Once upon a time, when reading about kangaroos, I read about a reproduction phenomemon that I'd never previously encountered. It is called "Fetal Resorption". Apparently when times are good, a female kangaroo can have a sort of "pipeline" of offspring in production. One is growing in the womb while two others of different ages (a year apart) are in the pouch. It works well; kangaroos are not an endangered species.
Well, when times are bad the female kangaroo's biology shuts down the pipeline quite abruptly, by not only cutting off the flow of nutrients to the one growing in the womb, but actually and actively and literally "sucking the life out of it". The fetus is entirely CONSUMED by the womb. Nature is thriftily returning to the female kangaroo the "investment" in biological resources that had been given to the fetus, before "times became bad".
Some time after learing about "fetal resorption", I found out that it sometimes happens that other animals do it, too, humans included. Today I happened to think, "Biological redirection of this magnitude is always hormone-based. What is the cause of fetal resorption?"
A little Googling later, I can invite you to see the link below. It is about dogs and not humans, but I don't know that the fundamental mammalian reproductive hormonal biology is hugely different in this matter. So, see this quote: "The most common causes of fetal resorption are inadequate progesterone levels ..."
OKAY, suppose we deliberately seek to cause progesterone levels to drop? Progesterone is just a hormone that can be "latched onto" and rendered ineffective by an appropriately designed molecule ("drug"). This means (simplistically, I'm sure!!!) that a woman who wishes to use this Idea as a birth control method merely takes a pill that puts this drug into her system. Her effective progesterone level dives through the basement. If she is RECENTLY pregnant, fetal resorption begins. NO MESS! (After more than a couple of weeks of pregnancy, a miscarriage can be expected.) If she is not pregnant, well, another Googling failed to find any health problems associated with a temporary too-low progesterone level. There might be some that I couldn't find, of course.
Remember that in a few days after taking this pill, the drug will have been cleared from her system, and her progesterone level should return to normal.-- Vernon, Oct 21 2005 Causes of fetal resorption http://www.vetinfo.com/dfetsorb.htmlAs mentioned in the main text. [Vernon, Oct 21 2005] Bruce Effect http://en.wikipedia.org/wiki/Bruce_effect [bungston, Oct 21 2005] Poly (I) Poly (C12U) http://www.ncbi.nlm...46771&dopt=Abstract [reensure, Oct 21 2005] Can Abortions Cause Breast Cancer? http://www.cancer.o...o_Breast_Cancer.aspAs referenced in an annotation [Vernon, Apr 04 2006] I think the fundamental difference is menstruation. Not all mammals do. I think in humans, unsupported pregnancies are sloughed along with the uterine lining with the menses. Other mammals resorb the uterine lining and so can presumably absorb other associated tissue, including fetal tissue. Mice can resorb pregnancies that are well along if exposed to the smell of an unfamiliar male - the "Bruce Effect" (linked).
So no bun for the idea, but it is interesting to speculate on the evolutionary reasons for a process as wasteful as menstruation.-- bungston, Oct 21 2005 Such a compound exists (not as direct as in the Idea) but we seem to have evolved diversity to prevent the rates of resorption seen in other species. <link>-- reensure, Oct 21 2005 Progesterone protects women from cancer. Even a few days of low progesterone will probably be very dangerous.
There's an argument as to whether abortion increases cancer risk. What IS proven is that carrying a child to FULL term does reduce cancer risks.
This procedure may well be more dangerous to the mother than mechanical abortions, especially if the mother plans to never have children.-- Madai, Oct 21 2005 Some data I found in an abortion-debate forum, regarding abortions and breast cancer:
Lash TL. Fink AK. Null association between pregnancy termination and breast cancer in a registry-based study of parous women. International Journal of Cancer. 110(3):443-8, 2004 Jun 20. “Studies suggesting a positive association between pregnancy termination and breast cancer risk have often been of retrospective case-control design, so subject to selection and recall biases. We undertook a registry-based analysis with minimal selection bias and prospective record-based ascertainment of terminations. The source population comprised Massachusetts women with a record of giving birth between 1987 and 1999 in the Massachusetts Vital Statistics Registry. Primary breast cancer cases were 25-55 years old at diagnosis between 1988 and 2000 and had a record of the diagnosis in the Massachusetts Cancer Registry. We matched 3 controls to each case on maternal age, year of giving birth and birth facility. Information on terminations (induced and spontaneous) before the birth of record, the matched factors and potential confounders were collected from the birth certificate. After adjustment for the matched factors, age, parity and maternal and paternal education, the odds ratio associating any termination history with breast cancer risk equaled 0.91 (95% CI = 0.79-1.05). The marginally protective adjusted odds ratio largely derived from a protective effect among women with parity equaled to 1 (OR for any termination = 0.68; 95% CI = 0.45-1.03), suggesting a protective effect of terminated pregnancy among women with one live birth. Copyright 2004 Wiley-Liss, Inc.”
Beral V. Bull D. Doll R. Peto R. Reeves G. Collaborative Group on Hormonal Factors in Breast Cancer. Breast cancer and abortion: collaborative reanalysis of data from 53 epidemiological studies, including 83?000 women with breast cancer from 16 countries. [Journal Article. Multicenter Study. Review] Lancet. 363(9414):1007-16, 2004 Mar 27. BACKGROUND: The Collaborative Group on Hormonal Factors in Breast Cancer has brought together the worldwide epidemiological evidence on the possible relation between breast cancer and previous spontaneous and induced abortions. METHODS: Data on individual women from 53 studies undertaken in 16 countries with liberal abortion laws were checked and analysed centrally. Relative risks of breast cancer--comparing the effects of having had a pregnancy that ended as an abortion with those of never having had that pregnancy--were calculated, stratified by study, age at diagnosis, parity, and age at first birth. Because the extent of under-reporting of past induced abortions might be influenced by whether or not women had been diagnosed with breast cancer, results of the studies--including a total of 44000 women with breast cancer--that used prospective information on abortion (ie, information that had been recorded before the diagnosis of breast cancer) were considered separately from results of the studies--including 39000 women with the disease--that used retrospective information (recorded after the diagnosis of breast cancer). FINDINGS: The overall relative risk of breast cancer, comparing women with a prospective record of having had one or more pregnancies that ended as a spontaneous abortion versus women with no such record, was 0.98 (95% CI 0.92-1.04, p=0.5). The corresponding relative risk for induced abortion was 0.93 (0.89-0.96, p=0.0002). Among women with a prospective record of having had a spontaneous or an induced abortion, the risk of breast cancer did not differ significantly according to the number or timing of either type of abortion. Published results on induced abortion from the few studies with prospectively recorded information that were not available for inclusion here are consistent with these findings. Overall results for induced abortion differed substantially between studies with prospective and those with retrospective information on abortion (test for heterogeneity between relative risks: chi2(1) =33.1, p<0.0001). INTERPRETATION: Pregnancies that end as a spontaneous or induced abortion do not increase a woman's risk of developing breast cancer. Collectively, the studies of breast cancer with retrospective recording of induced abortion yielded misleading results, possibly because women who had developed breast cancer were, on average, more likely than other women to disclose previous induced abortions. [References: 85]
Palmer JR. Wise LA. Adams-Campbell LL. Rosenberg L. A prospective study of induced abortion and breast cancer in African-American women. Cancer Causes & Control. 15(2):105-11, 2004 Mar. OBJECTIVE: There continues to be controversy about whether induced abortion influences the risk of breast cancer. Because case-control studies of this relation are subject to recall bias, there is a need for prospective data. Further, there has been little study of abortion and breast cancer in African-American women. We assessed the relation of abortion to risk of breast cancer in a prospective follow-up study of African-American women. METHODS: Black Women's Health Study participants have been followed by mailed questionnaires every two years since enrollment in 1995. Participants reported 348 incident breast cancers during 205,983 person-years of follow-up. Women who had an induced abortion were compared with women who had never had one, with nulliparous and parous women analyzed separately. Incidence rate ratios (IRR) with two-sided 95% confidence intervals (CI) were derived from Cox regression models that controlled for age, age at first birth, number of births, history of spontaneous abortion, and other factors. RESULTS: Among nulliparous women, the IRR for any induced abortion relative to none was 0.9 (95% CI = 0.5-1.4), and among parous women, the comparable IRR was 1.1 (95% CI = 0.8-1.4). Risk did not vary by number of abortions, age at first abortion, age at diagnosis or a family history of breast cancer in either nulliparous or parous women. CONCLUSIONS: Our findings indicate that induced abortion does not increase breast cancer risk in African-American women.
ACOG Committee on Gynecologic Practice. ACOG Committee Opinion. Number 285, August 2003: Induced abortion and breast cancer risk. Obstetrics & Gynecology. 102(2):433-5, 2003 Aug. The purpose of this Committee Opinion is to provide a review of recent studies regarding the potential relationship between induced abortion and subsequent breast cancer and to discuss methodologic challenges in this field of study. The American College of Obstetricians and Gynecologists' Committee on Gynecologic Practice concludes that early studies of the relationship between prior induced abortion and breast cancer risk have been inconsistent and are difficult to interpret because of methodologic considerations. More rigorous recent studies argue against a causal relationship between induced abortion and a subsequent increase in breast cancer risk.
Paoletti X. Clavel-Chapelon F. Induced and spontaneous abortion and breast cancer risk: results from the E3N cohort study. International Journal of Cancer. 106(2):270-6, 2003 Aug 20. Recent reviews reach conflicting conclusions on breast cancer risk after spontaneous or induced abortion. E3N is a large-scale cohort study collecting detailed information on environmental and reproductive factors. We investigated the relation between breast cancer and a history of induced and/or spontaneous abortion, using the data from the 100,000 women aged 40-65 at entrance in 1990. Among them, over 2,600 new invasive breast cancers had been diagnosed by June 2000. Multivariate analysis, adjusted for known potential confounders, showed no association between a history of induced abortion and breast cancer risk either in the whole population (relative risk [RR] = 0.91, 95% confidence interval [CI] 0.82-0.99) or in subgroups defined by parity or by menopausal status. Overall, the association between spontaneous abortion and breast cancer was not significant (RR = 1.05, 95% CI 0.95-1.15). However, there is a suggestion of increased risk with increased number of miscarriages (RR = 1.20, 95% CI 0.92-1.56 after 3 or more). Moreover, an interaction with menopausal status was observed. In premenopause, the risk decreased with increasing number of spontaneous abortions, whereas it increased in postmenopause. Among nulliparous and parous women, the relative risk estimates were respectively equal to 1.16 (95% CI 1.04-1.30, p trend < 0.0008) and 1.14 (95% CI 1.01-1.28, p trend = 0.005). Premenopausal breast cancer, on the other hand, appeared to be less frequent in women who had had repeated miscarriages. We conclude that there is no relationship between breast cancer and induced abortion but that an association with spontaneous abortion is possible and may depend on menopausal status. Copyright 2003 Wiley-Liss, Inc.
Becher H. Schmidt S. Chang-Claude J. Reproductive factors and familial predisposition for breast cancer by age 50 years. A case-control-family study for assessing main effects and possible gene-environment interaction. International Journal of Epidemiology. 32(1):38-48, 2003 Feb. BACKGROUND: The effect of environmental/lifestyle factors on breast cancer risk may be modified by genetic predisposition. METHODS: In a population-based case-control-family study performed in Germany including 706 cases by age 50 years, 1381 population, and 252 sister controls, we investigated main effects for environmental/lifestyle factors and genetic susceptibility and gene-environment interaction (G x E). Different surrogate measures for genetic predisposition using pedigree information were used: first-degree family history of breast or ovarian cancer; and gene carrier probability using a genetic model based on rare dominant genes. Possible G x E interaction was studied by (1) logistic regression using cases and population controls including an interaction term; (2) comparing results using sister controls and population controls; (3) case-only analysis with logistic regression and (4) a mixture logistic model. RESULTS: Familial predisposition showed the strongest main effect and the estimated gene carrier probability gave the best fit. High parity and longer duration of breastfeeding reduced breast cancer risk significantly, a history of abortions and age at menarche showed no significant effect. We found significant G x E interaction between parity and genetic susceptibility using different surrogate measures. In women most likely to have a high genetic susceptibility, high parity was less protective. Later age at menarche was protective in women with a positive family history. No evidence for G x E interaction was found for breastfeeding and abortion. CONCLUSIONS: These findings corroborate results from other studies and provide further evidence that the magnitude of protection from parity is reduced in women most likely to have a genetic risk in spite of the limitations of using surrogate genetic measures.
Mahue-Giangreco M. Ursin G. Sullivan-Halley J. Bernstein L. Induced abortion, miscarriage, and breast cancer risk of young women. Cancer Epidemiology, Biomarkers & Prevention. 12(3):209-14, 2003 Mar. Early studies of breast cancer raised substantial concern regarding risk associated with induced abortion and miscarriage. Literature reviews suggest that study findings depend heavily on the comparison group and that the use of parous women as a reference group for nulliparous women may artificially inflate risk. To examine the individual effects of induced abortion and miscarriage on breast cancer risk of parous and nulliparous women, 744 patients < or =40 years of age and diagnosed from 1983-1988 were matched by parity, age, and race with controls living in the same neighborhood in Los Angeles County. In-person interviews were conducted to obtain a detailed reproductive history. Risk estimates were obtained by conditional logistic regression using nulligravid women as the reference group for nulliparous women with a history of incomplete pregnancy and parous women with no incomplete pregnancies as the reference group for parous women with a history of incomplete pregnancy. Breast cancer risk of parous women was unrelated to a history of miscarriage or induced abortion. Breast cancer risk was reduced among nulliparous women with a history of induced abortion relative to nulligravid women, although the risk estimate was imprecise. Risk declined as the number of induced abortions increased (P = 0.04). Our results do not support the hypothesis that induced abortion or miscarriage increase the breast cancer risk of young women
Erlandsson G. Montgomery SM. Cnattingius S. Ekbom A. Abortions and breast cancer: record-based case-control study. International Journal of Cancer. 103(5):676-9, 2003 Feb 20. It has been suggested that abortions leave the breast epithelium in a proliferative state with an increased susceptibility to carcinogenesis. Results from previous studies of induced or spontaneous abortions and risk of subsequent breast cancer are contradictory, probably due to methodological considerations. We investigated the relationship between abortions and subsequent breast cancer risk in a case-control study using prospectively recorded exposure information. The study population comprised women recorded in the population-based Swedish Medical Birth Register between 1973-91. Cases were defined by linkage of the birth register to the Swedish Cancer Register and controls were randomly selected from the birth register. From the subjects' antenatal care records we abstracted prospectively collected information on induced and spontaneous abortions, as well as a number of potential confounding factors. Relative risk of breast cancer was estimated by odds ratios (OR) with 95% confidence intervals (95% CI). A reduced risk of breast cancer was observed for women with a history of at least 1 compared to no abortions (adjusted OR = 0.84, 95% CI = 0.72-0.99). The adjusted OR decreases step-wise with number of abortions to 0.59 (95% CI = 0.34-1.03) for 3 or more compared to no abortions. The patterns are similar for induced and spontaneous abortions. In conclusion, neither a history of induced nor spontaneous abortions is associated with an increased risk of breast cancer. Our data suggest a protective effect of pregnancies regardless of outcome. Copyright 2002 Wiley-Liss, Inc.
Ye Z. Gao DL. Qin Q. Ray RM. Thomas DB. Breast cancer in relation to induced abortions in a cohort of Chinese women. [Clinical Trial. Journal Article. Randomized Controlled Trial] British Journal of Cancer. 87(9):977-81, 2002 Oct 21. The possible influence of induced abortion on breast cancer risk was assessed in a cohort of 267 040 women enrolled in a randomised trial of breast self-examination in Shanghai, China. Based on answers to a baseline questionnaire, subsequent breast cancer risk was not significantly associated with ever having an induced abortion. After adjustment for potential confounders, the relative risk estimate was 1.06 (95% C.I.: 0.91, 1.25), and there was no trend in risk with number of abortions. Analysis of data from more detailed interviews of 652 cases and 694 controls from the cohort yielded similar results. There was also no overall increase in risk in women with induced abortion after first birth. Few women had undergone an abortion after 13 weeks gestation or before their first child. Although increases in risk were observed in such women, they were not statistically significant and could have been due to recall bias. Abortions as they have been performed in China are not an important cause of breast cancer.
Davidson T. Abortion and breast cancer: a hard decision made harder. Lancet Oncology. 2(12):756-8, 2001 Dec. Over recent years, concerns have been raised about a possible causal relation between induced abortion and subsequent breast cancer. The abrupt hormonal changes associated with termination of pregnancy may induce changes in breast epithelial cells at a stage when they are not fully differentiated and therefore more vulnerable to later development of breast cancer. This review examines the published evidence supporting and refuting this hypothesis and concludes that there are, to date, insufficient data to justify warning women of future breast-cancer risk when counselling them about abortion. [References: 28]
Newcomb PA. Mandelson MT. A record-based evaluation of induced abortion and breast cancer risk (United States). Cancer Causes & Control. 11(9):777-81, 2000 Oct. OBJECTIVE: Previous studies of induced abortion and breast cancer may have been limited by differential reporting of abortion history. We conducted a population-based case-control study to evaluate abortion (both induced and spontaneous) and breast cancer risk. METHODS: All study subjects were aged 20-69 years and members of Group Health Cooperative of Puget Sound (GHC). Incident invasive breast cancer cases (n = 138) were identified from the linkage between the GHC enrollment file and the Seattle-Puget Sound SEER Cancer Registry. Controls (n = 252) were randomly selected from GHC enrollment files and matched to cases on age and enrollment period. All subjects had to have been enrolled at GHC for the 2 years preceding diagnosis (cases) or reference (controls) date. The unified medical record of each case was abstracted for pregnancy history, including prior induced and spontaneous abortions, menopause status, height and weight, screening practices, and other risk factors. RESULTS: Compared to all women who had never had an induced abortion, the multivariate adjusted relative risk of breast cancer in women with an induced abortion was 0.9 (95% confidence interval 0.5-1.6). This risk was similar in parous women, and nulliparous women. There was no association between spontaneous abortion and breast cancer risk. CONCLUSIONS: These results do not support a relation between induced abortion and breast cancer incidence.
Tang MT. Weiss NS. Malone KE. Induced abortion in relation to breast cancer among parous women: a birth certificate registry study. Epidemiology. 11(2):177-80, 2000 Mar. We wished to assess the relation of induced abortion to the subsequent incidence of breast cancer among parous women, using a design that would prevent the possibility of differentially complete reporting of abortion history by women with breast cancer and controls. Our study was conducted within a cohort of women who gave birth to a child during 1984-1994 while residing in 13 counties of western Washington. Cases were women from the cohort diagnosed with breast cancer between 1984 and 1994. From the remaining cohort members, five controls were matched to each woman with breast cancer by year of index birth (ie, the last child born before breast cancer diagnosis) and by age at delivery. We categorized 463 cases and 2,201 controls according to history of induced abortion as recorded on the index birth certificate. The risk of breast cancer was not found to be associated with a prior induced abortion (estimated relative risk (RR) = 0.9, 95% confidence interval (CI) 0.7-1.2). These results suggest that an induced abortion, if followed at some later time by pregnancy and childbirth, does not increase a woman's risk of breast cancer.
{from link} Before 1973, induced abortions were illegal in much of the United States. Therefore, when researchers asked about a woman's reproductive past, women may not have been comfortable disclosing the fact that they had an illegal abortion. Even though abortion is now legal, it is still a very personal, private matter that many women are hesitant to talk about.
Studies have shown that healthy women are less likely to report their histories of induced abortions. In contrast, women with breast cancer are more likely to accurately report their reproductive histories because they are searching their memories for anything that may have contributed to their disease.
The likelihood that women who have breast cancer will give a more complete account of their abortions than women who do not have breast cancer is called "recall bias," and it can seriously undermine the accuracy of study results.
Most early studies of abortion and breast cancer used a case-control study design, one that is very prone to recall bias. In these studies, women with and without breast cancer were asked to report past abortions. The frequency of abortions in women with breast cancer and the disease-free controls were then compared. It is likely that the small increases in breast cancer risk observed in many of these studies were not authentic findings because of recall bias.
A prospective study design is stronger and less prone to bias. In this type of study, a group of women who are cancer-free are asked about their past abortions and then are observed over a period of time to see if a new cancer occurs. In this type of study, there is no chance that having the disease will influence a woman's memory of past abortions or willingness to report past abortions.
Some prospective studies have addressed the problem of recall bias by using innovative ways to document induced abortions. For example, a recent study used birth certificates of children born to women with breast cancer to identify women who had had induced abortions. (The number of previous pregnancies and their outcomes were listed on these birth certificates.) This study found no increase in breast cancer risk in women whose abortion is followed by a live birth.
The largest, and probably the most reliable, single study of this topic was conducted during the 1990s in Denmark, a country with very detailed medical records on all its citizens. In that study, all Danish women born between 1935 and 1978 (1.5 million women) were linked with the National Registry of Induced Abortions and with the Danish Cancer Registry. So all information about their abortions and their breast cancer came from registries, was very complete, and was not influenced by recall bias.
After adjusting for known breast cancer risk factors, the researchers found that induced abortion(s) had no overall effect on the risk of breast cancer. The size of this study and the manner in which it was conducted provides substantial evidence that induced abortion does not affect a woman's risk of developing breast cancer.
Recent research has confirmed that the type of study likely plays a role in what is found. A review of the previous studies on this issue (see below), covering tens of thousands of women, showed that women followed in prospective studies (which are less prone to bias) had no increased breast cancer risk if they had had an abortion. Retrospective (case-control) studies, on the other hand, pointed to a slight increase in risk.-- Vernon, Apr 04 2006 random, halfbakery