Lactation and Colostrum: Milk and Newborn Immunity
Biology · Human Reproduction · NEET
Lactation is milk production by the mammary glands, which start making milk near the end of pregnancy. The very first milk, secreted in the initial few days, is called colostrum. Colostrum is a yellowish fluid rich in antibodies, mainly Immunoglobulin A (IgA), which give the newborn passive immunity. Memory hook: "First milk = Colostrum = Free IgA shield for baby."
Flow of lactation: mammary glands make milk late in pregnancy, the first milk (colostrum) carries IgA antibodies, which give the newborn passive immunity. Prolactin makes milk; oxytocin ejects it.
Your doubts, answered
Which antibody is present in colostrum?
Colostrum mainly contains Immunoglobulin A (IgA). NCERT says colostrum has 'several antibodies absolutely essential to develop resistance for the new-born babies'. In NEET, when the option list has IgA plus cells (macrophages, monocytes, NK cells), pick IgA, because an antibody is a protein, not a cell.
Is colostrum active immunity or passive immunity?
It is passive immunity. The baby does not make these antibodies itself; it receives ready-made antibodies (IgA) from the mother's colostrum. Received antibodies = passive immunity. This is important for NEET because the same concept links Human Reproduction to the Immunity chapter.
What is the difference between colostrum and normal breast milk?
Colostrum is the milk of the first few days of lactation. It is yellowish, thicker, and very rich in antibodies (especially IgA). Normal mature milk comes later and has more fat, lactose and water for growth. So colostrum = protection first, mature milk = nutrition and growth.
Which hormone controls milk ejection (let-down) and which controls milk production?
Two hormones, do not mix them up. Prolactin drives milk production (synthesis) in the alveoli. Oxytocin drives the milk ejection reflex (let-down), squeezing milk out. NEET loves this trap: oxytocin also causes the foetal ejection reflex during parturition, so the SAME hormone (oxytocin) does both milk ejection and foetal ejection.
When does lactation actually start?
The mammary glands differentiate during pregnancy and start producing milk towards the END of pregnancy, by the process called lactation. So milk-making begins before delivery, not after. Colostrum then flows in the first few days after the baby is born.
⚠️ The NEET trap ✗ Colostrum gives immunity because it contains defence cells like macrophages, monocytes or natural killer cells. ✓ Colostrum gives immunity because it contains antibodies, mainly Immunoglobulin A (IgA). Macrophages, monocytes and NK cells are cells, not antibodies. NCERT specifically says colostrum contains 'antibodies', so the antibody option (IgA) is correct. 🧠 Trap logic: 3 options are CELLS, 1 option is an ANTIBODY. NCERT said 'antibodies' -> choose the antibody = IgA.
Real NEET questions
2019
Colostrum, the yellowish fluid secreted by mother during the initial days of lactation, is very essential to impart immunity to the newborn infants because it contains:
A · Natural killer cells
B · Monocytes
C · Macrophages
D · Immunoglobulin A ✓
Solution: NCERT states colostrum contains several antibodies essential for resistance in the newborn. The antibody responsible for this passive immunity is Immunoglobulin A (IgA). The other three options are cells, not antibodies, so they are rejected.
2024
Assertion A: Breast-feeding during initial period of infant growth is recommended by doctors for bringing a healthy baby. Reason R: Colostrum contains several antibodies absolutely essential to develop resistance for the new-born baby. Choose the most appropriate answer.
A · Both A and R are correct, but R is NOT the correct explanation of A.
B · A is correct but R is not correct.
C · A is not correct but R is correct.
D · Both A and R are correct, and R is the correct explanation of A. ✓
Solution: Both statements are directly from NCERT. Doctors recommend breast-feeding early, and the reason is exactly that colostrum carries antibodies that build the newborn's resistance. So R correctly explains A.
2019
Which of the following hormones is responsible for both the milk ejection reflex and the foetal ejection reflex?
A · Estrogen
B · Prolactin
C · Oxytocin ✓
D · Relaxin
Solution: Oxytocin from the maternal pituitary causes strong uterine contractions (foetal ejection reflex) during parturition, and it also triggers the milk ejection (let-down) reflex during lactation. One hormone, two ejection reflexes.
Solved Human Reproduction NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Colostrum is yellowish because it is rich in proteins, antibodies (IgA) and other factors, and contains beta-carotene. For NEET, remember the exam word: 'yellowish fluid = colostrum'.
Does colostrum provide long-lasting immunity?
No. It provides passive immunity, which is fast but short-lived, because the baby only borrows the mother's antibodies. The baby's own (active) immunity develops slowly on its own later.
Which cells of the mammary gland make milk?
The alveoli. Each breast has 15-20 mammary lobes with clusters of cells called alveoli, and these alveolar cells secrete milk, which is stored in their lumens.
Is lactation part of the Human Reproduction chapter for NEET?
Yes. Lactation and colostrum come under section 2.7 'Parturition and Lactation' of the Human Reproduction chapter. It is a small but high-yield topic that repeats in NEET almost every few years.
