OB Guideline 22: Prolonged Pregnancy
Many descriptive labels are applied to pregnancies that go beyond the expected date of delivery (EDD). CRICO Guidelines supports ACOG’s classifications.1
Late-term: 410/7 weeks of gestation through 416/7 weeks of gestation.
Post-term: 420/7 weeks of gestation and beyond.
Risks of Prolonged Pregnancy
Fetal/Neonatal: Increased perinatal morbidity and mortality, including seizures, meconium aspiration, macrosomia, oligohydramnios, post maturity syndrome, low 5-minute Apgar scores, intrauterine fetal demise, neonatal intensive care unit admission and neonatal mortality.3
Birthing Person: Increased risk for meconium-stained fluid, shoulder dystocia, severe perineal laceration, infection, postpartum hemorrhage, assisted operative delivery and cesarean delivery.3
Accurate assessment of gestational age is of paramount importance for management of pregnancy, interpretation of test results, and timing of interventions.
(See Guideline 7.)
Risks of Induction vs. Expectant Management
Clinicians should be familiar with the acceptable alternative methods of management of late-term and post-term pregnancies. Whichever method is chosen (membrane sweep, cervical ripening agent, cervical dilator, oxytocin or amniotomy), the prenatal record must indicate that a discussion regarding management of pregnancy exceeding 41 weeks gestation occurred between the obstetrical provider and the patient and risks and benefits were reviewed. Of note, membrane sweeping after 39 weeks gestation is associated with a decreased risk of late-term and post term pregnancies.3,4
Induction risks include failed induction, complications related to the use of oxytocin or prostaglandin administration, such as uterine tachysystole (hyperstimulation) and fetal intolerance of contractions.2
Expectant management risks include but are not limited to: intrauterine fetal demise, perinatal death, meconium aspiration syndrome and dysmaturity syndrome.3
Management of Late-Term Pregnancy
The following approach to managing pregnancies that go beyond the completion of the 41st gestational week is recommended. If the nullipara or multipara patient’s cervix is:
- favorable for oxytocin induction, then oxytocin induction or amniotomy is preferred; fetal surveillance is an acceptable alternative;
- not favorable for oxytocin induction, then cervical ripening followed by oxytocin induction or fetal surveillance are acceptable alternatives;
If fetal surveillance is chosen, then initiate twice-weekly fetal testing at 41 0/7. This should include an initial ultrasonographic assessment of amniotic fluid volume to detect oligohydramnios.
Management of Post-Term Pregnancy
Steps should be initiated to obtain consent and proceed to deliver the patient as soon as is feasible.
- Definition of term pregnancy. ACOG Committee Opinion No. 579. November 2013, Reaffirmed 2017. American College of Obstetricians and Gynecologists.
- Induction of labor. ACOG Practice Bulletin No. 107. August 2009, Reaffirmed 2020. American College of Obstetricians and Gynecologists.
- Management of late-term and post-term pregnancies. ACOG Practice Bulletin No. 146. August 2014, Reaffirmed 2020. American College of Obstetricians and Gynecologists.
- Boulvain, M., Stan, C.M., Iron, O. 2005. Membrane sweeping for induction of labour. Cochrane Database of Systematic Reviews, Metaanalysis, 1, CD000451. DOI: 10.1002/14651858.CD00451.pub2
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