Management of Second Pregnancy After Prior Second-Trimester Abortion

Initial Management Strategy

The American College of Obstetricians and Gynecologists recommends beginning 17-alpha-hydroxyprogesterone caproate (17P) 250 mg intramuscularly weekly starting at 16-20 weeks of gestation and continuing until 36 weeks for women with a history of spontaneous preterm birth, including second-trimester abortion, with a moderate-to-high strength of evidence 1, 2, 4, 5.
The Society for Maternal-Fetal Medicine consistently recommends this approach for singleton gestations with prior spontaneous preterm birth between 20 and 36 6/7 weeks, with a moderate-to-high strength of evidence 4, 5.

The Society for Maternal-Fetal Medicine recommends performing serial transvaginal ultrasound cervical length assessments every 2-4 weeks from 16-24 weeks of gestation to allow for risk stratification and guide subsequent interventions, with a moderate strength of evidence 1, 2.
Approximately 69% of women with prior spontaneous preterm birth maintain a cervical length >25 mm throughout pregnancy, and placing cerclage in all patients would expose the majority to unnecessary procedural risks when they would not benefit from the intervention, with a moderate strength of evidence 4, 7.

If cervical length remains >25 mm, the American College of Obstetricians and Gynecologists recommends continuing 17P therapy alone and routine obstetric care, with a moderate strength of evidence 2, 6.
If cervical length shortens to ≤25 mm before 24 weeks, the Society for Maternal-Fetal Medicine recommends offering cervical cerclage placement while continuing 17P therapy, with a moderate strength of evidence 2, 6, 1.
If cervical length is ≤20 mm, the Society for Maternal-Fetal Medicine strongly considers cerclage placement, as this threshold represents significant cervical insufficiency, with a moderate strength of evidence 1, 2.

The American College of Obstetricians and Gynecologists does not recommend substituting vaginal progesterone for 17P in this patient population, as multiple randomized controlled trials have failed to demonstrate efficacy of vaginal progesterone in reducing recurrent preterm birth in women with prior spontaneous preterm birth, with a high strength of evidence 4, 5, 7.
If cervical shortening develops despite 17P therapy, the Society for Maternal-Fetal Medicine recommends continuing 17P rather than switching to vaginal progesterone, as there is no evidence that changing progestogen formulations provides additional benefit, with a moderate strength of evidence 4, 5, 7.