The aim of this work was to evaluate the relationship between follicular size at the time of oocyte retrieval, and the subsequent oocyte competence to be fertilized and to develop in vitro. All the obtained oocytes were classified according to the corresponding volume of aspirated follicular fluid. Aspirated volume of follicular fluid <2 ml corresponded to a follicular diameter <16 mm and constituted the small size group. Volume of follicular fluid from 2 to 6 ml corresponded to a diameter from 16 to 23 mm and constituted the medium size group. The large size group contained follicles with diameter >23 mm and corresponded to an aspirated volume of follicular fluid of >6 ml. A progressive and significant increase in the rates of oocytes with a first polar body was observed from the small size group to the other groups and from the medium to the large size group: 75.3, 85.9 and 95.3% respectively. After classical in-vitro fertilization (IVF), significantly better rates of fertilization and development were obtained in the medium size group compared to the two other groups. Moreover, a positive relationship was observed between follicular diameter and rates of embryos scored as 'good' when oocytes were fertilized by intracytoplasmic sperm injection (ICSI). These results demonstrated that follicular size is positively related to the oocyte ability to be fertilized and to develop. Although oocytes from small follicles gave lower percentages of development probably due to partial oocyte incompetence, they allowed an increase in the total number of embryos scored as 'good'.

Ovariectomized rats were given hormonal treatment mimicking progestational ovarian secretions. At maximal uterine sensitivity, the luminal epithelium was squeezed out of one or both horn(s) transected at the isthmus. Simultaneous bilateral scratching and saline injection induced virtually no response in stripped horns while contralateral intact horns exhibited a maximal decidual reaction (DCR). The luminal epithelium regenerated after ablation and a 65% DCR was again elicited after 9 days. The inability of de-epitheliated horns to decidualize was not overcome by intraluminal injections of the supernatant or sediment of the 60 000 g homogenate of epithelium, PGF-2 alpha, PGE-2, arachidonic acid or histamine. Detachment of the epithelium without removal also prevented DCR induction. These results indicate that the luminal epithelium is an obligatory transmitter of the stimulus to DCR and cannot be by-passed by trauma. Release of the appropriate epithelial message to the stroma requires local preservation of membrane relationships between both tissues.

The fertilization rates observed in 122 attempts at in-vitro fertilization were examined in relation to sperm characteristics assessed by visual and automated screening. Using linear regression analysis, a significant correlation was found between the fertilization rate and (i) evaluations in fresh semen sperm concentration, percentages of sperm motility, vitality and normal morphology and velocity, (ii) measurements in swim-up preparations of percentages of sperm motility, vitality and morphology, velocity and amplitude of lateral head displacement. No significant correlation was found between the fertilization rate and any of the parameters studied in 24-h-old swim-up suspensions. Analysis by multiple variable stepwise linear regression showed an optimal correlation (R6 = 0.62) between the observed fertilization rate and theoretical calculation obtained from the following predictive function: fertilization rate = -0.3 + (0.008 x swim-up motility) + (0.004 x normal sperm morphology in fresh semen). Introduction of kinematic characteristics studied by automated screening improved the multiple correlation between the calculated and observed fertilization rate in cases of normal or mildly defective semen. Because of the limited availability of motile spermatozoa, automated analysis could not supersede classical sperm analysis in cases of more severe sperm defects.

Ovariectomized rats were treated with oestradiol-17 beta and/or progesterone to mimic the hormonal parameters inducing uterine sensitivity for implantation. The degree of pinocytosis of trypan blue and ferritin in the endometrial cells was examined. Significant epithelial pinocytosis of trypan blue occurred after a 3-day treatment of progesterone, and uptake was independently increased by priming with oestrogen and by oestradiol given on the 3rd day of progesterone treatment. Progesterone treatment caused uptake of ferritin by the epithelial cells; in control animals epithelial and stromal cells were involved. Oestrogen priming enhanced ferritin absorption, while 'nidatory' oestrogen had no effect. Oestradiol given alone completely blocked pinocytosis of both intraluminally injected substances.

One hundred forty-six embryo transfers were carried out in the In Vitro Fertilization (IVF) Clinic at St. Pierre Hospital, Brussels, between November 1983 and February 1985. In each of these cases a series of characteristics of the replacement procedure was systematically recorded. Analysis of these data in relation to pregnancy rates indicated that no significant differences appeared among three different operators, the absence or occurrence of cervical bleeding and subjective evaluation of the procedure were related to the chances of establishing a pregnancy, and the duration of replacement had no influence on the outcome of trials. A prospective randomized study of 100 replacements showed that no better pregnancy rate was obtained by placing patients in the knee-to-chest rather than the dorsal position and the addition of a rigid external sleeve to the catheter did not provide any advantage. A simplified method of replacement is thus advocated.

Because of endopolyploidy, cell kinetics in decidual growth are best studied by cytophotometric methods. This technique was applied to smears of nuclei isolated from decidualizing endometrial stroma at various moments after uterine scratching in hormonally prepared rats. After a 48-hr lag period, the production of polyploid nuclei was accelerated. At its maximal development (96 hr), the decidual tissue contained few cells other than polyploid cells, the highest level attained being 32c. During decidualization, there was a progressive increase in labelling with [3H]thymidine and in mitotic indices up to the 3rd day. It is suggested that endopolyploidy results in this case from bypassing mitosis by cells lacking some rate-limiting metabolic factor indispensable to the mitotic phase.

In rodents, decidualization produces large endopolyploid cells. Amongst the various endocycles which have been demonstrated in animals and plants, different modes of DNA replication have been characterized: either total reproduction of all DNA types, or else, underreplication or amplified synthesis affecting specific parts of the genome. A double labelling method was used to determine to which of these categories the case of decidual cells belongs. A mixture of purified DNA from hormonally-stimulated control endometrium labelled by 3H-thymidine and from decidua labelled by 14C-thymidine was ultra-centrifuged to equilibrium in a Cs2 SO4-Ag gradient. Optical density at 260 nm and 14C/3H ratio were evaluated in serial fractions along the gradient. Since the 14C/3H ratio did not significantly vary along the gradient, it may be concluded that in the case of decidual cells, endopolyploidy corresponds to uniform replication of all nuclear DNA.

Cell kinetics in the uterine epithelium of ovariectomized rats were studied after uterine distension and/or an oestradiol injection, by cumulative 3H‐TdR labelling and percentage of labelled mitoses (PLM). With both methods it was found that distension shortens the total cell cycle at the expense of G1 more than does oestradiol. Both treatments act in a cumulative manner since the greatest reduction in Tc is observed after distension plus oestradiol. PLM curves showed that distension and/or oestradiol induce a 30% reduction in S phase duration. The evolution of percentages of labelled cells and colchicine‐blocked mitoses after these treatments confirms their additive effects and indicates that the mitogenic action of oestradiol is delayed compared to that of distension. It is suggested that these factors stimulate epithelial cell division in the uterus through partly different metabolic channels.