Передчасні пологи

Antibiotics effective against group B streptococci are given pending negative anovaginal cultures (2). Choices for antibiotics include the following:

• For women without penicillin allergy: Penicillin G 5 million units IV followed by 2.5 million units every 4 hours or ampicillin 2 g IV followed by 1 g every 4 hours

• For women with penicillin allergy but a low risk of anaphylaxis (eg, maculopapular rash with prior use): Cefazolin 2 g IV followed by 1 g every 8 hours

• For women with penicillin allergy and an increased risk of anaphylaxis (eg, bronchospasm, angioneurotic edema, or hypotension with prior use, particularly within 30 minutes of exposure): Clindamycin 900 mg IV every 8 hours if anovaginal cultures show susceptibility; if cultures document resistance or results are unavailable, vancomycin 20 mg/kg IV every 8 hours (maximum dose of 2 g)

Urinary tract infections and STIs are treated, if diagnosed.

If the cervix dilates, tocolytics (drugs that stop uterine contractions) can usually delay labor for at least 48 hours so that corticosteroids can be given to reduce risks to the fetus. Tocolytics include

• A calcium channel blocker

• Prostaglandin inhibitors

No tocolytic is clearly the first-line choice; choice should be individualized to minimize adverse effects.

Prostaglandin inhibitors may cause transient oligohydramnios and fetal renal damage if used for more than 48 consecutive hours. They are contraindicated after 32 weeks gestation because they may cause premature narrowing or closure of the ductus arteriosus.

IV magnesium sulfate should be considered in pregnancies < 32 weeks for the purpose of neuroprotection. In utero exposure to the drug appears to reduce the risk of severe neurologic dysfunction (eg, due to intraventricular hemorrhage), including cerebral palsy, in neonates.

If the fetus is 24 to 34 weeks, women are given corticosteroids unless delivery is imminent. Another course of corticosteroids can be considered if all of the following are present:

• The pregnancy is < 34 weeks.

• The last course was given ≥ 7 days prior (3, 4).

Corticosteroids should also be considered in the following circumstances

• At 34 0/7 weeks to 36 6/7 weeks gestation if women are at risk of delivering within 7 days and no prior corticosteroids have been given (2, 3)

• Starting at 23 0/7 weeks gestation if there is a risk of preterm delivery within 7 days (2, 3).

• At 22 0/7 weeks to 22 6/7 weeks gestation if neonatal resuscitation is planned and after appropriate parental counseling (4)

One of the following corticosteroids may be used:

• Betamethasone 12 mg IM every 24 hours for 2 doses

• Dexamethasone 6 mg IM every 12 hours for 4 doses

These corticosteroids accelerate maturation of fetal lungs and decrease risk of neonatal respiratory distress syndrome, intracranial bleeding, and mortality.

An injectable progestin is no longer recommended for women with a history of preterm delivery to reduce the risk of recurrence. Though previously recommended, supporting evidence has been refuted, and the US Food and Drug Administration (FDA) withdrew approval of 17-alpha hydroxyprogesterone caproate (17-OHPC) for this indication in April 2023 (5).

The Society for Maternal Fetal Medicine (SMFM) also discourages continued prescribing of 17-OHPC, including through compounding pharmacies (6). However, SMFM advises it is reasonable to offer either cerclage or vaginal progesterone to patients who have a history of preterm birth and who are diagnosed with a short cervix (< 25 mm) before 24 weeks gestation. SMFM encourages a shared decision-making process regarding the use of vaginal progesterone for primary prevention of recurrent preterm birth if cervical length is ≥ 25 mm, especially for patients who were treated with a progesterone formulation for preterm birth prevention in a prior pregnancy. In addition, SMFM does not recommend changing indications for cerclage or recommendations against activity restriction.

1. 1. American College of Obstetricians and Gynecologists’ Committee on Practice Bulletins—Obstetrics: Practice Bulletin No. 171: Management of Preterm Labor. Obstet Gynecol 128(4):e155-64. doi: 10.1097/AOG.0000000000001711

2. 2. American College of Obstetricians and Gynecologists (ACOG): ACOG Committee Opinion, Number 797: Prevention of group B streptococcal early-onset disease in newborns. Obstet Gynecol 135 (2):e51–e72, 2020. Reaffirmed 2022.

3. 3. American College of Obstetricians and Gynecologists (ACOG): ACOG Committee Opinion No. 713 Summary: Antenatal corticosteroid therapy for fetal maturation. Obstet Gynecol 130(2):493–494, 2017. doi: 10.1097/AOG.0000000000002231. Reaffirmed 2024.

4. 4. American College of Obstetricians and Gynecologists (ACOG): ACOG Practice Advisory: Use of Antenatal Corticosteroids at 22 Weeks of Gestation, September 2021. Reaffirmed October 2022.

5. 5. Conde-Agudelo A, Romero R: Does vaginal progesterone prevent recurrent preterm birth in women with a singleton gestation and a history of spontaneous preterm birth? Evidence from a systematic review and meta-analysis. Am J Obstet Gynecol 227(3):440-461.e2, 2022. doi:10.1016/j.ajog.2022.04.023

6. 6. Society for Maternal-Fetal Medicine (SMFM): Electronic address: pubs@smfm.org; SMFM Publications Committee. Society for Maternal-Fetal Medicine Statement: Response to the Food and Drug Administration's withdrawal of 17-alpha hydroxyprogesterone caproate. Am J Obstet Gynecol 229(1):B2-B6, 2023. doi:10.1016/j.ajog.2023.04.012