Spontaneous Abortion and Birth Order
- 1 January 1974
- journal article
- research article
- Published by Cambridge University Press (CUP) in Journal of Biosocial Science
- Vol. 6 (1), 23-41
- https://doi.org/10.1017/s0021932000009482
Abstract
Summary It is well established that, in general, pregnancies at advanced maternal ages or of advanced birth order are at greater risk of aborting spontaneously. It does not follow that each individual woman, as she proceeds through her reproductive life, becomes steadily more prone to abort. The present paper attempts to analyse evidence on how individual women's abortion probabilities vary during their reproductive lives. Statistical examination of the data suggests that: 1. A spontaneous abortion in a given birth rank is more likely than a live birth in the same rank to be followed by a further pregnancy. Abortion-prone women have more pregnancies than other women. 2. There is no significant overall tendency for spontaneous abortions to appear early or late in sibships even when account is taken of the reproductive compensation reported above. 3. Pathological examination of spontaneously aborted fetuses suggests that more (perhaps many more) than 10% of spontaneous abortions (e.g. those associated with trisomy and maternal isoimmunization) are causally associated with advanced maternal age or birth order. 4. The mean maternal age of spontaneously aborted fetuses which fail to grow in culture is higher than that of fetuses which are successfully cultured. One would infer: A. (from suggestions 1 and 2 above) that reproductive compensation (rather than a real birth order effect) is a major reason why abortion rates are higher at higher maternal ages and higher birth ranks; B. (from suggestions 2 and 3 above) that there must be another group of abortions, roughly equal in number, which are causally associated with low maternal age or early birth order. Little is known about this second group of reproductive casualties (those associated with low birth order or maternal age), but it is suggested that some have CNS malformations. I have made similar suggestions in regard to stillbirth and neonatal death.Keywords
This publication has 30 references indexed in Scilit:
- Inferences about Abortion from Foetal Mortality DataPopulation Studies, 1969
- Central nervous system malformation stillbirths, maternal age and birth orderAnnals of Human Genetics, 1969
- Mongolism, Delayed Fertilization and Sexual BehaviourNature, 1968
- An Analysis of Reproductive Patterns in an American IsolatePopulation Studies, 1965
- Parental Age and the OffspringThe Quarterly Review of Biology, 1964
- BIRTH ORDER AND MATERNAL AGE OF HOMOSEXUALSThe Lancet, 1962
- Pregnancy, Birth and AbortionMarriage and Family Living, 1959
- THE COMPLETED REPRODUCTIVE PERFORMANCES OF 161 COUPLES SELECTED BEFORE MARRIAGE AND CLASSIFIED BY ABO BLOOD GROUPAnnals of Human Genetics, 1957
- PATHOLOGY OF PREGNANCY SPONTANEOUS AND HABITUAL ABORTIONSObstetrical & Gynecological Survey, 1956
- The Categories of Abortion and Abortion‐Stillbirth SequencesBJOG: An International Journal of Obstetrics and Gynaecology, 1942