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A case of superfoetation in the rat is described and an estimate of the incidence of naturally occurring cases in a colony of Porton strain Wistar (LAC:P) rats rats is made (0-09-0-27% of litters born).
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Sexual chase was observed throughout pregnancy in hares permanently housed with a male. The incidence of oestrus followed by mating increased rapidly from Day 34 to day 38. Follicular growth was not interrupted; the mean number of large follicles increased at the end of pregnancy. Ovulation could be induced by hCG at any stage of pregnancy, but only on the last days by mating.
In brown hares, which are induced ovulators, sexual behaviour occurs episodically at the beginning of pregnancy. From Day 34 (length of pregnancy is 41 days), the frequency of sexual chases followed by mating, ovulation and fertilization increased and 59% of pregnant females presented a natural superfoetation. The pattern of circulating luteinizing hormone (LH), follicle-stimulating hormone (FSH), oestradiol and progesterone was studied in 13 pregnant females left permanently with a male, and in 10 females isolated from males around Day 20 of pregnancy. In the 2 groups FSH concentrations were high at the beginning and end of pregnancy. All females presented a peak value of FSH in the last 4 days of pregnancy, regardless of mating stimuli. This peak value was higher for females left permanently with a male than for isolated ones. Oestradiol concentrations fluctuated between 20 and 100 pg/ml, without any clear correlation with sexual behaviour, stage of pregnancy or profiles of other hormones. Prepartum matings occurred when progesterone values were still greater than 50 ng/ml; they were followed by a transient rise in LH and by a periovulatory progesterone secretion, with values above 100 ng/ml in the morning after mating. Such modifications of LH and progesterone were not detected before Day 34, suggesting that mating stimuli are not able to induce an LH surge at the beginning of pregnancy. After Day 34, mating can induce an LH surge, ovulation and superfoetation.
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Superfecundation is the fertilisation of two or more ova from the same cycle by sperm from separate acts of sexual intercourse. The term is also sometimes used to refer to the instances of two different males fathering fraternal twins, though this is more accurately known as heteropaternal superfecundation. This therefore leads to the possibility of twins also being half-siblings. This way of formation of multiply pregnancy aroused and it arouses still among doctors on whole world. This problem aroused large interest also among Polish doctors. For example, we found mention of superfecundation in first Polish medical journal, in Primitiae physico-medicae..., given in Leszno in years 1750-1753. Authors introduced relate opinion of superfecundation in aetiology of multiple pregnancies in historical aspect, as early as from Old Testament to present times as well as current state of medical knowledge of such a situation.
A case of biphasic temperature record is reported during the course of an ectopic pregnancy. Possible implications of this phenomenon may improve our understanding of the role of ovum transmigration and the endocrinological interaction of pregnancy with hormonal control of ovulation.
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