Dr. Chapa’s Clinical Pearls

Episode: Vit D and PTB (“New” Feb 2025 Data?)
Date: March 3, 2025
Host: Dr. Chapa

Overview

In this engaging episode, Dr. Chapa delves into the evolving science and clinical controversies around Vitamin D supplementation and its association with preterm birth (PTB). The discussion tracks the historical and current guidelines, major studies (including hot-off-the-press Feb 2025 data), and practical takeaways for OB providers and learners. Dr. Chapa provides both the data and nuanced clinical interpretation, ultimately challenging traditional stances and advocating for pragmatic, patient-centered vitamin D practices.

Key Discussion Points & Insights

1. Opening Anecdote & Vitamin D’s Public Perception

• Playful start referencing the “Sunny D” commercial, highlighting misconceptions about Vitamin D in foods (00:12).
• “The power packed taste of Sunny D contains 5% juice... What the heck is the rest of the 95?” (A, 00:22)
• Sets up that while Vitamin D is often associated with fortification and bones, its role is much broader.

2. Preterm Birth: Still an OB Challenge

• Preterm birth remains a primary clinical challenge, especially since the decline in progesterone use.
• Emerging research into muscarinic receptor blockage for preterm labor—exciting, but still bench science (01:56).
• The question of whether Vitamin D supplementation, especially before pregnancy, could be a simple way to impact PTB rates (03:45).

3. Modern Understanding of Vitamin D

• Vitamin D is not just about bones—it's an immune modulator, inflammatory mediator, and a potential marker for overall wellness (04:32).
• Its roles in pregnancy go far beyond what most guidelines have traditionally acknowledged.

“Vitamin D gets all the attention for bone stability, man... but it’s a very important micronutrient that’s a marker—one potential marker—of overall body wellness.” (A, 04:34)

4. The Controversy: Guidelines vs. Evolving Evidence

a) ACOG’s Stance

• Committee Opinion 495: First published 2011, reaffirmed without significant update in 2024.
  • Briefly: No routine vitamin D supplementation in pregnancy beyond prenatal vitamins pending more definitive trials.
  • “There is insufficient evidence to recommend vitamin D supplementation for the prevention of preterm birth or preeclampsia.” (A, quoting ACOG, 13:23)
• Dr. Chapa finds this outdated and ripe for revision given accumulating data (“That needs to change, okay? That is outdated.” 06:03).

b) Endocrine Society Updates (Aug 2024)

• Clinically recommends supplementation for:
  1. Children
  2. Adults over 75
  3. Adults with pre-diabetes
  4. Pregnant women (08:25)
• This supports Vitamin D importance in pregnancy, despite ACOG’s caution.

c) SMFM and Obstetric Societies

• 2018 SMFM “Do’s and Don’ts”:
  • Vitamin D deficiency “is associated with several adverse outcomes such as preterm birth and preeclampsia, but it is currently unknown whether supplementation improves outcome.” (23:35)
• 2020 Current Opinions in OB/GYN Review: Summarizes recent evidence from intervention studies and meta-analyses.

  “Recent evidence... support vitamin D supplementation during pregnancy to improve maternal, fetal and immediate and later offspring health.” (28:40)

• 2023 SMFM Poster Presentation:
  • Early pregnancy Vitamin D deficiency may increase risk of neonatal respiratory distress, sepsis, and developmental delay in otherwise low-risk women (30:16).

5. What Level Defines “Low” Vitamin D?

• Different societies use different thresholds.
• U.S. practice commonly defines deficiency as <20 ng/mL of serum 25-hydroxy vitamin D (11:11).
  • Equivalent to <50 nmol/L (“They defined vitamin D deficiency or insufficiency as less than 50 nmol/L… this basically… is the same as the 20 ng/mL.” 33:29)

6. Major Studies Leading Up to 2025

a) Meta-Analysis (Nutrients, 2016)

• Vitamin D deficiency is associated with increased risk of preterm birth (PTB).
  • Odds Ratio: 1.29 (CI: 1.16–1.45), which is “not very impressive at all” (20:00).
• Dr. Chapa’s interpretation: Yes, increased risk, but modest, and clinical significance is debatable.

b) SMFM Data (2023)

• Vitamin D deficiency in early pregnancy may be linked to neonatal RDS, sepsis, and developmental delay, even in low-risk patients.

c) 2020 Review in OB/GYN

• Suggests meaningful perinatal and childhood health benefits from supplementation, including possible prevention of ADHD and enamel problems.

7. The Latest (Feb 2025): American Journal of Clinical Nutrition

Publication Highlight:

• Maternal vitamin D status, fetal growth patterns and adverse pregnancy outcomes in a multisite prospective cohort study (Beck et al.)
• U.S. multicenter, prospective cohort of 351 nulliparous women; measured 25OHD at 6–13 and 16–21 weeks.

Key Findings:

• Low first-trimester vitamin D (<20 ng/mL / <50 nmol/L):
  • Associated with linear fetal growth impairment
  • “Low first trimester 25OHD is associated… with a higher risk of preterm birth.” (34:20)
• Second-trimester vitamin D was NOT associated with these outcomes.

“How you enter this race, how you’re conditioned and how your body is ready determines how this is going to go. It seems to be how you enter pregnancy with vitamin D levels is going to be your biggest risk here, not only for neonatal growth trajectory but also for preterm birth.” (A, 36:10)

Clinical Takeaway:
Preconception or early pregnancy vitamin D status, not later supplementation, appears to be most predictive of improved perinatal outcomes, including PTB risk.

Notable Quotes & Memorable Moments

• “If it could possibly help, why not?” (Various points, Dr. Chapa’s practical philosophy)
• “Why not maximize this? … My take is, again, why not just get back to better homeostasis anyway?” (16:44)
• “Pregnancy is a marathon… If you enter the race unconditioned, it’s going to get you… That’s my point.” (30:52)
• “Can it help? Absolutely. And can it hurt? Doesn’t seem to.” (08:13)
• “Recent evidence from vitamin D intervention studies and meta-analyses of a large number of studies support vitamin D supplementation during pregnancy…” (Current Opinions OB/GYN, quoted at 28:40)

Practical Clinical Pearls

• Vitamin D is essential and plays multiple roles (not just skeletal) in pregnancy, including immune and inflammatory modulation.
• Routine supplementation is justified by low risks and potential broad benefits.
• Early (preconception or first trimester) assessment and correction of vitamin D status may meaningfully lower risk of preterm birth and improve fetal outcomes.
• Guideline lag: Some major society recommendations (ACOG) are likely behind the evidence curve and due for revision.

Quick Reference Timestamps

• Sunny D anecdote & Vitamin D intro: 00:12–03:20
• ACOG position & Endocrine Society update: 06:00–09:00
• Vitamin D physiology, serum levels & dosage: 10:02–13:48
• 2016 meta-analysis odds ratio critique: 18:00–21:00
• SMFM & Obstetric society statements: 23:00–24:45
• Current Opinions OB/GYN 2020 review: 28:00–29:00
• 2023 SMFM poster & prelude to Feb 2025 data: 30:00–32:30
• Feb 2025 multisite prospective cohort results: 33:29–36:20
• Final takeaways & “Clinical Pearl” summary: 36:10–end

Bottom Line

This episode cogently argues that early optimization of vitamin D status in women entering pregnancy is a low-risk intervention with growing evidence for improved outcomes (including preterm birth). Dr. Chapa encourages clinicians to remain practically proactive, consider preconception and early pregnancy screening, and not wait for guideline catch-up—because it “can’t hurt, and may help a lot.”