The Week in MFM
For patients and families
The biggest news this week is about vaccines during pregnancy. The American College of Obstetricians and Gynecologists released its updated guidance for the upcoming respiratory virus season, recommending flu, COVID-19, and RSV vaccination during pregnancy. The window for the RSV vaccine, which protects newborns from a serious lung infection, is now open from September 1 through March 1, a month longer than before.
Researchers also published new findings on how doctors monitor growth in identical twins, how blood pressure treatment in pregnancy might one day be tailored to each patient's circulation, and why gestational diabetes may look different from one patient to the next. None of these change your care today, but they show where the field is headed. As always, bring questions to your visit; we are happy to walk through any of this with you.
Vaccination guidance leads a quiet week. On September 2, ACOG released its 2026-27 respiratory virus immunization recommendations, extending the maternal RSV vaccination window by a full month, through March 1, and reaffirming COVID-19 and influenza vaccination in any trimester. That single change should reach your standing orders before the season does. The rest of the week's signal came from the September journal issues: a push toward subtype-based thinking in gestational diabetes from Diabetes Care, and two studies in Ultrasound in Obstetrics & Gynecology on risk stratification in monochorionic twins and hemodynamics-guided hypertension management. Prenatal genetics and preterm birth prevention were genuinely quiet; we skip them rather than pad.
1.ACOG's 2026-27 respiratory virus guidance extends the RSV vaccination window to March 1
Released September 2 alongside the Vaccine Integrity Project's evidence review, the guidance strongly recommends COVID-19 vaccination in any trimester, inactivated or recombinant influenza vaccine in any trimester, and bivalent RSVpreF (Abrysvo) at 32-36 weeks, now administered September 1 through March 1 rather than through January 31, reflecting later and more severe RSV seasons. The supporting review found maternal RSV vaccination reduces infant RSV hospitalization by 51-70%, maternal COVID-19 vaccination extends 50-54% protection to infants in their first 2 months, and maternal influenza vaccination is roughly 44% protective for infants 0-6 months. Coadministration of all three is acceptable.
Sources: Contemporary OB/GYN summary · STAT News coverage · Interview on the extended RSV window
2.Diabetes Care pushes GDM toward subtype-based thinking
"Defining Clinical Heterogeneity in Gestational Diabetes Mellitus: The Importance of Timing and Severity of Maternal Hyperglycemia," in the September issue of Diabetes Care (49:1549), argues that GDM is not one disease: timing of onset and degree of hyperglycemia define subgroups with meaningfully different perinatal risk profiles, and uniform management blurs that signal. Full metrics were not accessible this week, so treat the specifics as the authors' framing of the precision-GDM question rather than confirmed effect sizes.
Source: Diabetes Care 49(9):1549
3.In monochorionic twins with sFGR, Doppler classification alone is a weak prognosticator
In the September issue of Ultrasound in Obstetrics & Gynecology, the umbilical artery Doppler classification by itself showed limited ability to predict adverse outcome in the smaller twin of monochorionic pairs with selective fetal growth restriction. Prediction improved substantially when the classification was combined with gestational age at diagnosis, intertwin weight discordance, and estimated fetal weight.
Sources: UOG, DOI 10.1002/uog.70320 · September 2026 UOG Highlights
4.Hemodynamics-guided antihypertensive therapy shows a signal for less FGR and preterm birth
A systematic review and meta-analysis in the September UOG issue found that tailoring antihypertensive therapy to maternal hemodynamic assessment significantly reduced the odds of preeclampsia/eclampsia, fetal growth restriction, severe hypertension, preterm birth, and composite adverse outcomes compared with conventional management. GRADE certainty was low to very low across outcomes.
Sources: UOG, DOI 10.1002/uog.70250 · September 2026 UOG Highlights
Also this week: no substantive new publications in prenatal genetics or in preterm birth prediction and prevention crossed our screen for August 28 to September 3. A quiet week is reported as a quiet week; we do not pad.
Curated for clinicians and the families we care for · Pasadena · Arcadia · Century City · Torrance · La Cañada
This digest summarizes recently published research and guidance; it is not medical advice. Discuss individual care with your physician.
