Understanding the Hormones That Initiate Breastfeeding
How Your Hormones Help Start Breastfeeding
Breastfeeding begins long before your baby is born. Throughout pregnancy and in the moments after delivery, your body goes through a carefully coordinated hormonal shift to prepare your breasts, produce colostrum, and initiate mature milk production. Understanding how these hormones work together can empower parents—especially NICU families—as they begin their feeding journey.
At NEOwell, we believe informed families feel more confident and supported. Here’s a simple, evidence-based look at the hormones that play a role in initiating breastfeeding.
Prolactin: The Milk-Production Powerhouse
Prolactin is the primary hormone responsible for making breast milk. During pregnancy, prolactin levels climb steadily, preparing the breast tissue to produce colostrum. After birth, when the placenta is delivered, progesterone levels drop sharply, removing the hormone that was blocking prolactin from producing larger volumes of milk. This hormonal shift triggers Lactogenesis II, also known as the “milk coming in.”
What supports prolactin?
Frequent breastfeeding or pumping
Nighttime feeds (prolactin peaks at night)
Skin-to-skin contact
Oxytocin: The “Let-Down” Hormone
Oxytocin triggers the milk ejection reflex, often called the let-down reflex. When your baby latches and begins to suck, oxytocin causes the tiny muscles around the milk-producing alveoli to contract, pushing milk down the ducts and out to the nipple.
Oxytocin also promotes maternal–infant bonding and helps reduce postpartum bleeding by encouraging uterine contractions.
Tips to support oxytocin:
Skin-to-skin time
Deep breathing and relaxation
A calm environment
Supportive, encouraging caregivers
NEOwell’s in-home postpartum visits are designed to foster exactly this type of oxytocin-rich environment.
Estrogen & Progesterone: The Pregnancy Prep Team
These two hormones dominate during pregnancy, helping your breasts grow the structures needed for lactation.
Estrogen supports the development of the milk ducts.
Progesterone helps form the alveoli, where milk is produced.
After delivery, the dramatic drop in estrogen and progesterone “releases the brake,” allowing prolactin to produce higher milk volumes. This shift marks the transition from colostrum production to mature milk production.
Human Placental Lactogen: The Bridge Between Pregnancy and Breastfeeding
Human placental lactogen (hPL) is produced by the placenta throughout pregnancy and helps prepare the breasts for milk production. It works alongside prolactin to support colostrum production during late pregnancy. After birth, hPL disappears quickly due to placental delivery, completing the hormonal transition to Lactogenesis II.
Supporting Hormones: Insulin, Thyroid Hormones & Cortisol
While not directly responsible for the let-down reflex or milk production, these metabolic hormones support healthy lactation:
Insulin helps breast cells utilize energy for milk production.
Thyroid hormones maintain normal metabolism and cellular function.
Cortisol supports milk production at normal levels but can inhibit the let-down reflex when significantly elevated due to stress.
Conditions such as hypothyroidism, diabetes, or retained placenta may impact these hormones and affect breastfeeding initiation—something NEOwell can help families navigate with close observation and education.
The Hormonal Timeline of Breastfeeding Initiation
Pregnancy:
High estrogen, progesterone, and hPL prepare the breast; prolactin begins producing colostrum.
Immediately After Birth:
Placental delivery → estrogen & progesterone drop → prolactin rises → milk production increases.
First Days Postpartum:
Frequent feeding drives prolactin surges and shapes long-term milk supply.
Oxytocin initiates and strengthens the let-down reflex.
Milk transitions from colostrum to mature milk between days 2 and 5.
How NEOwell Supports Families in the Early Breastfeeding Journey
Whether you’re navigating a NICU stay, welcoming your first baby, or transitioning home with a preterm infant, NEOwell provides:
Hands-on breastfeeding support
Bottle-feeding and combo-feeding education
Pumping assistance and flange sizing
NICU-to-home guidance
In-home postpartum visits
Personalized feeding plans
We empower families with the knowledge, skills, and confidence needed to build a strong feeding relationship—starting with the hormones that enable breastfeeding.