Breastfeeding during Pregnancy and Tandem Nursing: Is it Safe?

Recent research examined by Hilary Flower, Ph.D, Florida, USA

Originally published Apr 11, 2016

Is it safe to breastfeed during pregnancy?

When I began researching my book, Adventures in Tandem Nursing: Breastfeeding During Pregnancy and Beyond, my highest priority was to address the question of safety. Many midwives, The Womanly Art of Breastfeeding, and other woman-friendly resources gave it the green light. After all, many women had been breastfeeding during pregnancy without a problem. Meanwhile obstetricians warned women, incorrectly, that research showed it would cause miscarriage and preterm labor. In fact, neither camp could point to direct research about this important safety question—there wasn’t any.

To provide the best available answer at the time, I rolled up my sleeves and read medical research on the hormone oxytocin, about its release being triggered by nipple stimulation and as a potential trigger for labor. What I found was highly encouraging. Less oxytocin is released during breastfeeding, and throughout pregnancy the uterus is rendered “deaf” to oxytocin. One study discovered that even a high dose of synthetic oxytocin (Pitocin) is unable to trigger labor until a woman is at term (Kimura et al 1996). Similarly, the folklore that sex would induce labor has been put to rest, even for women who are at term (Tan et al 2006).

I interviewed Professor Lesley Regan, who runs the recurrent miscarriage clinic at St Mary’s Hospital, London. She was taken aback that anyone would suggest a connection between miscarriage and breastfeeding and said there was no basis for encouraging pregnant women to wean, even if they experienced a threatened miscarriage. The picture I was getting was that if a pregnancy is healthy, breastfeeding will not take it off track. If a breastfeeding mother experiences preterm labor or miscarriage, she most likely would have done regardless of the breastfeeding. Indeed I interviewed mothers for my book who did experience bleeding or symptoms of preterm labor; while some weaned to be on the safe side, some did not and they went on to have healthy babies.

At the time my book went to press (2003), these anecdotal or indirect indicators were the best I could provide. It is gratifying now, over a decade later, to see that medical research has done a lot to tackle the important question of safety. Three separate clinical studies have now been done, and breastfeeding has been exonerated as a cause of miscarriage, low birth weight, and preterm births.

Recent research

One study (Madarshahian and Hassanabadi 2012), in Iran, looked at 80 women who overlapped pregnancy with breastfeeding and 240 who did not. The researchers focused on normal pregnancies (excluding those that were high risk from the outset) and found no differences in the incidence of problems during pregnancy, including infection, hypertension, and bleeding. Further, the mothers who breastfed during pregnancy were just as likely as their non-breastfeeding peers to have full-term deliveries, avoiding preterm labor. The researchers concluded:
“This study supports the position that breastfeeding during normal pregnancy is not associated with higher risks of untoward maternal and newborn outcomes. Overlap breastfeeding is a personal decision for mothers.”

Another clinical study (Ishii 2009), conducted in Japan, looked at 110 women who overlapped breastfeeding and pregnancy and compared them to 774 who did not. This study found that miscarriage occurred in 7.3% and 8.4% of the pregnancies respectively, a non-significant difference. The author concluded:
“Even if the mother is pregnant, breastfeeding should be continued until natural weaning occurs.”
And commented:
“The issue of breastfeeding during pregnancy is a problem that needs to be overcome. Through misunderstanding and prejudice, innumerable infants have been deprived of their mother’s milk.”

In Iraq, a case-control study (Aldabran 2013) was conducted for one year with 215 pregnant women who breastfed during pregnancy and 288 pregnant women who did not. The incidence of preterm deliveries and low birth weight babies was not statistically different between the two groups. Oddly, the incidence of miscarriage was significantly lower in the breastfeeding group. Their conclusion:
“Breastfeeding does not increase the risk of miscarriage or preterm births, neither does it affect neonatal birth weight.”

Most recently, there was a study (Ayrim 2014), in Turkey: 165 women with singleton pregnancies who were breastfeeding the previous child. Forty-five of the 165 pregnant women continued lactating, whereas 120 did not. It bears pointing out that the breastfeeding pregnant women gained less weight than the non-breastfeeding group, and exhibited a decreased level of hemoglobin during pregnancy. Nonetheless, between the two groups, there was no statistically significant difference in hyperemesis gravidarum, threatened miscarriage, preeclampsia, premature labor and birth, neonatal weight, or Apgar scores. They concluded:
“Breastfeeding during pregnancy is not harmful, and health professionals should not advise weaning if overlapping occurs and should observe mother, infant, and fetus closely for negative effects, and if a negative effect occurs they should take precautions.”

Eating for three

The findings in the Iraq and Turkey studies regarding birth weight speak to another big concern associated with continued breastfeeding during pregnancy: is it risky to try to “eat for three?” Could it harm the fetus to compete for nutrients with a nursling? Or deplete the mother?

There is reason to believe that women in affluent countries with access to a varied diet need not worry about harming themselves, their fetus, or their nursling. Monitoring for adequate pregnancy weight gain, a basic varied diet of sufficient calories, and sufficient fluid intake are sufficient in most cases to consider the mother “on track” for eating for three. In some cases, supplementation with zinc and iron may be required, but a commitment to a perfect diet or to a vast water intake is unwarranted.

Women who are malnourished or undernourished are at a disadvantage when trying to provide for a fetus or a nursling, much less both simultaneously. A short recovery interval between birth and a new pregnancy adds to the strain for these mothers. More research is needed to determine the effects of nutritional supplementation as well as socioeconomic factors for the mother in these situations.

The evidence is in and getting stronger each year, that breastfeeding during pregnancy does not pose risks to a well-nourished mother in a healthy pregnancy. Equally strong is evidence of the benefits, both physical and emotional, of long term nursing when both mother and child wish to do so. Accordingly, the American Academy of Family Physicians came out with a position statement in 2008 endorsing breastfeeding during a normal pregnancy and emphasizing that weaning before two years increases the likelihood of childhood illness (AAFP 2008).

The Italian Society of Perinatal Medicine and the Task Force on Breastfeeding, Ministry of Health, Italy, conducted a thorough literature review to “determine the medical compatibility of pregnancy and breastfeeding.” Published in 2014, their report is the most thorough compilation of relevant medical research to date. In their conclusion they state:
“It must be recognized that, as a whole, the potential negative consequences of breastfeeding during pregnancy on the health of the mother/embryo/fetus/nursed infant are not evidence based. … Even in less developed countries, the risks related to overlapping breastfeeding and pregnancy seem to be associated more with the lack of sufficient nutrition of both the mother and the older child, with abrupt weaning, and with short intervals between births than the overlapping itselfBased on current knowledge, there is no medical evidence to indicate that in the general population, women of reproductive age are at higher risk of miscarriage or preterm delivery if they continue to breastfeed while pregnant. It is also unlikely that significant intrauterine growth restriction may result from the pregnancy-breastfeeding overlap, particularly in healthy and well-nourished women from developed countries.”

It’s time to debunk the myth, and let women make individualized, personal decisions about breastfeeding during pregnancy as well as any other time. As always, choices during pregnancy and breastfeeding must be fine-tuned to the individual. As a mother goes along she should continue to ask herself, “Does this overlap feel harmonious within my body? Does it feel like this is working well?” As she considers these questions, she should not be burdened with the myth that she is doing something strange or dangerous. If you are considering breastfeeding during pregnancy, or advising a woman who is, it’s ideal to have an obstetrician or midwife who can consider the genuine medical research on safety, as well as the overwhelming research on the continued benefit of long term nursing to the older child.

Breastfeeding During Pregnancy and Tandem Nursing 

Albadran, Maysara, M. Effect of breastfeeding during pregnancy on the occurrence of miscarriage and preterm labour. Iraqi Journal of Medical Sciences 2013; 11.3.

American Academy of Family Physicians (AAFP). Position Statement on Breastfeeding. 2008.

Ayrim, A. et al. Breastfeeding throughout pregnancy in Turkish women. Breastfeeding Medicine 2014; 9(3): 157–160.

Ishii, H. Does breastfeeding induce spontaneous abortion? J Obset Gynaecol Res 2009; 35(5): 864–868.

Kimura, T. et al. Expression of oxytocin receptor in human pregnant myometrium. Endocrinology 1996; 137: 780–785.

Madarshahian, F. and Hassanabadi, M. A Comparative study of breastfeeding during pregnancy: Impact on maternal and newborn outcomesJ Nursing Research 2012; 20(1): 74–80.

Merchant, K. et al. Maternal and fetal responses to the stresses of lactation concurrent with pregnancy and of short recuperative intervals. Am J Clin Nutr 1990; 52:280–88.

Tan, P. et al. Effect of coitus at term on length of gestation, induction of labor, and mode of delivery. J Obstet and Gynaecol 2006; 108(1): 134–140.

Hilary Flower is the author of Adventures in Tandem Nursing: Breastfeeding During Pregnancy and Beyond, LLLI 2003, and Adventures in Gentle Discipline, LLLI 2005. She lives with her three children in Florida, USA.