As an intern house officer, I prepared this presentation to increase awareness about a common clinical entity that makes a big part of an obstetrician's daily work burden. I presented it to my fellow interns during our rotation in the Department of Obstetrics and Gynecology at Latifa Hospital, Dubai, UAE.
Preterm birth (PTB) is defined as a birth (ie, live born or stillborn ≥20+0 weeks of gestation) that occurs at <37+0 weeks of gestation. I am delighted to share this lively PowerPoint Presentation about preterm birth to walk you through the classification, variety of risk factors, easily made pathophysiology, diagnosis, and treatment of preterm birth. I hope you enjoy it!
PS: Use the slideshow mode in Microsoft PowerPoint for the best experience.
3. Definition
Preterm birth (PTB) is defined as a birth (ie, live born
or stillborn ≥20+0 weeks of gestation) that occurs at
<37+0 weeks of gestation
Preterm Labor 3
5. Preterm Labor 5
Gestational
Age Criteria
Criteria
WHO (World
Health
Organization)
ACOG (American
(American College
College of
Obstetrics and
Gynecology)
CDC (Centers for
for Disease Control
Control and
Prevention)
6. WHO
Preterm Labor 6
Preterm <37 weeks
Moderate to late preterm 32 to 37 weeks
Very preterm 28 to 32 weeks
Extremely preterm <28 weeks
7. ACOG and CDC
Preterm Labor 7
Preterm <37+0 weeks
Late preterm 34+0 to 36+6 weeks
Early preterm <34+0 weeks
12. Preterm Labor 12
Prior OB/GYN History
History
Maternal
Demographics and
Genetic Factors
Nutritional
Status/Physical
Activity
Current
Maternal/Pregnancy
Characteristics
13. Preterm Labor 13
Prior OB/GYN History
•Prior PTB (especially multiple PTBs or PTB at an early
early gestational age) – major risk factor
•Prior cervical surgery (eg, cone biopsy, LEEP)
•Multiple D&Es
•Uterine anomalies
14. Preterm Labor 14
Maternal Demographics and Genetic Factors
• <17 or >35 years of age
• Non-Hispanic Black race, Indigenous women
• Lower educational level (eg, <12 grades)
• Single marital status
• Lower socioeconomic status
• Short interpregnancy interval (eg, <18 months)
• Other social factors (eg, poor access to medical care, physical abuse, acculturation)
• Some genetic variants
• Personal history of preterm birth in the mother
• Family history of preterm birth in the maternal lineage
15. Preterm Labor 15
Nutritional Status/Physical Factors
• Low and high prepregnancy weight and gestational weight gain
gain
• Poor nutritional status
• Short stature
• Long working hours (eg, >80 hours/week)
• Hard physical labor (eg, shift work, standing >8 hours)
16. Preterm Labor 16
Current Maternal/Pregnancy Characteristics
• Conception by assisted reproductive technology (eg, IVF)
IVF)
• Multiple gestation
• Fetal disorder (eg, chromosome anomaly, structural
abnormality, growth restriction, death,etc)
• Early pregnancy bleeding
• Obstetric risk factors including placenta previa, placenta
placenta accreta spectrum, vasa previa, prior fundal
hysterotomy, PPROM, oligohydramnios or polyhydramnios,
polyhydramnios, preeclampsia with severe features,
gestational diabetes with poorly controlled glucose levels,
levels, and intra hepatic cholestasis of pregnancy
• Chronic maternal medical conditions
• Maternal abdominal surgery during pregnancy
Current Maternal/Pregnancy Characteristics
(CONT)
• Infection:
• Intrauterine infection, Bacterial vaginosis, trichomoniasis
trichomoniasis
• Chlamydia, gonorrhea, syphilis
• Urinary tract (eg, asymptomatic bacteriuria,
pyelonephritis)
• Severe viral infection, malaria
• Short cervical length between 14 and 28 weeks
• Positive fFN between 22 and 34 weeks
• Uterine contractions
• Psychological issues
• Substance use:
• Smoking (eg, tobacco)
• Heavy alcohol consumption
• Cocaine, heroin
21. History
• Review the patients’ detailed history with a focus on the past and
present obstetric and medical history, including risk factors for preterm
birth
• The following prodromal signs and symptoms might be present before
true labor ensues:
• Menstrual-like cramping
• Mild, irregular contractions
• Pressure sensation in the vagina or pelvis
• Vaginal discharge of mucus (ie, mucus plug, bloody show)
• Spotting, light bleeding
• Assess contraction frequency, duration, and intensity
21
22. Physical Examination
• Evaluate for the signs of preterm labor
• Examine the uterus to assess firmness, tenderness,
fetal size, fetal position, and contractions
• Review the fetal heart rate tracing
22
23. Speculum Examination
23
A speculum examination is performed using a sterile, wet non-lubricated
speculum
Estimate cervical dilation: dilation ≥3 cm supports the diagnosis of
preterm labor
Assess the presence and amount of uterine bleeding: bleeding from
placental abruption or placenta previa can trigger preterm labor
Assess fetal membrane status (intact or ruptured) by standard
methods
Use a swab to obtain a cervicovaginal fluid specimen in case fetal
fibronectin (fFN) testing is subsequently desired
24. Digital Cervical Examination
• Cervical dilation and effacement are assessed after placenta
previa and rupture of membranes have been excluded by
history and physical, laboratory, and ultrasound examinations,
as appropriate.
• It is important to distinguish between patients whose
membranes have hour-glassed (prolapsed) through a mildly
dilated and effaced cervix (which is suggestive of cervical
insufficiency) and those who are in active labor with
advanced cervical dilation and effacement.
Preterm Labor 24
26. Transvaginal Ultrasound Examination
Preterm Labor 26
• Measurement of cervical length is useful for supporting or
excluding the diagnosis of preterm labor when the diagnosis is
unclear:
• A short cervix (<30 mm) before 34 weeks of gestation is
predictive of an increased risk for preterm birth in all
populations
• A long cervix (≥30 mm) has a high negative predictive value
for preterm birth
27. Obstetric Ultrasound Examination
Preterm Labor 27
• Obstetric ultrasound examination provides useful
information besides cervical length, including
• Presence/absence of fetal, placental, and maternal
anatomic abnormalities
• Confirmation of fetal presentation
• Assessment of amniotic fluid volume
• Estimated fetal weight
29. Laboratory Evaluation
• Rectovaginal group B streptococcal culture, if not done within the
previous five weeks; antibiotic prophylaxis depends on the results
• Urine culture since asymptomatic bacteriuria and pyelonephritis is
associated with an increased risk of preterm labor and birth
• fFN in pregnancies <34 weeks of gestation with intact membranes,
cervical dilation <3cm, and cervical length 20 to 30 mm on TVUS
• Testing for sexually transmitted infections depending on the patient's
risk factors and whether antepartum testing for the infections was
recently performed
29
30. Fetal Fibronectin
for Selected
Patients
• fFN is an extracellular
matrix protein present at
the decidual-chorionic
interface.
• Disruption of this interface
releases fFN into
cervicovaginal secretions,
which is the basis for its
use as a marker for
predicting spontaneous
preterm.
• Measurement of fFN is
performed to distinguish
true preterm labor from
false labor.
32. Diagnostic Criteria
Preterm Labor 32
• The presence of regular painful uterine contractions accompanied by
cervical change (dilation and/or effacement) is sufficient to make the
diagnosis.
• The following criteria had been proposed: Uterine contractions (≥6
in 60 minutes) PLUS
• Cervical dilation ≥3 cm OR
• Cervical length <20 mm on transvaginal ultrasound OR
• Cervical length 20 to <30 mm on transvaginal ultrasound and positive fetal
fibronectin
34. Preterm
Uterine
Contractions
GA <34 weeks
Cervix dilated
≥3 cm
Preterm labor
likely
Cervix dilated
<3 cm
fFN and TVUS
Cervical length
<20 mm
Preterm labor
likely
Cervical length
20–30 mm
fFN positive
Preterm labor
likely
fFN negative
Preterm labor
unlikely
Cervical length
>30 mm
Preterm labor
unlikely
GA ≥34 weeks
No treatment for
preterm labor
Preterm Labor 34
35. Initial Management of Preterm Labor
Preterm Labor 35
• Antenatal corticosteroids: a course of betamethasone or
dexamethasone to reduce neonatal morbidity and mortality
associated with preterm birth.
• A single rescue course of antenatal steroids is indicated for pregnancies
<34+0 weeks of gestation that are at high risk of preterm delivery within the
next seven days and in which the prior course of ACS was administered more
than 14 days previously
36. Initial Management of Preterm Labor (CONT)
Preterm Labor 36
Tocolytics: tocolysis for up to 48 hours to delay birth so that the ACS can achieve its
achieve its maximum fetal effect
GBS prophylaxis: antibiotics are given to patients with known positive GBS culture
culture within the previous five weeks or if the GBS status was unknown on admission
admission until the cultures are reported
Neuroprotection: magnesium sulfate for pregnancies <32 weeks of gestation to
to provide neuroprotection against cerebral palsy and other types of severe motor
motor dysfunction in the preterm newborn
38. Question
• A 29-year-old, G2P1+1 with a twin gestation at 25 weeks presents to OB
triage complaining of irregular uterine contractions and back pain. She also reports an
increase in the amount of her vaginal discharge, but denies any "gush of fluid." She
reports that in the morning she had some very light vaginal bleeding, but it has since
resolved. She says that the babies have been active and moving as much as usual. She
thinks that she may have overdone it with too much lifting as she has been rearranging
the nursery to get it ready for the babies. She has no GI or urinary symptoms. She has had
adequate PNC and denies any problems or complications with the pregnancy. On arrival to
triage, she is placed on an external fetal monitor, which indicates uterine contractions
every 2 to 4 min. She is afebrile and her vital signs are all normal. Her gravid uterus
is nontender. The nurses call you to evaluate the patient. You decide to implement all of
the following assessments EXCEPT which one?
A. Sterile digital exam
B. Intravenous hydration
C. Bedside ultrasound
D. Urinalysis and urine culture
E. Rectovaginal swab for Group B Strep
Preterm Labor 38
39. Reference
s
• Lockwood CJ. Preterm labor: Clinical findings,
diagnostic evaluation, and initial treatment. In; Barss
VA (ed.). UpToDate; 2023. Available from:
https://www.uptodate.com/contents/preterm-labor-
clinical-findings-diagnostic-evaluation-and-initial-
treatment. Accessed on 30 May 2023.
• Robinson JN. Norwitz ER. Spontaneous preterm birth:
Overview of risk factors and prognosis. In: Barss VA.
(ed.). UpToDate; 2023.
https://www.uptodate.com/contents/spontaneous-
preterm-birth-overview-of-risk-factors-and-prognosis.
Accessed 30 May 2023. Accessed on 30 May 2023.
• Casanova R, Chuang A, Goepfert AR, Hueppchen NA,
Weiss PM. Preterm Labor. In: Beckmann and Ling’s
Obstetrics and Gynecology. 8th edn. Philadelphia:
Wolters Kluwer. 2019, p. 366.