|Food and Nutrition Bulletin Volume 17, Number 4, 1996 (UNU, 1996, 163 pages)|
|Impact on fertility|
Could you comment on what may be one of the larger effects of breastfeeding on maternal health and well-being, that is, avoiding two pregnancies back-to-back and two children under one year of age?
That is covered in my considerations of the health of the subsequent child.
I understand that there is a protein in human milk that induces programmed cell death in many malignant cell lines. Could it be that in a mother who has been lactating several times, there would be such milk proteins remaining in the gland, which could induce apoptosis of cells that in time might turn into cancers?
An attractive hypothesis, but I don't know enough about it to answer your question. Does anyone else want to take it on?
No, I wouldn't like to take it on. I was going to ask a different question. One of the features of prolonged lactation is the reduction of the number of reproductive cycles that a woman has in her life. As I understand it, most circumstances that produce such a reduction also produce a reduction in ovarian carcinoma. Do you know of any direct evidence of that in women who have breastfed for a long time?
I am not aware of people having looked at that, but again, it is an attractive hypothesis.
You indicated that breastfeeding had an effect on maternal behaviour. Could you say something more about that? And a second question. The United States is going through major social changes. Many children of teenage mothers of lower socio-economic class are born out of wedlock, often without a father present, and the use of drugs (in particular, crack) has reached epidemic proportions. What is the benefit of breastfeeding for this group of mothers?
Dr. Garza has strong opinions on maternal behaviour, so I will ask him to respond to your first question. The issue here is that there are changes in the maternal brain as a result of breastfeeding that change the mother's responses to painful stimuli. Mothers become more placid.
The only thing I would add is that there are some very intriguing animal data suggesting that oxytocin, for example, may change maternal behaviour. It is very difficult to think that a hormone that has played such a basic role in animal physiology would not also have a similar impact on people. But of all the benefits-nutritional, immunologic, and bonding -the last is the least well documented and the least studied both in animals and in humans. A number of investigators around the world are taking a closer look at this. One symposium held in Europe about three years ago looked at the behavioural effects of hormones that we normally associate with lactation.
As a behavioural scientist myself, I think it is very attractive to think in terms of what breastfeeding does and how it could affect maternal behaviour, for example, through oxytocin acting on the brain. But I don't think there are any hard data that would actually support the notion that breastfeeding changes maternal behaviour. Just to carry out such a study would be very difficult. The data on bonding have been primarily related to the issue of immediate contact between the infant and the mother and have not really been related to breastfeeding, as such.
The point that you are making is correct. The hard data available are essentially nil. We are making an inference. I was very careful not to use the word bonding because of exactly the problems that you outlined. Bottle-feeding mothers do feel close to their infants, and what do we have as a measure of closeness? It's not easy.
On your second question, you posed the all-tooreal situation of the teenage mother in the United States. What do we recommend? Such young women are biologically capable of breastfeeding. The issue is whether we recommend it to them. Breastfeeding is done most effectively by women who are committed to it. Teenage pregnancy programmes around the country are giving these girls a lot of support, and some of the investigators are finding that these young women can successfully breastfeed with this kind of support. When you see that, you are seeing a whole lifestyle change, and they may be giving up some of the practices that got them pregnant in the first place. We would like to have a situation in which we could feel good about recommending breastfeeding.
Carol Bryant and colleagues did as controlled a study as you can on a teenage population under those circumstances. They randomly assigned young women to two groups. They educated the women in one group to breastfeed. In the other group, they supported the mothers in every other way but never mentioned breastfeeding. They measured the effects on the mother, and after one year, there was a clear difference. Those women who had breastfed had changed. They had established some self-esteem and had gotten hold of their lives, whereas the mothers who had not breastfed had not changed. They had not deteriorated, but they had not improved in their own self-image and some other behaviours.
So, I do not know whether we can make this a general recommendation. It requires a whole lot of support to happen well, and that is the kind of thing that Carol Bryant is doing.
I have been involved in some support for grassroots projects on mother-friendly workplaces. When we are thinking of policy, we should include schools as the teenage mothers' workplace. It is really amazing how much can be accomplished if teenage mothers can be encouraged to stay in school. Were you including sociocultural environment?
I was considering the support for breastfeeding in the mother's particular home environment. Did her husband or partner support it? Did her mother-inlaw, her mother, her family? I was thinking about various cultural environments. For example, upstate New York is pro-breastfeeding. Davis, California, is perhaps the classic pro-breastfeeding environment. In inner-city Baltimore, the breastfeeding rate is only 4%.
What are your feelings about osteoporosis in women who do not have such high levels of calcium intake as those in Janet King's studies? What do we advise women who are breastfeeding in the United States and in the United Kingdom who wish to give up dairy products because they are worried about colic in the baby? We have seen quite a few breastfeeding women give up drinking milk completely because of concern about fat in the diet. Do you feel that the 300 to 400 mg daily calcium intake in these women would be sufficient to sustain repletion?
The simple answer is that I don't know. There are a number of papers on women whose daily calcium intakes are 1,000 mg or more. They certainly have adequate calcium to make that repletion. I don't know of any study in which women with lower calcium intakes have been followed over a longer period. I am not sure how ethical it would be to randomly assign them to a calcium pill or no pill plus their usual intake. Certainly nobody has done a joint analysis of lactation history, usual calcium intake, and incidence of osteoporosis. You have hit a raw nerve, because I took calcium pills myself when breastfeeding, since I am a non-milk-drinker myself.
In the Gambia we found a small loss of bone calcium in the forearm. In women who were fully breastfeeding with no supplementation at all, there was a repletion before 12 months. There is an urgent need to follow at least some groups of women who are consuming low amounts of calcium. It doesn't have to be a trial, just an observational study.
Before closing this session on the impact of breastfeeding on fertility, I would like to ask Bishop McHugh to comment on a point that some of us were discussing earlier today: whether it is acceptable to the Catholic Church and to the Holy Father if a woman decides to breastfeed with the express intention of not getting pregnant, of delaying her next pregnancy, of spacing her family.
It is an easy answer. Yes, it is all right. There is no prohibition or inhibition on the part of the Church for a woman to use breastfeeding or the LAM (lactation amenorrhea method) as a method of spacing or delaying future births. In fact, it is our intent to encourage that. As Dr. Perez said, it very often correlates with the use of the natural methods of family planning, and indeed, many people in natural family planning today make a direct effort to combine breastfeeding with natural methods of family planning, as the early phase of deferring the next birth. There would be no prohibition by the Church to the use of breastfeeding to defer subsequent birth.
Thank you, Bishop McHugh. I think that is a very important point.
Could I follow up on that? I assume there would be no objection to the use of methods of detecting ovulation, if the people could develop better means. Natural family planning is based on one method, a rather crude method. Would there be any problems if there were better methods of detecting when ovulation occurs?
I would say no. As a matter of fact, at the earlier meeting on natural family planning, a lot of data on more technical methods were presented, but the more technical you get, the less useful it is to a population, especially to a third world population. There is a direct effort being made to find more accurate methods of predicting ovulation.