For most healthy pregnancies, breastfeeding is safe to continue. The oxytocin released during nursing does cause mild uterine contractions, but in a low-risk pregnancy, these are not strong enough to trigger preterm labor. Many women around the world breastfeed throughout pregnancy and go on to deliver healthy, full-term babies.
That said, there are specific situations where it’s not recommended, and the experience of nursing while pregnant comes with real physical changes worth preparing for.
Why It’s Generally Considered Safe
The main concern people have is that breastfeeding stimulates oxytocin, the same hormone involved in labor contractions. While this is true, the uterus in early and mid-pregnancy has far fewer oxytocin receptors than it does at full term. The small, rhythmic contractions caused by nursing (similar to Braxton Hicks contractions) are not sufficient to initiate labor in a pregnancy that is otherwise progressing normally.
A 2012 study by Madarshahian and Hassanabadi compared pregnant women who breastfed an older child with those who did not. There was no significant difference in full-term delivery rates between the two groups, and birth weight was also unaffected. This is one of the clearest pieces of evidence that the fetus is not being shortchanged by continued breastfeeding.
When You Should Stop
Breastfeeding during pregnancy is not recommended if you are at risk for preterm labor. Because nursing can stimulate uterine contractions, it may increase the chance of premature birth in women who are already vulnerable. Your provider may advise you to wean if you have:
- A history of preterm labor or premature birth
- Cervical insufficiency (a cervix that shortens or opens too early)
- A multiple pregnancy (twins, triplets)
- Unexplained vaginal bleeding
- A current high-risk pregnancy for other reasons
There are also general contraindications to breastfeeding unrelated to pregnancy. These include untreated HIV without viral suppression, HTLV-1 or HTLV-2 infection, active use of certain illicit drugs, and a few other specific conditions. These apply whether or not you’re pregnant.
Your Milk Supply Will Change
One of the most noticeable shifts happens around the fourth or fifth month of pregnancy, sometimes earlier. Most women see a significant drop in milk supply. This is driven by the hormonal changes of pregnancy, and unlike a typical supply dip, nursing more frequently or pumping won’t reverse it. Your body is essentially prioritizing the pregnancy.
The composition of your milk also changes. Sometime between 16 and 22 weeks of pregnancy, your body begins producing colostrum, the thick, concentrated early milk meant for newborns. It’s rich in protein, white blood cells, and protective nutrients. Your nursing toddler may notice the taste difference. Some children self-wean during this period because of the change in flavor or reduced volume, while others continue nursing without complaint.
An important reassurance: your older child’s nursing will not use up the colostrum your newborn needs. No matter how often or how long the older child breastfeeds, colostrum will still be available after birth for the new baby.
Nipple Soreness and Physical Discomfort
Pregnancy hormones make nipples significantly more sensitive, and many women find that breastfeeding becomes uncomfortable or even painful in ways it wasn’t before. This is one of the most common reasons women choose to wean during pregnancy, even when they’d planned to continue.
If you want to push through the discomfort, a few strategies can help. Check your older child’s latch: if your nipple looks pinched or flattened after a feeding, the latch may need adjusting. Avoid harsh soaps or astringent products on your nipples. Washing with plain water is enough. Shorter nursing sessions, or setting gentle limits on how often your toddler nurses, can also reduce the cumulative irritation. Some women find that the sensitivity peaks in the first trimester and becomes more manageable later, though this varies widely.
Eating Enough for Both
Pregnancy alone requires roughly 300 extra calories per day during the second and third trimesters. Breastfeeding adds another estimated 500 calories above your pre-pregnancy intake. If you’re doing both simultaneously, the caloric demand is real and can sneak up on you, especially if nausea is suppressing your appetite in the first trimester.
The practical advice is to eat to your hunger rather than trying to hit an exact number. Focus on nutrient-dense meals, stay well hydrated, and pay attention to signs that you’re running low: unusual fatigue, dizziness, or feeling constantly depleted beyond normal pregnancy tiredness. A prenatal vitamin continues to be important, but it’s a supplement to food, not a replacement for adequate calories.
Planning for Tandem Nursing
If you breastfeed through your entire pregnancy, you’ll arrive at tandem nursing: feeding both a newborn and an older child. This works well for many families, and it comes with some unexpected benefits. Your older child’s nursing can ease engorgement once your mature milk comes in, and if your newborn has trouble latching in the early days, your toddler’s continued nursing helps protect your milk supply.
The main practical concern is making sure the newborn gets enough. Some mothers handle this by always offering the breast to the newborn first, or by gently limiting the older child’s sessions during the first few weeks. With each pregnancy, your body tends to produce more milk, so oversupply can actually be more of an issue than undersupply. If your letdown is too fast for the newborn, letting the older child nurse first or expressing a small amount before latching the baby can help slow the flow.
Tandem nursing can also ease the emotional transition for the older sibling. It maintains a familiar source of comfort during a time when everything else in their world is shifting. That said, it’s physically demanding, and plenty of mothers decide to wean the older child before or after the birth. There’s no single right approach.