The Safety of Breastfeeding During Pregnancy

by Hilary Dervin Flower, MA

Are you ready to try to conceive your second child, but still enjoying a breastfeeding relationship with your firstborn? Or perhaps you are breastfeeding your child over a kicking baby belly? If so you are not alone -- far from it.

In a study of 179 mothers who had breastfed for at least six months, 61% had also breastfed during a subsequent pregnancy.1 Of these, 38% went on to nurse both newborn and toddler postpartum, an arrangement known as "tandem nursing."

Moreover, continued breastfeeding can be helpful to your toddler's adjustment to a new baby. Besides, what better way to rest your tired pregnant body while caring for an active baby or toddler?

In contemplating the healthiness of an overlap you will want to consider how breastfeeding is fitting in with your needs for rest, adequate pregnancy weight gain, and your overall sense of well-being. You will do well to take into account that breastfeeding can be painful or agitating for many mothers for some or all of pregnancy, leading some mothers to push for weaning. The milk tends to dwindle by mid-pregnancy; some children self-wean in response, while others don't seem to care.

Another concern you may have is the fact that breastfeeding causes contractions. Could breastfeeding trigger preterm labor or miscarriage? I have dug deep in the scientific literature and interviewed over 200 mothers, seeking hard facts to help mothers make the most informed and balanced assessment they can of this important safety question. Indeed, this question was my top priority as I researched my new book Adventures in Tandem Nursing: Breastfeeding during Pregnancy and Beyond, published in July 2003 by La Leche League International. Here's what I learned.

Breastfeeding and Contractions

Nipple stimulation releases the hormone oxytocin into the bloodstream. Oxytocin is important for breastfeeding because it is the chemical messenger that tells breast tissue to contract and eject milk (the "milk ejection reflex"). Oxytocin also tells the uterine tissue to contract. All women experience uterine contractions during breastfeeding, although they are usually too mild to be noticed. Nipple stimulation can be used to ripen the cervix when a woman is at term, and can also augment labor after it is underway. Postpartum breastfeeding efficiently shrinks the uterus back to pre-pregnancy size.

Given these associations, it seems a short jump to guess that breastfeeding might trigger labor before its time. This question deserves medical study, and it is important to bear in mind that at this time there have been no controlled studies.

At the same time, preliminary data do suggest that breastfeeding and healthy term births are quite compatible. Sherrill Moscona's 1993 survey of 57 California mothers who breastfed during pregnancy concluded that breastfeeding resulted in no apparent adverse consequences to the mothers' pregnancies.2

There are also countless anecdotal reports of mothers who have breastfed throughout pregnancy and given birth to healthy term babies. Of course, some pregnancies are not destined to proceed as we hope, whether the mother is breastfeeding or not, and so breastfeeding mothers have suffered their share of preterm labor and miscarriage as well.

Most mothers notice no contractions during breastfeeding, even during pregnancy (93% in the Moscona survey).3 Interestingly, even those who experience intense "nursing contractions" often find that the contractions cease soon after ending the breastfeeding session.4 Like Braxton-Hicks contractions, nursing contractions commonly occur without disrupting the pregnancy. How might that work? The scientific literature has a lot to tell us about that.

A Primer on the Signs of Preterm Labor

Remember to contact your caregiver immediately if you experience any of these possible warning signs: