Antenatal expression, also known as colostrum harvesting, is the practice of gently hand-expressing milk in the weeks leading up to delivery. The first milk produced is colostrum, a concentrated substance that can be stored and given to the newborn later if needed. Many parents consider this practice around 38 weeks of pregnancy, which is considered full-term. Because nipple stimulation can affect the uterus, it is reasonable to question the safety of starting at this stage. This article explores the medical consensus on when antenatal expression is safe and provides details on how to collect and store this first milk.
When Is Antenatal Expression Safe
The core safety concern with antenatal expression is the potential for nipple stimulation to trigger labor. Nipple stimulation causes the pituitary gland to release oxytocin, the hormone responsible for uterine contractions during labor. While the amount of oxytocin released during gentle expression is usually not enough to start labor in an uncomplicated pregnancy, it can cause the uterus to contract.
For low-risk pregnancies, medical professionals generally advise starting antenatal expression between 36 and 37 weeks of gestation. Beginning at 38 weeks is well within the recommended timeframe for a full-term pregnancy. Once a pregnancy is considered full-term, the risk associated with minor uterine activity is significantly reduced.
You may notice mild, painless uterine tightening, known as Braxton Hicks contractions, during or after a session. Healthcare providers instruct patients to stop expressing immediately if contractions become painful, regular, or feel like true labor. Always obtain clearance from your doctor or midwife before beginning to confirm that your pregnancy status is low-risk and safe for this practice.
Harvesting Colostrum Before Delivery
Antenatal expression builds a reserve of colostrum, which is the newborn’s ideal first food. Colostrum is uniquely concentrated, delivering high levels of protective antibodies and growth factors that prime the baby’s developing gut. It is lower in fat and higher in protein than mature milk, making it easy for a newborn’s digestive system to process.
Colostrum helps stabilize a newborn’s blood sugar levels and assists the baby in passing meconium, which reduces the risk of jaundice. Having a supply of expressed colostrum is especially beneficial for babies at an elevated risk of neonatal hypoglycemia, such as those born to mothers with gestational or pre-existing diabetes.
Storing colostrum in advance provides a buffer if the baby has difficulty with their initial latch or if the parent and baby are separated. This separation might occur due to a planned Cesarean section or a required stay in the neonatal unit. In these scenarios, pre-harvested colostrum ensures the baby receives human milk instead of formula top-ups, supporting exclusive breastfeeding.
Proper Technique and Storage Methods
The recommended method for collecting colostrum antenatally is hand expression, not a breast pump. Colostrum is thick and produced in very small volumes—often just a few drops—which tends to cling to pump parts, leading to waste. Hand expression allows you to directly collect the droplets into a suitable container with greater precision.
To begin, gently massage your breast. Place your thumb and forefinger in a “C” shape about an inch behind the nipple and areola. Press inward toward the chest wall, then compress the fingers together to express the colostrum, repeating this rhythmically. Start slowly, expressing for only 5 to 10 minutes per breast, one to two times a day, to avoid overstimulation.
The expressed colostrum should be collected directly into sterile, small-volume containers, such as 1 milliliter or 2 milliliter syringes, which a healthcare provider can often supply. Label each syringe with the exact date and time of the first expression. You can store the syringe in the refrigerator between sessions for up to 24 hours, adding more colostrum to the same syringe before capping it and moving it to the freezer. Frozen colostrum can be safely stored for up to six months at -18°C or lower.
Medical Conditions That Prohibit Pumping
While antenatal expression is safe for most low-risk pregnancies, certain medical conditions make the practice inadvisable due to the risk of inducing premature labor. Any condition that predisposes a pregnancy to early delivery makes the oxytocin-releasing effect of nipple stimulation too risky. You must not begin expressing if you have a history of threatened or actual preterm labor in this or a previous pregnancy.
Conditions affecting the placenta or cervix also prohibit the practice. These include:
- Placenta previa, where the placenta covers the cervix.
- A cervical stitch (cerclage) or a history of cervical incompetence.
- Any unexplained vaginal bleeding during the pregnancy.
- Carrying multiples, such as twins or triplets, or having a complex medical history.
If any of these conditions apply, you must receive explicit, individualized clearance from your obstetrician before attempting colostrum harvesting.