Dear Doctor Ragab, Your question about nursing and pregnancy has me a little confused. You talk about "a pregnant lady nursing her newborn." I am confused because to me a "newborn" is a baby under one month old, and it would be very unusual for someone to become pregnant that soon after giving birth, especially if she is breastfeeding. So I will assume that you are talking about a lady who becomes pregnant while she is nursing a baby, even perhaps quite a young baby, but probably a baby over 1 month old. 1. Does the milk composition change when a nursing mother gets pregnant? Many women report a decrease in milk volume. Moscone and Moore surveyed 51 American women who continued to breastfeed after becoming pregnant; the mean age of their nursing child when they became pregnant was 18.5 months, with a range of 4-42 months. 70% reported they had less milk; 30% noticed no difference. Neville and Neifert quote anecdotal reports from mothers, saying that volume declines and the milk is more colostrum-like in nature. Nursing babies who are old enough to talk about the milk have told their mothers that the volume, ease of flow, and taste are different. The main concern would be for a baby under 6 months old who is still dependent on the breast for all his nutrition. If the volume decreases significantly, he might need supplementation in order to meet his nutritional needs. 2. Does the mother have to stop nursing? Why or when? In many cultures around the world people believe that breastfeeding during pregnancy is harmful, so women may be told that they must wean during pregnancy. However, many other cultures do not prohibit nursing during pregnancy. I understand that there is a great deal of anecdotal evidence showing that there is no harm to the mother or to either child when breastfeeding continues through pregnancy. La Leche League in The Breastfeeding Answer Book advises that a well-nourished mother should be able to provide enough nutrients for herself and both children. She might have to eat extra food and perhaps take vitamin or mineral supplements. Some people voice concern about the uterine contractions triggered by nipple stimulation. However, uterine contractions are normal during pregnancy, and there is no documentation that they have a harmful effect on the fetus or on the pregnancy. One "rule of thumb" is that if it is safe for the woman to have sexual intercourse (which also triggers contractions), it's safe for her to breastfeed. Moscone and Moore found that 39% of their subjects reported breast and/or nipple pain; 34% reported fatigue; 22% reported increased irritability; 5% reported uterine contractions. Newton and Theotokatos, studying 503 women, found that 74% reported breast and/or nipple pain and 57% reported increased irritability. La Leche League gives three medical reasons a mother might need to consider weaning: uterine pain or bleeding; history of premature delivery; continued weight loss by mother. So I think your answer is: the healthy pregnant mother does not have to stop nursing. She may discover that she does stop nursing, either because the baby loses interest in a smaller milk supply, or milk with a new taste, or because the mother is uncomfortable or easily annoyed by breastfeeding. 3. Is there any deleterious effect on the fetus of a nursing mother? La Leche League refers to a study by Merchant of 253 women which compared the birth weights of a group of babies whose mothers weaned the older sibling before they conceived with the birth weights of a group of babies whose mothers breastfed into the 2nd or 3rd trimester. This study found no difference in the birth weights but did note that the nursing mothers took more nutritional supplements and had less maternal fat stores. 4. Is there any deleterious effect on the nursing baby? Only if he is still young enough to be primarily dependent on mother's milk, so that a decline in supply is a problem. The hormones of pregnancy that appear in the milk do not harm the nursing child. Some questions you didn't ask: 5. Why would a woman want to breastfeed when she is pregnant? The mother sees that the baby still enjoys breastfeeding, still needs the milk or the comfort he gets from the breast. She may also still enjoy being able to comfort him, or she may continue to breastfeed because it is important to the child, even if it is painful or annoying for her. 6. What if the older child still nurses when the baby is born? This is not a problem. She will make milk for both children, by the supply and demand system. Merchant K et al (1990) Materal and fetal responses to the stresses of lactation concurrent with pregnancy and of short recuperative intervals. AmJClinNutr 52:280-88. Mohrbacher N & J Stock (1997) Breastfeeding Answer Book, Revised Edition. La Leche League International. (This, in my opinion, is the best reference!) Moscone SR & MJ Moore (1993) Breastfeeding during pregnancy. J Hum Lactation 9(2), 83-88. Neville MC & MR Neifert (1983) Lactation: physiology, nutrition and breast- feeding. Plenum Press. Newton N & M Theotokatos (1973) Breastfeeding during pregnancy in 503 women: does a psychobiological weaning mechansim exist in humans? Emotion and reproduction 20B:845-849. I hope that this answers your questions. Peace and best wishes. Chris Mulford