4. Antimicrobials = not recommended if soley used to prevent labor 5. Emergency rescue cerclage 6. Tocolysis = may only delay up to 48 hours. usually used to allow for corticosteroid administtration

Question 31

Give 6 tocolytic agents with examples

Answer 31

1. Beta adrenergic receptor antagonists - ritodrine, terbutaline 2. Magnesium sulfate - may inhibit labor because it is a calcium antagonist (POTENTIALLY HARMFUL) 3. Prostaglandin inhibitors - indomethacin 4. Calcium channel blockers - Nifedipine (POTENTIALLY DANGEROUS IF PAIRED IWTH MAGSUL) 5. Atosiban - oxytocin analogue, acts as an oxytocin antagonist 6. Nitric oxide donors - Nitroglycerin - NOT EFFECTIVE