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QUESTO HEALTHCARE ECOSYSTEM Clinical Pharmacology & Maternal-Fetal Drug Safety Center

Document ID: Q-PREG-5094065E

Date Issued: October 07, 2026

Regulatory Base: US FDA (PLLR 8.1/8.2) & NIH LactMed®

Verified Portal: questocomm.com/pregnancy-safety/atenolol

OFFICIAL CLINICAL MONOGRAPH

ATENOLOL

Evidence-Based Medication Safety Profile for Maternal & Lactation Practice

Pregnancy & Lactation Center

Clinical Monograph Beta-1 Selective Adrenergic Antagonist (Beta Blocker)

Human Data Available

Atenolol

UNII Code 50VV3VW0TI

CAS Registry 29122-68-7

RxNorm CUI 1202

Historical FDA Category D

Prescribing & Clinical Reference: Compiled from official regulatory labeling (US FDA PLLR, NIH LactMed®, EMA). Clinical decisions during pregnancy and lactation require individualized patient assessment and physician consultation.

1. Pregnancy Evidence & Regulatory Labeling

FDA Pregnancy and Lactation Labeling Rule (PLLR 8.1) & EMA SmPC Section 4.6

Clinical Risk Summary

Avoid in Pregnancy / Intrauterine Growth Restriction (IUGR). Atenolol is uniquely associated with marked fetal growth restriction, low placental weight, and neonatal hypoglycemia/bradycardia compared to other beta blockers. ACOG and international hypertension guidelines recommend avoiding atenolol in pregnancy and selecting Labetalol or Nifedipine ER.

Human Pregnancy Experience & Clinical Studies

Prospective randomized trials in pregnancy hypertension demonstrated significantly lower birth weight and smaller placental mass with atenolol than with placebo or alternative antihypertensives.

Animal Reproductive & Developmental Toxicity Data

Animal studies demonstrated embryotoxicity and decreased fetal weight.

Clinical Considerations for Prescribers

If a patient presents on atenolol, transition to Labetalol or Nifedipine ER. Perform serial growth ultrasounds every 3-4 weeks.

Placental Transfer

Crosses the placenta readily with cord-to-maternal ratio >1.0.

2. Lactation & Breastfeeding Safety

NIH / NLM LactMed® Database & FDA Labeling Section 8.2

Summary of Use during Lactation

Atenolol concentrates heavily in human breast milk (milk-to-plasma ratio ~1.5 to 6.8) and is excreted primarily by the infant kidneys. Risk of neonatal beta-blockade (bradycardia, hypotension, cyanosis). Preferred alternatives during lactation include Labetalol, Propranolol, or Metoprolol.

Drug Levels in Breast Milk & Relative Infant Dose

Relative Infant Dose (RID) 6.6% – 19% (High, often exceeds 10% safety limit) RID <10% is generally considered low by clinical guidelines.

Milk Concentration & Transport

High concentration in breast milk; milk levels may be several times higher than maternal plasma.

Effects in Breastfed Infants & Monitored Signs

Reported cases of infant bradycardia, cyanosis, and lethargy.

Effects on Lactation & Milk Production

No effect on milk production.

Alternate Medications with Established Lactation Data

Labetalol Propranolol Metoprolol

4. Regulatory Source Provenance & Comparison

Direct attribution to official regulatory documents without synthesized consensus

Regulatory Organization	Jurisdiction	Document / Framework	Effective Date	Official Source Link
National Institutes of Health (NIH) / NLM LactMed® Database (Drugs and Lactation)	United States / Global	evidence_monograph	2026-08-01	Official Record

National Institutes of Health (NIH) / NLM LactMed® Database (Drugs and Lactation)

United States / Global

Framework: evidence_monograph

Effective Date: 2026-08-01

View Official Regulatory Record

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OFFICIAL CLINICAL NOTICE: This monograph is compiled from official U.S. FDA Prescribing Information (PLLR 21 CFR 201.57 Section 8), NIH / NLM LactMed®, and EMA Summary of Product Characteristics (SmPC 4.6). This document is intended solely for reference by licensed healthcare professionals and does not supersede individualized clinical judgment.