Beyond the Love Hormone: What Oxytocin Really Does in Birth, Bonding, and Fertility

“Oxytocin is often called ‘the love hormone’. Its real job is much bigger than that. It is made in the brain. It helps drive labour and breastfeeding, and it shapes the bond between mother and baby. Recent studies also ask whether it affects IVF success and male fertility. This article explains what oxytocin is, how it works in reproduction, and what new research shows for people trying to conceive.

What is oxytocin?

Oxytocin is a small hormone built from nine amino acids. The hypothalamus, a control centre deep in the brain, makes it. The posterior pituitary gland then releases it into the blood (Uvnäs-Moberg, 2024; Winokur et al., 2025). A 2026 study in mice mapped where oxytocin and its receptor sit in the brain (Ryu et al., 2026).

Its best-known jobs:

• It triggers the uterus to contract during labour.
• It helps release milk during breastfeeding.
• It supports bonding, trust, and calm. This is why people call it the ‘love hormone’ (Winokur et al., 2025).

Scientists now see oxytocin as more than a (love) signal. Winokur et al. (2025) described the nickname as inaccurate. Walle et al. (2026) argued that oxytocin helps people adapt their behaviour to many situations, both social and non-social.

How does oxytocin work in reproduction?

Oxytocin takes part in several key steps of pregnancy and birth:

• During labour, the body releases oxytocin in pulses. It binds to oxytocin receptors on the muscle of the uterus and sets off contractions (Uvnäs-Moberg, 2024).
• Near the end of pregnancy, high estrogen makes these receptors more sensitive. The uterus then responds strongly at the right time (Uvnäs-Moberg, 2024).
• After delivery, doctors often give a dose of oxytocin. It tightens the uterus, which helps the placenta separate and prevents heavy bleeding (Uvnäs-Moberg, 2024).

Oxytocin also works inside the brain during birth. It is thought to ease fear, pain, and stress, and it supports the early bond between mother and baby (Uvnäs-Moberg, 2024; Winokur et al., 2025).

Does oxytocin affect IVF and embryo implantation?

Here, the fertility research gets interesting. The uterus makes gentle contractions of its own. In a study of 68 women having a frozen embryo transfer, those with fewer contractions in the hour before the transfer were more likely to become pregnant than those with frequent contractions (Javedani Masroor et al., 2023).

Doctors have tested a drug called atosiban. It blocks the oxytocin receptor and calms these contractions. The results so far are mixed:

• A large trial of 1,100 women, published in 2025, found no clear rise in live births with atosiban (Cai et al., 2025). All of these women had failed one earlier transfer. Among the 163 with abnormal contractions, live births were higher with atosiban (51.9% against 39.3%), but the gap was not statistically significant.
• A smaller trial in women having frozen embryo transfers reported a higher clinical pregnancy rate with atosiban than without it (58% against 38%) (Arora et al., 2025). Because the trial was small, the result needs confirming.
• In women with adenomyosis, tissue from the womb lining grows into the uterine wall. A 2024 study compared 168 treated women with 168 matched women. Early miscarriage was lower in the treated group, but pregnancy and live birth rates did not differ overall (Lin et al., 2024).

Put together, these studies give a cautious message. Blocking oxytocin may help some women, especially those whose uterus contracts too much, but it does not appear to help everyone (Cai et al., 2025; Moliner et al., 2026). The Moliner report was a conference poster, so its findings are still early.

What about men and oxytocin?

Oxytocin works in male reproduction too:

It takes part in erection and ejaculation (Dale et al., 2024).

A 2026 review of animal studies found that oxytocin given as a nasal spray activated brain pathways and improved sperm quality (Sakamoto et al., 2026).

These findings come from animals. Human evidence is still limited.”

Written by Mazen Al-Obaidi

Assistant Professor, University of Technology and Applied Sciences

References

Title: A Randomised Controlled Trial to Study the Efficacy of Administration of Atosiban Before Embryo Transfer on In Vitro Fertilisation

Authors: Aashna Arora, Kanad Dev Nayar, Sabina Sanan, Manika Sachdeva, Gaurav Kant, Ananya Singh, Meetakshara Singh

You can read the Full Article in Fertility Science and Research.

Title: Atosiban in individuals with previous implantation failure undergoing frozen blastocyst transfer: a randomized controlled trial

Authors: He Cai, Shan Liu, Wentao Li, Haiyan Bai, Hanying Zhou, Xia Xue, Wei Li, Mingzhao Li, Xiaoli Zhao, Chun Ma, Hui Wang, Li Tian, Tao Wang, Na Li, Jinlin Xie, Lijuan Chen, Min Wang, Chen Yang, Hua Jia, Dian Zhang, Danmeng Liu, Ben W Mol, Juanzi Shi

You can read the Full Article in Human Reproduction.

Title: From Parental Behavior to Sexual Function: Recent Advances in Oxytocin Research

Authors: Joseph Dale II, Mitchell T. Harberson, Jennifer W. Hill

You can read the Full Article in Current Sexual Health Reports.

Title: The Effect of Uterine Contractions on Fertility Outcomes in Frozen Embryo Transfer Cycles: A Cohort Study

Authors: Mojgan Javedani Masroor, Ladan Younesi Asl, Niloufar Sarchami

You can read the Full Article in the Journal of Reproduction and Infertility.

Title: Improvement of early miscarriage rates in women with adenomyosis via oxytocin receptor antagonist during frozen embryo transfer-a propensity score-matched study

Authors: Po-Wen Lin, Chyi-Uei Chern, Chia-Jung Li, Pei-Hsuan Lin, Kuan-Hao Tsui, Li-Te Lin

You can read the Full Article in Reproductive Biology and Endocrinology.

Title: L26/P-551 Atosiban improves implantation rates in patients with elevated uterine contractility: a counterfactual analysis at different UC thresholds

Authors: B. Moliner, L.S. Gorgan, A. Herencia Rivero, G. Bertapelle, C. Quetglas Muñoz, V. Legidos Lopez, A. Bernabeu García

You can read the Full Article in Human Reproduction.

Title: Single transcript level atlas of oxytocin and the oxytocin receptor in the mouse brain

Authors: Vitaly Ryu, Anisa Azatovna Gumerova, Georgii Pevnev, Funda Korkmaz, Hasni Kannangara, Liam Cullen, Farhath Sultana, Ronit Witztum, Steven Lee Sims, Tal Frolinger, Ofer Moldavski, Orly Barak, Emily Weiss, Jay J Cao, Daria Lizneva, Ki A Goosens, Tony Yuen, Mone Zaidi

You can read the Full Article in eLife.

Title: Oxytocin Neuropharmacology: From Brain to Sperm

Authors: Hirotaka Sakamoto, Chica Enomoto, Takumi Oti

You can read the Full Article in Current Neuropharmacology.

Title: The physiology and pharmacology of oxytocin in labor and in the peripartum period

Authors: Kerstin Uvnäs-Moberg

You can read the Full Article in the American Journal of Obstetrics and Gynecology.

Title: Reframing oxytocin as a behavioral flexibility hormone

Authors: Kjersti M. Walle, Alina I. Sartorius, Elisabeth Deilhaug, Heemin Kang, Terje Nærland, Ole A. Andreassen, Lars T. Westlye, Daniel S. Quintana

You can read the Full Article in Neuroscience and Biobehavioral Reviews.

Title: Oxytocin

Authors: Sarah B. Winokur, Asha Y. Caslin, Felicity M. Davis, Robert C. Froemke

You can read the Full Article in Current Biology.

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