The Science of Breastfeeding: How Moms’ Bodies Make Milk

You are not alone if you feel like your body has morphed into one giant mystery through the pregnancy and birthing process. However, the surprises don’t stop there! Post labor and delivery, your body continues to respond to the beautiful journey of motherhood. We understand the confusion and uneasiness for new moms and are here to break down the science of breastfeeding. New moms should read on to understand how and why their bodies are changing. 

Changes During Pregnancy

Women’s bodies prepare to make breast milk months before the baby is even born. Sore breasts are one of the first signs that indicate a woman may be pregnant as they prepare for milk production. When a new mom gets pregnant, hormones cause milk ducts and alveoli to grow.

Hormones like estrogen and progesterone are released by the placenta throughout pregnancy to ensure adequate amounts of breast milk. Additionally, these hormones are carefully measured and released by your brain so you don’t make too much milk before your baby arrives. Colostrum, the first milk your baby feeds on after birth, is created in the second trimester of pregnancy.

Breast Milk After Delivery

Moms’ bodies naturally make more milk to ensure their hungry newborn has enough to eat. The hormones that help increase the number of milk ducts during pregnancy, estrogen and progesterone, decrease once your baby is born. This signals to your body that it’s time to ramp up the milk supply. 

Prolactin is the hormone that increases your milk supply to make sure your newborn has adequate nutrition for growth. During each feeding, moms’ bodies release prolactin. It gradually increases available breast milk as your baby’s appetite grows. New moms should breastfeed or pump soon after delivery and then express milk regularly so the prolactin continually increases milk supply.

Oxytocin and Breastfeeding

Commonly known as the love hormone, oxytocin does much more than encourage bonding between you and your little one. Oxytocin is the hormone that prompts your milk to leave the alveoli and travel through the milk ducts to your baby’s mouth in a process called letdown. There are many physical clues that can tell moms’ bodies that their baby is ready to eat. 

When you first start breastfeeding, the suckling at your breast triggers your brain to release oxytocin and let down your milk. It can be difficult to prompt letdown, but there are a few tips and tricks to get oxytocin flowing. 

For starters, relaxing can encourage letdown, though we know that’s easier said than done. Take some deep breaths, place a warm compress on your chest, or massage your breasts before feeding to make letdown easier. As time goes on, letdown can occur more easily and sometimes unexpectedly. Although breastfeeding may be more of a scientific process than a mystical superpower, breastfeeding moms are still superheroes to us.


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