Recruiting

NCT Number: NCT07720414

Effects of GLP-1 RAs on Human Lactation Outcomes

There is increasing interest in using GLP-1 Receptor Agonist (GLP-1 RA) medications after pregnancy. This study is designed to determine if these medications affect breastmilk production or the nutritional makeup of breastmilk.

The main questions the study will address are:

* Does GLP-1 RA-induced weight loss increase or decrease breastmilk production? * Does GLP-1 RA-induced weight loss affect the nutritional composition of milk, including milk fat content?

Researchers will assess milk production rates before and after mothers begin taking injected GLP-1 RA medications to decrease their body weight. Weight loss will be confirmed with 7-day body weight averages.

Participants will:

* Weigh themselves and report measurements daily. * Participate in 2-3 morning study visits over approx. 2.5-4.5 months (approx. 3-3.5hrs each).

During each visit, participants will:

* Use a study provided breastpump to express milk 3 times hourly for measurement of hourly milk production. * Provide 1-3 oz of milk for further study. * Answer questions about breastfeeding patterns.

Recruiting

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Key information

Conditions

Lactation Behavior Body Weight Body Weight Changes Breast Feeding Feeding Behavior Pathological Conditions, Signs and Symptoms Signs and Symptoms Weight Loss

Sex eligibility

Female

Study type

Observational

Primary location

University of Colorado Anschutz School of Medicine

Aurora, Colorado, 80045, United States

Location status: Recruiting

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

Breastfeeding mothers of single or multiple infants.
Milk removal at least 4x daily
Eligible for a GLP-1 RA administered subcutaneously (oral GLP-1 RAs contain absorption enhancers, which may drive accumulation in milk)
Access to a breastpump, if needed for maintaining breastfeeding behaviors.
Willingness to provide 1-3 oz of breastmilk per study visit.
Willingness to track and report body weight daily.
Willingness to maintain breastfeeding behaviors for the duration of the study.

Exclusion criteria

Currently taking GLP-1 RA medication or other weight loss medication
Induced lactation, due to unknowns regarding the durability of the mammary gland's milk production after exogenous stimulation.

Treatment and study plan

Injected GLP-1 Receptor Agonists and Dual Agonists

Drug

Participants are prescribed this medication by their care provider(s) as part of their postnatal clinical care, including but not limited to semaglutide and tirzepatide. The investigators do not provide, manage, or assign the medication.

Primary outcomes

Hourly milk production rate

Time frame: From one week before until a maximum of 2 months after beginning GLP-1RA treatment. This timeframe will restart if their dosage is increased.

Milk production rate (in grams per hour) will be assessed using a standardized milk expression protocol.
Milk macronutrient composition

Time frame: From one week before until a maximum of 2 months after beginning GLP-1RA treatment. This timeframe will restart if the dosage is increased.

Milk macronutrient composition will be assessed using the Miris Human Milk Analyzer.

Study contacts

Contact information is provided by the study sponsor or research team.

Jacinda M Nicklas, MD, MPH

CONTACT

[email protected]

303-724-9028

Jayne F Martin Carli, PhD

CONTACT

[email protected]

303-724-3981

Sponsors and collaborators

Lead sponsor

University of Colorado, Denver

Other

Registry information

Important dates

Study start: 2026
Primary completion: 2028
Study completion: 2028
First posted: Jul 22, 2026
Registry last updated: Jul 22, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

Published trials that share one or more normalized conditions with this study.

Recruiting