In a discovery that could shift labor and delivery practices around the world, researchers at Michigan State University have found that the effectiveness of oxytocin—a common medication used to induce or speed up labor—depends on the time of day it’s administered, especially for patients with gestational diabetes.

The study, published in Molecular Metabolism, combined laboratory research in mice and human cells with a retrospective review of more than 2,300 pregnancies.

The results were striking. Women whose labors were induced in the early morning to around noon experienced significantly shorter labor durations than those induced around midnight. For patients with gestational diabetes, the timing difference amounted to as much as seven hours.

“Our findings suggest timing isn’t just about scheduling—it can affect how well a patient’s uterus responds to labor-inducing medication,” said Hanne Hoffmann, associate professor of animal science at MSU and lead author of the study.

The science behind the clock

At the center of the discovery is BMAL1, a key circadian rhythm gene that helps control the body’s biological 24-hour clock. In mice, the researchers showed that BMAL1 helps regulate the oxytocin receptor in the uterus, which is the same receptor that synthetic oxytocin targets to trigger contractions. When the gene was turned off or suppressed, either genetically or through a mouse model of gestational diabetes, oxytocin was significantly less effective at inducing contractions.

“We were able to show that BMAL1 directly controls the oxytocin receptor, which helps explain why time of day changes the drug’s effectiveness,” Hoffmann said. “This is the first study to make that molecular connection in the uterus.”

In human cell experiments, MSU scientists observed a circadian rhythm of contraction responses to oxytocin confirming what had previously only been speculated.

Real-world implications for labor and delivery

The team also analyzed labor and delivery records from Sparrow Health System in Lansing, Michigan, focusing on more than 2,300 patients who were at least 39 weeks pregnant. Labor duration was compared across different time windows of the day and between patients with and without gestational diabetes.

The shortest labors occurred when induction started between 8 a.m. and noon and the longest when induction began between midnight and 4 a.m. This effect was especially dramatic in patients with gestational diabetes, suggesting reduced oxytocin sensitivity during nighttime hours.

“This isn’t about convenience,” Hoffmann said. “It’s about optimizing outcomes. If we can better align medical interventions with a patient’s internal clock, we may improve safety for both mother and baby, while potentially being able to reduce the amount of a drug a woman receives.”

Hoffmann and her team are now expanding their research to a larger cohort to refine the optimal timing of labor induction. “Our ongoing work suggests that factors such as whether a woman has previously given birth and her BMI may further influence oxytocin‘s effectiveness,” Hoffmann explained.

“By integrating these considerations with the time of day of drug administration, we can make labor induction safer, faster and more personalized. These simple, evidence-based steps could significantly improve delivery outcomes, lower the rates of cesarean sections and NICU admissions, and strengthen maternal and neonate recovery.”

The next phase of research will include a prospective study in collaboration with labor and delivery units to develop clear, practical guidelines for obstetricians to optimize induction timing. Ultimately, aligning medical care with the body’s natural rhythms has the potential to enhance not only birth outcomes, but the long-term health and well-being of mothers, babies and families—a cornerstone of a healthy and thriving population.