Breastfeeding is a complex process, guided by several hormones working together in a beautifully coordinated way. These hormones help prepare your body during pregnancy, support breast milk production after birth, and influence how breastfeeding feels—physically and emotionally.

Understanding what’s happening hormonally can offer reassurance, normalize what you’re experiencing, and help you feel more supported as you feed your baby.

How Do Hormones Prepare Your Body for Breastfeeding?

Your body begins preparing for breastfeeding long before your baby arrives. You may notice breast growth, tenderness, or darkening of the areolas. By the second trimester, as early as 16 weeks of pregnancy, your breasts begin producing colostrum—a thick, nutrient-rich early milk that will be your baby’s first food.

Two key hormones—estrogen and progesterone—guide this preparation and set the stage for future milk production.

Estrogen

Estrogen plays an important role in reproductive development and breast changes during puberty and early pregnancy. During pregnancy, rising estrogen levels help stimulate the growth and branching of the milk ducts within the mammary glands. This ductal growth creates the pathways that will later carry milk to your baby.

Progesterone

Progesterone works alongside estrogen during pregnancy to prepare the breasts for milk production. It supports the development of the alveoli—the milk-producing glands inside the breast. High levels of progesterone during pregnancy prevent larger volumes of milk from being released before birth. Once your baby is born and the placenta is delivered, progesterone levels drop sharply. This shift is essential—it signals your body that it’s time to begin making larger volumes of milk.

  • This is one of the fastest hormonal shifts your body will ever experience. While it’s completely normal and necessary, it can feel intense.

  • Many mothers notice tearfulness at unexpected times, emotional sensitivity, or feeling overwhelmed—often referred to as the "baby blues."

  • These feelings often ease after the first few days and usually fade by around two weeks postpartum.

Postpartum Hormonal Shift

The hormonal changes that occur after birth affect not only milk production, but also mood, energy, and emotional well-being—especially for new mothers caring for a newborn baby. Your breastfeeding hormones respond to your baby’s cues—like when your baby suckles, when you hear your baby cry, or even when you use a breast pump. One of the most influential of these postpartum hormones is prolactin.

Prolactin Surge

When estrogen and progesterone levels drop after birth, prolactin levels rise. This surge in prolactin triggers the increase in milk volume—often called “milk coming in”—which typically occurs around Days 3–5 postpartum.

Frequent breastfeeding or pumping helps prolactin receptors develop, signaling your body to make enough milk and regulate the amount of milk your baby needs over time. You may also notice physical sensations, such as uterine contractions during early feedings or night sweats and hot flashes, as your body adjusts.

Prolactin also affects how you feel. Many mothers describe a sleepy, calm, or foggy sensation during feedings. This hormonal state can support rest and recovery—but for some, it may feel disconnecting or emotionally flat.

Oxytocin

Another key hormone in breastfeeding is oxytocin—often called the “love hormone.” Oxytocin is released during breastfeeding, skin-to-skin contact, and close interactions with your baby. It’s responsible for the "letdown reflex" (or milk ejection reflex) and plays a major role in emotional bonding.

The release of oxytocin is closely tied to your emotional environment. When oxytocin levels rise, milk flows more easily and feelings of closeness and connection are supported. Feeling calm, safe, supported, and comfortable helps this process work more smoothly. Stress, pain, fear, feeling rushed, or feeling watched can interfere with this process.

This is why breastfeeding or pumping often feels easier when you’re emotionally supported and physically comfortable.

Stress Hormones

It’s also important to acknowledge stress hormones—especially cortisol levels and adrenaline. 

These hormones increase when you’re overtired, anxious, in pain, or under pressure. While stress hormones do not stop milk production, they can temporarily slow milk flow by interfering with the letdown reflex. This can make feedings feel tense or frustrating and may create a cycle where stress makes feeding harder, and feeding adds more stress.

That cycle is not a failure—or a sign you’re doing anything wrong. It’s a signal that more support, rest, comfort, and reassurance are needed—and that your body is responding exactly as it was designed to.

Breastfeeding Hormones and Your Menstrual Cycle

While breastfeeding, it’s very common for your period to be absent or delayed for many months. This is your body’s natural way of prioritizing milk production. The same breastfeeding hormones that help you nourish your baby also temporarily suppress ovulation and fertility—especially when you’re breastfeeding exclusively.

Everyone’s experience is different, but research shows that most mothers who exclusively breastfeed will go at least 4–6 months without a period, and sometimes much longer. If you’re mixed or combo feeding, or primarily pumping instead, your cycle may return sooner—especially if there are longer stretches between milk removals. 

Also keep in mind, fertility can return even before your first period. If you’d like to avoid closely spaced pregnancies, it's important to find a birth control option that fits your needs and goals.

Birth Control and Breastfeeding

There are several birth control options that are considered compatible with breastfeeding. Breastfeeding friendly options include:

  • Barrier methods (such as condoms)

  • The copper IUD

  • Progestin-only hormonal contraceptives

  • Fertility awareness methods, including Natural Family Planning 

Combined hormonal contraceptives (estrogen + progestin) are generally not recommended during breastfeeding, as estrogen can reduce milk supply.

We have more detailed information in our Birth Control and Breastfeeding Care Guide.

Support During This Transition

Your breastfeeding hormones are doing an incredible amount of work behind the scenes—supporting milk production, bonding, recovery, and your emotional transition into motherhood. If you need help, don't hesitate to reach out to your healthcare provider or lactation consultant for support. Rest, reassurance, and gentle guidance can make a meaningful difference in your postpartum recovery and your feeding journey. You don’t have to navigate this alone.

Disclaimer: Our classes and accompanying materials are intended for general education purposes and should not replace medical advice. For personalized recommendations, please consult your healthcare provider and/or lactation consultant.