Which Month Does Breast Milk Start During Pregnancy?

When does breast milk start during pregnancy?

Your breasts begin preparing for milk production in the first trimester, as early as week 6 to 8. The first milk, called colostrum, starts forming around week 16 to 22 of pregnancy. Some women notice small amounts leaking from week 14 onwards, while others see nothing until after delivery. Mature breast milk does not come in until 2 to 5 days after birth, once progesterone levels drop sharply following delivery of the placenta.

What Is Colostrum and Why Does It Matter?

Colostrum defined: Colostrum is the first form of breast milk, produced by the mammary glands during late pregnancy and in the first few days after birth. It is thick, sticky, and typically yellow or golden in colour. Colostrum is extremely concentrated, high in protein and antibodies (especially secretory IgA), and low in fat and lactose compared to mature milk.

Colostrum is often called “liquid gold” in clinical breastfeeding literature, not for dramatic effect, but because of its composition. A few millilitres per feed is sufficient for a newborn’s stomach in the first day or two. According to the World Health Organization (WHO), colostrum provides newborns with essential passive immunity against infections, and its laxative properties help the baby pass meconium (first stool), reducing the risk of neonatal jaundice.

Month-by-Month: How Your Breasts Change During Pregnancy

Month 1 to 2 (Weeks 1 to 8): First Structural Changes

The first signs of breast change typically appear before a missed period is even confirmed.

From weeks 6 to 8, the breasts begin to feel tender, swollen, or heavier. The nipple and areola area may darken. The veins under the skin of the breast may become more visible as blood supply increases.

Inside the breast, the milk ducts begin to grow and branch. The milk-producing glands (alveoli) start multiplying. These changes are driven by rising oestrogen and progesterone and are happening at a structural level long before any milk is formed.

No colostrum is present yet, and no leaking occurs at this stage. The sensitivity and swelling are the predominant changes.

Month 2 to 3 (Weeks 9 to 12): Breast Growth Continues

The breasts continue to enlarge. The areola (the darker skin around the nipple) continues to widen and deepen in pigmentation. Small raised bumps called Montgomery’s tubercles appear on the areola. These are modified sebaceous glands that produce oil to keep the nipple and areola lubricated and protected, and they increase in number during pregnancy.

The milk duct network continues to expand throughout the breast tissue. No colostrum is detectable yet in most women.

Month 3 to 4 (Weeks 13 to 16): Colostrum Begins Forming

Around weeks 14 to 16, the body begins producing colostrum. The milk-producing cells (lactocytes) in the alveoli start secreting this first milk into the ducts.

Some women notice a yellowish or clear discharge from the nipple at this point, particularly after a warm shower, during breast examination, or during sexual activity. Others notice nothing at all. Both are normal. The progesterone present in pregnancy prevents most of this colostrum from flowing out of the nipple.

Month 4 to 5 (Weeks 17 to 22): Colostrum Is Present

This is the stage at which colostrum is present in the breasts of most pregnant women. By week 22, the majority of women who are going to notice colostrum leaking will have done so.

The breasts may feel fuller. Some women notice small yellow or orange stains on their bra or nightwear. Others can express a small amount of colostrum if they gently squeeze the areola.

A clinical note from the ACOG (American College of Obstetricians and Gynecologists): the absence of any visible colostrum during pregnancy does not predict breastfeeding ability or colostrum production after birth. The absence of leaking is not a concern.

Month 5 to 7 (Weeks 23 to 32): Colostrum Increases

Colostrum production continues and typically increases in volume during the second half of pregnancy. The breasts grow larger as more milk-producing tissue develops.

Leaking may increase, particularly with warm temperatures or physical stimulation. Nursing pads can be used if leaking is significant. Expressing colostrum during pregnancy is generally not recommended unless a midwife or doctor has specifically advised it for a clinical reason (for example, collecting antenatal colostrum for a baby with a known feeding challenge at birth).

Month 8 to 9 (Weeks 33 to 40): Ready for Birth

By the third trimester, the mammary glands are fully developed and ready to provide colostrum immediately after birth. The colostrum present is nutritionally complete for a newborn.

The breasts may feel heavy, warm, and full. Leaking may be more frequent. This is normal and does not indicate that you will run out of colostrum before delivery.

After Delivery: What Happens to Breast Milk

Understanding what happens after birth helps mothers prepare for the first week of breastfeeding.

The moment the placenta is delivered, progesterone levels fall. Over the next 24 to 72 hours, prolactin takes over and triggers the “milk coming in.” The transition from colostrum to mature milk is marked by breast engorgement: the breasts become noticeably fuller, harder, and sometimes uncomfortable.

Frequent feeding in the first days, regardless of how little colostrum seems to be available, is the most effective way to establish milk supply. Each feed signals the breast to produce more.

Why Milk Does Not Come In During Pregnancy?

This is one of the most common points of confusion: if the breasts are already producing colostrum from week 16 or so, why doesn’t milk “come in” during pregnancy?

The answer is progesterone.

During pregnancy, progesterone levels are very high. Progesterone actively suppresses the full release of milk from the breast tissue, even though the mammary glands are producing colostrum. The hormone prolactin, which drives milk production, rises throughout pregnancy but is blocked from acting on the milk-producing cells by progesterone.

When the placenta is delivered after birth, progesterone drops sharply and dramatically. This progesterone withdrawal signals the prolactin to take over, and the breasts transition from colostrum to transitional milk and then to mature milk over the following days.

This is why:

• Colostrum may be present during pregnancy, but it does not flow freely
• Full milk “coming in” always happens after delivery, not before
• A woman who is pregnant and breastfeeding a toddler simultaneously (called tandem nursing) may notice her milk changes to colostrum again around weeks 16 to 20 of pregnancy

How to Prepare for Breastfeeding During Pregnancy?

The best preparation for breastfeeding is informational, not physical.

• Learn how breastfeeding works before the baby arrives: latch technique, feeding frequency (8 to 12 times per 24 hours in the newborn period), what normal infant weight loss looks like
• Attend a breastfeeding class or speak with a lactation consultant before delivery
• Discuss your breastfeeding intentions with your obstetrician and the paediatric team who will care for your baby
• Plan for skin-to-skin contact immediately after birth: this activates the newborn’s feeding instinct and the maternal oxytocin response simultaneously
• There is no evidence that nipple exercises, creams, or manual preparation of the nipple during pregnancy improves breastfeeding outcomes. The body does the preparation on its own

Expert Guidance at Mamata Fertility Hospital, Hyderabad

At Mamata Fertility Hospital in Secunderabad, Hyderabad, the maternity care team provides comprehensive antenatal guidance from early pregnancy through to delivery and postpartum care. Breastfeeding preparation, including advice on colostrum, milk supply, and postnatal lactation support, is part of the standard antenatal care provided to all patients.

Dr. Aarti Deenadayal Tolani and the team offer:

• Antenatal consultations covering pregnancy month by month
• High-risk pregnancy monitoring and care
• Postnatal lactation support
• Guidance for women who have conceived through IVF or other fertility treatments

Phone: +91 8790337035 | 040 45678899
Address: Secunderabad, Hyderabad, Telangana
Hours: Monday to Saturday, 8:00 AM to 6:00 PM

FAQs

Breastfeeding After Fertility Treatment: What to Expect?

Women who conceive through IVF or other assisted reproductive treatments can breastfeed in exactly the same way as women who conceive naturally. The hormonal changes of pregnancy prepare the mammary glands for milk production regardless of how conception occurred.

If you have had a multiple pregnancy (twins or more, which is more common following fertility treatment), breastfeeding is still possible. Many mothers successfully breastfeed twins simultaneously. Speak with your specialist at Mamata Fertility Hospital about your feeding plans if you are expecting a multiple birth.