Background: Despite widespread cultural vilification, lactation–pregnancy overlap remains common. Its actual adverse effects remain uncertain.

Purpose: This study compared rates of success in reaching full-term delivery and newborn birth weights between two groups of multiparous pregnant women: those who breastfed during pregnancy and those who did not.
Methods: This was a comparative study conducted over 9 months, which examined two groups of women in the maternity units of two hospitals in Birjand, Iran. The first group comprised 80 women who breastfed for 30 days or more during pregnancy; the second group comprised 240 women who did not. The two groups had similar distributions in terms of maternal age, parity, medical/midwifery problems, and nutritional changes during pregnancy. Two trained nurses used a self-developed questionnaire to collect data.
Results: Results found no significant difference in full-term or non-full-term births rates and mean newborn birth weight between the two groups. We further found no significant difference between full-term or non-full-term births and mean newborn birth weight for those who continued and discontinued breastfeeding during pregnancy in the overlap group.
Conclusions/Implications for Practice: Results suggest that breastfeeding during normal pregnancy does not increase the chance of untoward maternal and newborn outcomes. Nurses and midwives should give expectant mothers appropriate evidence-based guidance and focus attention on promoting proper nutritional intake based on lactation status during pregnancy.

A Comparative Study of Breastfeeding During Pregnancy: Impact on Maternal and Newborn OutcomesJournal of Nursing Research: March 2012 - Volume 20 - Issue 1 - p 74–80