The first time you express a feed of colostrum and it produces five drops on the side of a syringe, it's hard not to feel like something has gone wrong. After nine months of growing a baby, that's it? It looks like nothing. The midwife smiles and says it's plenty. They're right.
A newborn's stomach at birth is the size of a cherry — it physically holds about 5–7 ml. Their kidneys can't yet manage large volumes of fluid. Five drops is not a poor effort; it's roughly the right portion size. And what's in those drops is unusual enough that no formula has fully replicated it.
Healthbooq covers breastfeeding from the first feed onwards.
What Colostrum Is
Colostrum is the milk your breasts produce from around 16 weeks of pregnancy through to the third or fourth day after birth, when it gradually transitions to mature milk. It's thick, often yellow or orange in colour, and looks more like a watery custard than the white milk most people expect.
The composition is striking when set next to mature milk:
- Higher protein — about three times the level of mature milk.
- Lower fat — only about a third the level.
- Lower lactose — easier on the gut while bilirubin levels rise and gut bacteria establish.
- Much higher concentrations of immune components — antibodies, white blood cells, antimicrobial proteins.
- Much higher growth factors that physically remodel the newborn gut.
It's not really a food in the calorie sense — it's a biological tool kit for the first 72 hours of extrauterine life.
What's in It That Matters
Secretory immunoglobulin A (sIgA). The dominant antibody of mucosal immunity. It coats the lining of the newborn gut and airways, physically blocking bacteria and viruses from attaching to or crossing the gut wall. Colostrum is especially rich in sIgA — concentrations several times higher than mature milk.
Lactoferrin. An iron-binding protein with broad antibacterial activity. It deprives pathogens of the iron they need to grow.
Lysozyme. An enzyme that breaks down bacterial cell walls.
Living white blood cells. Real, functional macrophages, lymphocytes, and neutrophils, drawn from the mother's circulation into the milk. The colostrum effectively transfers some of the mother's active immune system to the baby.
Growth factors — especially epidermal growth factor (EGF) and insulin-like growth factor (IGF). These stimulate the newborn's gut lining to mature rapidly. At birth, the gaps between intestinal cells are still wide enough to let large molecules and microbes through; colostrum closes those gaps within days. This "gut closure" reduces the risk of food allergy and the entry of bacteria into the bloodstream.
Beta-carotene. Gives colostrum its yellow-orange colour. Antioxidant.
Probiotic seeding. Colostrum contains the maternal milk microbiome that helps establish the newborn's own gut bacteria — the foundation of the immune system, digestive function, and even mood regulation in later life.
Why the Volume Is Small (and Why That's Right)
Colostrum is produced under the influence of prolactin, which rises through pregnancy. Progesterone, made by the placenta, holds back large-scale milk production until birth. When the placenta delivers, progesterone drops within hours, and the brake comes off; transitional milk starts to come in 2 to 5 days later.
Before that, colostrum is all there is, and the volumes match the baby's capacity:
- Day 1: typically 7–10 ml per feed (about 2 teaspoons), 30–60 ml in 24 hours total.
- Day 2: 15–20 ml per feed.
- Day 3: 30 ml or more per feed as transitional milk starts to come in.
Frequency matters far more than volume per feed. Aim for 8–12 feeds in 24 hours in the first days. Each feed both provides what the baby needs and signals demand to the breasts, which is what triggers the larger milk production to follow.
A small weight loss in the first days is normal — up to 7 per cent of birth weight is expected. Above 10 per cent, the team will reassess feeding. Most babies regain their birth weight by 10–14 days.
Why Frequent Feeding in the First 24–48 Hours Matters
Two things are happening in parallel:
- The baby is feeding. Tiny volumes of colostrum, often, settle a stomach the size of a cherry far better than larger volumes less often.
- The breasts are being told to make more milk. Each effective feed releases prolactin and oxytocin, signalling demand. Frequent feeding in the first 48 hours is the strongest predictor of a robust milk supply by day 5.
Skipping or stretching out feeds in the first day — including overnight — slows the transition and is a common cause of delayed milk coming in and early breastfeeding difficulty. If the baby is sleepy after birth (very common, especially after a long labour or with pain relief), wake them every 2 to 3 hours and offer the breast.
Antenatal Colostrum Harvesting
From around 36 weeks of pregnancy, women whose babies are at higher risk of needing extra feeds in the first 24 hours can hand-express and collect colostrum into 1 ml syringes, freeze it, and bring it to hospital. If the baby then needs a top-up, the mother's own colostrum is used rather than formula.
NICE and the Unicef Baby Friendly Initiative recommend offering antenatal harvesting for:
- Diabetes in pregnancy on insulin — the most common indication. Babies of insulin-treated mothers have higher fetal insulin levels in utero and are at significant risk of neonatal hypoglycaemia in the first hours.
- Expected preterm birth.
- Expected small-for-gestational-age baby.
- Known cleft lip or palate — feeding may be more difficult initially.
- Known Down syndrome or other conditions that may affect early feeding.
- Multiple pregnancy.
The midwife or a feeding specialist will demonstrate the technique. A typical session yields a few drops to a few millilitres. Sessions of 5–10 minutes per breast, two to three times a day, build up a useful supply over the last few weeks of pregnancy.
Don't start before 36 to 37 weeks. Nipple stimulation can trigger uterine contractions; the evidence that this actually causes preterm labour is limited, but the cautious advice is to wait until term-ish to be safe.
Transition to Mature Milk
The change from colostrum to mature milk is gradual:
- Days 3–5: "milk coming in." Breasts noticeably fuller, sometimes uncomfortably so. Volumes per feed climb. The milk lightens in colour and thins in consistency.
- Days 5–14: transitional milk. Fat and lactose rising; immune component concentrations falling but still substantial.
- Around 2 weeks: mature milk established, though composition continues to change subtly across feeds and through the months of breastfeeding.
Mature milk still contains sIgA, lactoferrin, and live cells — at lower concentrations than colostrum but in much larger total volumes. The immune protection of breast milk continues throughout breastfeeding.
When Things Don't Go to Plan
Most mothers can produce colostrum normally. A few situations can make it more difficult:
- Significant blood loss at delivery — can delay milk coming in by a day or two.
- Caesarean birth — slightly delayed transition on average, but normalises with frequent feeding.
- Polycystic ovary syndrome, prior breast surgery, hypoplastic breasts — may reduce colostrum and milk volumes; specialist breastfeeding support is helpful.
- High maternal body mass index — modest delays sometimes seen.
- Stress and pain — can inhibit oxytocin, the let-down hormone. Skin-to-skin and a calm environment help.
If your baby is feeding poorly, weight loss is more than 10 per cent, or you're worried about colostrum supply, ask the midwife or health visitor for a feeding assessment. A breastfeeding specialist can usually identify the issue and adjust technique. The Association of Breastfeeding Mothers (abm.me.uk) and La Leche League GB (laleche.org.uk) both run helplines and local support groups.
Key Takeaways
Colostrum is the thick yellow-orange first milk produced from about 16 weeks of pregnancy through the first 2–4 days after birth. The volumes are small — about 7–10 ml per feed on day 1 — and that's exactly what a newborn's marble-sized stomach can hold. What it lacks in volume it makes up in concentration: it's packed with antibodies (especially secretory IgA), white blood cells, and growth factors that seal the gut and protect against infection. Antenatal colostrum harvesting from 36 weeks is offered to women whose babies are at higher risk of low blood sugar after birth — including those with diabetes, expected preterm, or a known cleft.
