J Obstet Gynaecol Res. 2009 Oct;35(5):864-8.
Aim: To verify the hypothesis that even if breastfeeding is continued during pregnancy, there are no harmful effects on pregnancy.
Methods: The outcomes of pregnancies in mothers who continued breastfeeding during pregnancy were studied. One hundred and ten pregnant women were recruited who had one full-term baby, no experience of premature birth or abortion, and who continued to breastfeed at diagnosis of pregnancy. Age and pregnancy history matched 774 pregnant women were selected as a control group. All of the control women stopped breastfeeding at least 3 months before becoming pregnant. We reviewed the outcome of each pregnancy retrospectively from patient records. Statistical analysis was conducted using the chi(2) test.
Results: Eight of 110 pregnancies (7.3%) resulted in spontaneous abortion in the breastfeeding group, and 65 of 774 pregnancies (8.4%) in the control group. There were no statistically significant differences between the two groups (P > 0.05).
Conclusion: Even if the mother is pregnant, breastfeeding should be continued until natural weaning occurs. Further study is required to conclude safety of breastfeeding and premature birth.