It is understandable why many pregnant individuals wonder about using a breast pump, especially if they are preparing for a new baby or currently nursing an older child. Pumping can seem like a practical way to prepare for the baby’s arrival or maintain an existing milk supply. However, this practice involves direct physiological effects that require careful consideration and guidance from a healthcare provider. The safety of using a pump depends entirely on the individual’s pregnancy risk profile and the gestational timing.
Safety and Medical Consensus
For the majority of low-risk pregnancies, medical consensus discourages breast pumping until the final weeks of gestation. This is because intense nipple stimulation carries a risk of triggering premature labor. The uterus can be stimulated to contract in response to hormonal signals released during pumping.
Some healthcare providers may permit or even recommend pumping or expression for specific purposes, but only after a woman reaches at least 36 to 37 weeks of pregnancy. Before this point, the potential for initiating labor is too high to justify the practice without a compelling medical reason.
The Physiological Risk Uterine Contractions
The primary risk of pumping involves the release of oxytocin. This hormone signals the milk ejection reflex, or “let-down.” When the nipple is stimulated by nursing or pumping, a signal is sent to the brain to release oxytocin into the bloodstream.
Oxytocin is also responsible for causing uterine contractions that initiate and maintain labor. For most of the pregnancy, the uterus is protected against oxytocin’s effects. This protection is maintained by low levels of oxytocin receptors and the presence of progesterone, which keeps the uterus relaxed.
As a woman approaches full term, the number of oxytocin receptors in the uterus increases dramatically, making the muscle far more sensitive. Pumping releases a surge of oxytocin, which, in a sensitive uterus, may lead to contractions strong enough to cause cervical change and potentially start labor.
Colostrum Harvesting A Specific Use Case
One common reason a pregnant individual might be advised to express milk is for colostrum harvesting. Colostrum, the nutrient-dense first milk, contains high levels of antibodies and easily digestible nutrients. Collecting and storing this milk before birth ensures the baby has immediate access, especially if early feeding difficulties are anticipated.
This practice is recommended for women with known risk factors, such as gestational diabetes, pre-existing diabetes, or a planned cesarean section that might delay the baby’s first latch. It is also beneficial if the baby has a condition like a cleft lip or a cardiac issue that could make initial feeding challenging. Expression must be initiated only after 36 or 37 weeks of pregnancy and with the direct approval of a midwife or doctor.
Manual Expression Preference
For this purpose, manual expression is often preferred over using a breast pump. Colostrum is thick and produced in tiny, concentrated amounts, making it difficult for a mechanical pump to collect efficiently. Hand expression allows for precise collection into a sterile syringe and provides a gentler form of stimulation. A healthcare provider will advise starting with short sessions, such as five to ten minutes once or twice a day, gradually increasing the frequency.
When Pumping is Strictly Contraindicated
In certain high-risk pregnancies, any form of nipple stimulation, including pumping, is forbidden due to the elevated risk of preterm labor. These conditions make the uterus too sensitive to oxytocin. Individuals with a history of preterm labor or who have previously had a baby born before 37 weeks should never attempt pumping.
Other conditions that strictly contraindicate pumping include:
- Carrying multiples (twins or triplets), which increases the risk of early delivery.
- Placenta previa, where the placenta partially or fully covers the cervix.
- Vasa previa, where fetal blood vessels cross the cervical opening.
- An incompetent cervix or a cervical cerclage (stitch) placed to prevent premature dilation.