Spontaneous superfetation diagnosed in the first trimester with successful outcome. (1/8)

We report a twin pregnancy in which a 4-week discordance in size between the fetuses was identified in the first trimester. The discordance was maintained throughout the pregnancy, which was otherwise uneventful and resulted in the delivery of a live girl and boy.  (+info)

Preliminary results on plasma progesterone levels during pregnancy and superfetation in the hare, Lepus Europaeus. (2/8)

Peripheral plasma progesterone levels were studied in pregnant hares. A rise occurred at the beginning of pregnancy, followed by a plateau from Days 10 to 35, and then a drop during the days just before parturition. No significant differences were noted between progesterone levels in pregnancies initiated at the pre-partum oestrus and those from other oestrous periods.  (+info)

Anomalous litters in hybrid mice and the retention of spermatozoa in the female tract. (3/8)

Suspected superfetation was investigated in a Glasgow hybrid stock of mice. The male was removed either (i) a few days before parturition, or (ii) immediately after mating and on 23 and 25 occasions, respectively, a second litter was born. Members of the anomalous litters were inbred for 10 generations, but the incidence of supernumerary litters did not increase beyond 2-5%. The anterior part of over 500 reproductive tracts, at various stages of pregnancy and after parturition, were serially sectioned but a second set of embryos was not found. The second gestation was of normal length and superfetation was not therefore considered to be the cause of the anomalous litters. In two females, one non-pregnant and one pregnant, spermatozoa were found in the uterus and oviducts 8 days after mating and in distended uterine glands 15 days after mating respectively. It is concluded that the anomalous litters were derived from the fertilization of eggs ovulated at the post-partum oestrus by spermatozoa which had been retained in the female tract for at least 23 days.  (+info)

Interbirth interval and duration of pregnancy in hares. (4/8)

The possibility of inducing superfetation in hares by artificial insemination (AI) was investigated. AI performed on various days during the second half of gestation did not result in new pregnancies, but all ongoing pregnancies were terminated 1-4 days after AI. We suggest that copulation during the last week of pregnancy, common among captive hares, may have a similar effect to that of AI in terminating pregnancies and inducing early deliveries. Intervals between successive deliveries that are shorter than the normal duration of gestation do not necessarily indicate superfetation and this phenomenon may be rare among hares in captivity as well as in the wild.  (+info)

Discordant twins with the smaller baby appropriate for gestational age--unusual manifestation of superfoetation: a case report. (5/8)

BACKGROUND: Documentation of superfoetation is extremely rare in humans., The younger foetus has invariably been small for gestational age (estimated from the date of the last menstrual bleed) in all the cases reported in the literature. We report a case where the younger twin was of appropriate size for gestation. CASE PRESENTATION: The first of twins was of 32 weeks gestation and the baby was of appropriate size and development for the gestational age. The second twin was of 36 weeks gestation. Gestational age was estimated with the New Ballard score, x-ray of the lower limbs, dental age on x-ray, and ophthalmic examination. CONCLUSION: Bleeding on implantation of the first foetus probably helped demarcate the two pregnancies. Dental age and the New Ballard score can be used to diagnose superfoetation in discordant twins, when detailed first trimester ultra-sound data is not available.  (+info)

Gonadotrophins and sex steroids during pregnancy and natural superfoetation in captive brown hares (Lepus europaeus). (6/8)

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.  (+info)

Gestational age in twins. (7/8)

Dubowitz et al. have offered a scoring system for estimating the gestational age of newborn babies. If the system is applied to twin pairs, the heavier twin is generally estimated to have a greater gestational age than the lighter one. Previously this has been interpreted as a flaw in the scoring system. However, it may well be that in some twin pairs the gestational ages are slightly different and that therefore, the heavier twin would be expected to have a greater gestational age. Such cases would arise through superfecundation (the formation of two zygotes from different coitions). Superfecundation can be proved only in rare case (those with two fathers). It can be argued that the rarity of such cases is accounted for by the rarity with which women expose themselves to the risk of bearing such twins (and by the improbability of detection), rather than by the rarity of superfecundation. It is inferred that superfecundation by the same man is relatively common and that therefore dizygotic twins quite often have different gestational ages. The scoring system of Dubowitz can be tested for bias by submitting monozygotic pairs to it: the association between weight and estimated gestational age should be absent in such pairs. If the system proves free of such bias, then a finding first reported here will assume some interest: it is that in opposite-sexed twin pairs, the male is significantly more often assessed as having the greater gestational age. It is suggested that this finding should be provisionally accepted as evidence for the hyopthesis that male zygotes are formed earlier than females.  (+info)

Oestrous behaviour, follicular growth and ovulation during pregnancy in the hare (Lepus europaeus). (8/8)

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.  (+info)