Morning Sickness and Breast Cancer

Morning sickness has always been a puzzle and there are almost as many theories as there are sufferers.

Amongst some of the most popular theories are:

• An increase in the circulating level of the hormone estrogen. Estrogen levels may increase by 50-100 fold during pregnancy
• Low blood sugar during the early phases of pregnancy
• An increase in progesterone relaxes the muscles in the uterus, which prevents early childbirth, but may also relax the stomach and intestines, leading to excess stomach acids
• An increase in human chorionic gonadotropin
• An increase in sensitivity to odors, which in turn overstimulates normal triggers to nausea

I have always been interested in the idea that it is a device to protect the baby from dietary toxins. This theory was expressed very eloquently by Margie Profet, who suggested that eating vegetables may also be a factor. Vegetables produce a small amount of toxins to deter insect infestation and while these toxins are normally harmless to adult humans, they are potentially dangerous to the baby. It is also impressive that morning sickness is usually at its worst in the first trimester, when the baby is extremely sensitive to many kinds of toxins. It would be nice if Margie's theory turns out to be correct. She was largely ignored by specialists in reproduction because she was not one, and a the time did not have an advanced degree.

So I was very interested to see some research from the University of Buffalo that was presented last week at the Society for Epidemiologic Research's Annual Meeting in Boston. The epidemiologists found that women who had morning sickness may have a 30 percent lower risk of developing breast cancer later in life than mothers-to-be who went through pregnancy without any nausea.

The study was based on data from participants in the Western New York Exposure and Breast Cancer Study, a population-based case-control study of breast cancer conducted in women 35-79 from two Western New York counties between 1996 and 2001.

The analysis compared extensive data on pregnancy-related conditions from 1,001 women with primary breast cancer and 1,917 women without breast cancer matched to cases by age and race who served as controls.

The data presented suggest that the lower risk of developing breast cancer observed with nausea and vomiting was stronger as the symptoms became more severe, or persisted longer into pregnancy. A modest trend toward increased cancer risk was seen in premenopausal women who gained more than 40 pounds during pregnancy, compared to those who gained less than 23 pounds but the trend did not reach statistical significance.

Perhaps the link has to do with sensitivity to estrogen.

But the other possibility is that the nausea and vomiting not only expel toxins that may harm the baby. but also toxins that may eventually increase a woman's risk of breast cancer. And why might three months of vomitinj make the difference?

Because one of the reasons for weight gain during pregnancy is a subtle change in the intestinal absorption of certain nutrients that the baby needs.

Comments

[Carol]

RP--
Thanks for trying to make me feel better. Having experienced this whole thing first hand and still being amazed at the changes that are occurring with my body, I bet there are many, many factors and not just one.

[Richard Petty]

Dear Carol,

I am sure that you are correct, and the precise group of causes will undoubtedly vary from woman to woman.

But one of the reasons that I so like the toxin/protection theory is that we seem to be the only creatures that get morning sickness, and in most people it also just happens to coincide with the most vulnerable period of brain development. Something else that sets us apart from most other species.

Doctors who came for training from far flung corners of the former Empire, would often comment that morning sickness was fairly uncommon in sub-Saharan Africa ad the Indian subcontinent. I could not find any credible research to back up those observations. But if true, it might be that less nourished people cannot afford to vomit the little food that they have. Or perhaps their food contains fewer toxins that trigger the defense systems into action.

There are a couple of interesting papers:
the first a review of the data that morning sickness if adaptive and prophylactic:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=10858967

The second which did not find an association between no morning sickness and fetal abnormalities, but admits to being limited and needing replication:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=15329830

I do hope that it stops soon!

All the best,

RP