What's new in maternal-fetal medicine: September 30, 2026

At a glance

Area	Evidence	Clinical relevance
Respiratory-virus vaccination	CDC issued 2026–27 COVID-19 vaccine guidance on September 23 and updated its 2026–27 influenza-season information on September 29. Pregnancy remains a high-risk condition for severe respiratory viral illness.	USE NOW
Amniotic fluid embolism biology	An AJOG research letter found striking inflammatory cytokine elevations in maternal blood obtained before clinical collapse in a patient who later developed fatal amniotic fluid embolism.	WATCHING
Unscheduled cesarean delivery	A JAMA analysis of 1.66 million births found substantial adoption of adjunctive azithromycin after 2016 trial evidence and a 2.0-percentage-point decline in postpartum infection for cesarean births relative to vaginal births.	REVIEW WORKFLOW
Red-cell alloimmunization	SMFM's 2026 statement on cfDNA fetal red-cell antigen genotyping clarifies where noninvasive fetal antigen testing can and cannot replace established diagnostic and surveillance pathways.	REVIEW WORKFLOW
Ultrasound infection prevention	Updated SMFM statement expands infection-control guidance beyond transvaginal ultrasound.	USE NOW
Amniotic fluid embolism	Updated SMFM initial-management checklist aligns terminology with current advanced cardiac life support guidance.	USE NOW
Prenatal congenital heart defect detection	SMFM updated quality metrics using newer fetal cardiac ICD-10-CM codes.	REVIEW WORKFLOW
Sickle cell disease	New SMFM checklists cover prepregnancy, antepartum, delivery, postpartum, and vaso-occlusive crisis care.	REVIEW WORKFLOW
High-risk pregnancy where abortion care is restricted	SMFM statement addresses counseling, referral and transfer systems, institutional collaboration, and training. SMFM source	NEW GUIDANCE
Fetal growth restriction	September AJOG review compares six contemporary international and national FGR guidelines.	WATCHING
sFlt-1/PlGF	In a retrospective cohort with ratios greater than 600, the absolute ratio added little outcome discrimination beyond gestational age and estimated fetal weight.	WATCHING
Early-onset preeclampsia	A September AJOG cohort found increasing antihypertensive-treatment escalation during expectant management was associated with increasing maternal adverse-outcome risk.	WATCHING

Society guidance and implementation

Practice updates

These items were not covered in the prior Clinical Evidence Update and either warrant workflow review now or provide important new implementation evidence.

JAMA Original Investigation · Cesarean infection prevention

Real-world data support adjunctive azithromycin for unscheduled cesarean delivery

REVIEW WORKFLOW

What the study found

Investigators used Epic Cosmos data from 1,663,441 singleton live births from 2013 through 2024. After publication of the 2016 randomized trial, perioperative azithromycin use increased markedly among cesarean births. In adjusted difference-in-differences analysis, postpartum infection declined by 2.0 percentage points for cesarean births relative to vaginal births.

Why it matters

This is large-scale evidence that the benefit seen in the original clinical trial appears to translate into routine U.S. practice. It strengthens the implementation case for adjunctive azithromycin in patients undergoing an unscheduled cesarean after labor or membrane rupture when otherwise appropriate.

What to do now: This study does not create a new indication. ACOG Practice Bulletin No. 199, reaffirmed in 2025, already includes adjunctive azithromycin among cesarean infection-prevention practices. Hospitals should confirm that current cesarean prophylaxis protocols reflect their adopted ACOG-based criteria, dosing, allergy pathways, and antimicrobial-stewardship policies.

Why this belongs in the update

Strong implementation evidence supporting an established practice rather than a new standard of care.

Primary source: Freret TS, Litman E, Wen T, et al. Adoption of Adjunctive Azithromycin for Unscheduled Cesarean Delivery and Postpartum Infections. JAMA. Published online September 14, 2026. doi:10.1001/jama.2026.15010. Current guideline context: ACOG Practice Bulletin No. 199: Use of Prophylactic Antibiotics in Labor and Delivery (reaffirmed 2025).

CDC seasonal guidance · Respiratory immunization

Update pregnancy vaccine counseling for the 2026–27 respiratory-virus season

USE NOW

What changed

CDC posted 2026–27 COVID-19 vaccine guidance on September 23, 2026, and updated its 2026–27 influenza-season information on September 29. CDC's current influenza clinical guidance continues to recommend inactivated or recombinant influenza vaccine during pregnancy and not live-attenuated influenza vaccine. The seasonal maternal RSV recommendation remains one dose of Pfizer Abrysvo at 32 weeks 0 days through 36 weeks 6 days during the recommended seasonal window in most of the continental United States.

Why it matters

September and October are the main implementation period for seasonal influenza vaccination. Pregnancy also increases the risk of severe COVID-19. Respiratory-season counseling should use the current-season CDC schedule rather than older vaccine-season language.

What to do now: Review the office vaccine handout and standing counseling language for influenza, COVID-19, and maternal RSV. Keep product, age, seasonal, and interval details synchronized with current CDC guidance because these can change between seasons.

Related Perinatology.com resource

Vaccines in Pregnancy

Primary sources: CDC 2026–27 COVID-19 vaccine guidance ; CDC 2026–27 influenza season ; CDC influenza clinical considerations ; CDC maternal RSV guidance .

SMFM Statement · Red-cell alloimmunization · Published July 2026

Clarify the role of cfDNA fetal red-cell antigen genotyping

REVIEW WORKFLOW

What the 2026 statement clarifies

SMFM states that routine cfDNA fetal RhD genotyping is not currently recommended for nonalloimmunized patients when Rh immune globulin is readily available, and it is not recommended in multifetal pregnancy because of insufficient data. For alloimmunized patients, amniocentesis remains the standard diagnostic approach when fetal antigen status must be determined, although cfDNA testing can be considered after counseling when diagnostic testing or empiric HDFN surveillance is declined.

Why it matters

Fetal antigen status can determine whether an alloimmunized pregnancy needs ongoing HDFN surveillance. The statement helps prevent a screening test from being substituted automatically for established diagnostic testing, antibody titer interpretation, or MCA Doppler surveillance.

What to do now: Cross-check the Rh disease and red-cell alloimmunization workflow so cfDNA fetal antigen testing is presented as an option only in the settings supported by the SMFM statement. Critical titers, prior affected pregnancies, and MCA PSV surveillance should continue to follow established alloimmunization guidance.

Related Perinatology.com resources

Rh disease and red-cell alloimmunization MCA PSV calculator MCA PSV twins calculator

Primary source: SMFM Statement: Evaluation and management of red cell alloimmunization in pregnancy using cell-free DNA fetal red cell antigen genotyping (2026) . This statement was first published July 1, 2026 and is included here as an implementation follow-up because of its direct relevance to Perinatology.com alloimmunization and MCA Doppler resources.

SMFM Special Statement · Ultrasound infection prevention

Updated infection-control guidance now includes transabdominal and invasive ultrasound procedures

USE NOW

What changed

SMFM updated its 2020 transvaginal-ultrasound infection-prevention statement. The 2026 version expands the scope to transabdominal examinations, ultrasound-guided percutaneous procedures, and intraoperative procedures. It also discusses newer high-level disinfection systems and updated evidence on disinfectant activity against HPV.

Why it matters

Ultrasound equipment can transmit infection when cleaning, disinfection, probe-cover, or coupling-gel practices are inconsistent. The broader guidance is directly relevant to outpatient MFM ultrasound units as well as procedure areas.

What to do now: Compare written ultrasound cleaning, disinfection, probe-cover, and gel policies with the updated statement, including protocols for transabdominal and invasive procedures.

Perinatology.com impact

No calculator change identified. Consider a concise ultrasound infection-control reference for MFM offices.

Primary source: SMFM Special Statement: Reducing the risk of transmitting infection during ultrasound examination—Updated 2026

SMFM Special Statement · Maternal critical care

Updated checklist for the initial management of amniotic fluid embolism

USE NOW

What changed

SMFM updated its 2021 AFE checklist. The revised cognitive aid aligns terminology with current advanced cardiac life support guidance and includes recommendations for local implementation. A correction published after the initial release updated dosage units for several vasoactive medications in the figure.

Why it matters

AFE is rare and rapidly life-threatening. Because individual clinicians may encounter it only rarely, a current, rehearsed cognitive aid can support a coordinated response.

What to do now: Replace older AFE checklists in labor and delivery emergency materials, verify that the corrected version is used, and incorporate it into multidisciplinary simulation drills.

Related Perinatology.com resource

Pulmonary disorders in pregnancy

Primary source: SMFM Special Statement: Checklist for initial management of amniotic fluid embolism—Updated 2026

SMFM Special Statement · Fetal cardiology quality

Updated quality metrics for prenatal detection of congenital heart defects

REVIEW WORKFLOW

What changed

SMFM updated its 2020 quality metrics for prenatal congenital heart defect detection. The revised approach incorporates the O35.BXXn family of ICD-10-CM codes for fetal cardiac anomalies and discusses remaining limitations in linking maternal fetal records with newborn records.

Why it matters

SMFM notes that fewer than half of congenital heart defects are detected prenatally. Consistent measurement of detection rates can support quality-improvement programs and help identify gaps in imaging, referral, and documentation.

What to do now: Practices tracking fetal cardiac detection should review coding and maternal-newborn record linkage and determine whether the updated metrics can be implemented locally.

Related Perinatology.com resources

Fetal Echocardiogram Z Score Calculator 2

Primary source: SMFM Special Statement: Quality metrics to assess prenatal detection of congenital heart defects—Updated 2026

SMFM Special Statement · Sickle cell disease

New checklists span the full pregnancy episode and vaso-occlusive crisis care

REVIEW WORKFLOW

What changed

SMFM published checklists for prepregnancy, antepartum, delivery, postpartum, and vaso-occlusive crisis management in patients with sickle cell disease. The statement emphasizes integration into clinical workflows and ongoing quality review.

Why it matters

Sickle cell disease in pregnancy requires coordinated obstetric, MFM, hematology, nursing, and hospital care. Structured checklists can reduce omissions across multiple transitions of care.

What to do now: Compare existing sickle cell pregnancy order sets and protocols with the new SMFM checklists and ensure the vaso-occlusive crisis pathway is readily available in both outpatient and inpatient settings.

Related Perinatology.com resource

Hematologic disorders in pregnancy

Primary source: SMFM Special Statement: Checklists for persons with sickle cell disease in pregnancy

New research · Not independently practice changing

Watching

AJOG Research Letter · Amniotic fluid embolism

A cytokine storm may precede the clinical collapse of amniotic fluid embolism

WATCHING

What was observed

Romero and colleagues analyzed stored maternal plasma from a patient who appeared asymptomatic at admission but later developed disseminated intravascular coagulation and cardiopulmonary collapse consistent with amniotic fluid embolism. The pre-event sample showed extraordinarily high concentrations of several inflammatory cytokines, including IL-6, IL-8, IL-10, and TNF-alpha.

Why it is intriguing

The finding supports the concept that at least some cases of amniotic fluid embolism may involve a severe inflammatory response that begins before the classic clinical syndrome becomes apparent. If confirmed prospectively, this could eventually influence how AFE is understood, detected, or treated.

What to do now: No screening test, cytokine threshold, preventive treatment, or early-treatment protocol can be recommended from this report. The observation comes from a single fatal case and requires prospective validation before cytokine measurement can be considered clinically useful for predicting AFE.

Why this belongs in “Watching”

Potentially important pathophysiologic insight, but hypothesis-generating rather than practice changing.

Primary source: Romero R, Meyyazhagan A, Gudicha DW, et al. A subclinical cytokine storm is present before the clinical diagnosis of amniotic fluid embolism: implications for the prediction and prevention of maternal death. Am J Obstet Gynecol. 2026;235(1):e3-e6. doi:10.1016/j.ajog.2026.02.039.

Expert review · Fetal growth restriction

Updated comparison highlights agreement and disagreement across major FGR guidelines

WATCHING

What the review found

A September 2026 AJOG review compared six national and international FGR guidelines. There was broad agreement on Doppler-based surveillance and standard interventions for anticipated preterm birth, but important differences remained in FGR definitions, growth charts, ductus venosus use, biophysical profile use, angiogenic biomarkers, and delivery approaches.

Why it is useful

The review provides a concise way to identify where an SMFM-based U.S. workflow agrees with other societies and where recommendations diverge because evidence or practice context differs.

What to do now: Use the review as a cross-check when maintaining FGR content, but do not merge conflicting society recommendations into a single rule without clearly identifying the source framework.

Related Perinatology.com resources

FGR / selective FGR wizard Umbilical artery Doppler

Primary source: Di Mascio D, et al. Consensus and controversies of international guidelines for the diagnosis, surveillance, and management of fetal growth restriction: an updated comparison. Am J Obstet Gynecol. 2026;235(3):486-505.

Retrospective cohort · Preeclampsia and FGR

At very high sFlt-1/PlGF ratios, clinical context may matter more than the exact number

WATCHING

What the study did

Investigators studied 132 singleton pregnancies at a tertiary center in which the sFlt-1/PlGF ratio exceeded 600. They examined whether the absolute ratio improved prediction of perinatal death or severe morbidity beyond gestational age and estimated fetal weight.

What they found

Adding the absolute ratio did not improve discrimination for the studied adverse outcomes. A ratio above 600 was associated with shorter time to delivery. In serial measurements, faster ratio rise contributed information for early neonatal death, and lower PlGF was associated with severe morbidity among growth-restricted fetuses.

What to do now: Do not create a new management threshold from this single retrospective study. For extremely abnormal ratios, interpret the result together with gestational age, fetal growth, Doppler findings, maternal status, and the validated clinical use of the assay.

Related Perinatology.com resource

sFlt-1/PlGF clinical workflow

Primary source: Satorres-Pérez E, et al. Extreme sFlt-1/PlGF ratio in preeclampsia and fetal growth restriction: is there prognostic value beyond gestational age and fetal biometry? Pregnancy Hypertens. 2026;46:101510.

Retrospective cohort · Early-onset preeclampsia

Repeated antihypertensive escalation may be a marker of maternal disease progression

WATCHING

What the study did

A single-center retrospective cohort included 396 singleton pregnancies managed expectantly for preeclampsia with severe features from 23 weeks 0 days through 33 weeks 5 days. Investigators examined the relationship between escalating oral or intravenous antihypertensive treatment and maternal outcomes.

What the study found

Maternal adverse-outcome risk increased as the number of antihypertensive escalations increased. Each additional oral dose escalation was associated with an absolute 4.2 percentage-point increase in the composite maternal adverse outcome. Repeated intravenous treatment showed a similar pattern. Neonatal outcomes were not significantly different by escalation category.

What to do now: Do not create a new delivery threshold from this retrospective study alone. During expectant management, however, increasing medication requirements may be a useful dynamic marker of disease progression to consider alongside symptoms, laboratory findings, fetal status, gestational age, and established delivery criteria.

Perinatology.com impact

No calculator or delivery-timing rule change. Consider this evidence when future preeclampsia triage or expectant-management content is revised.

Primary source: Antihypertensive Treatment Escalation and Maternal Outcomes During Expectant Management of Early-Onset Preeclampsia With Severe Features. Am J Obstet Gynecol. 2026.

Clinical disclaimer: This material is for professional education and does not replace clinical judgment, institutional policy, applicable law, or individualized patient care. Clinicians should review the original source before changing management.