Fetal examinations

Visceral Fetal Examinations. The examination of the abdominal and thoracic viscera of fetuses is performed either fresh without fixation ( Staples technique ) or after Bouin s fixation by making freehand razor blade sections ( Wilson s technique Wilson, 1965). Both techniques have advantages. The fresh examination technique, which may require less training for thorough proficiency, provides a more easily interpreted view of heart anomalies. The examination must be performed on the day the dam is terminated, however, so having a large number of litters to examine in one day requires that a large team of workers be committed to the task. 

The fetuses are then examined. Full details of fetal examination are provided in other chapters of this book some techniques are performed on fresh fetuses, while other techniques require prior fixation of the fetuses. For rodents, one half of the fetuses in each litter should be examined for soft tissue (visceral) changes the remainder should be examined for skeletal changes. Rabbit fetuses should be examined for both soft tissue and skeletal abnormalities the heads from half of the fetuses should be examined by serial sectioning, with skeletal examination conducted on the remainder of the fetus. 

Embryotoxicity (fetal examinations) and postnatal development assessed in the same study Three segment strategy (fertility, embryotoxicity, pre- and postnatal development)... 

The caesarean subgroup is used for fetal examinations and routine teratology investigations as described in Chapters 12, 16, and 20. 

Each fetus is examined for external defects. Fetal examinations are performed under low power magnification. 

The mean and standard deviation are calculated for all parameters where feasible, using the litter as the basic sample unit. For fetal examination data, the group mean number and percentage incidence of affected fetuses with each type of finding are calculated. 

Due to the small size of the mouse, fetal examinations should be performed using a stereo dissecting microscope. 

If complete fetal examinations are included (see Subheading 6.6), the results of preliminary studies may also allow women of childbearing potential to be included in clinical trials before the conduct of definitive studies (8) (see Note 1). 

Blood can be taken from fetuses at necropsy by cardiac puncture before fetal examination. It is also possible to take, from satellite litters, fetal blood or amniotic fluid during gestation (i.e., day 19 of gestation). The fetal blood is pooled by litter to obtain a sufficient plasma volume for analyzes. 

Aloka Pro Sound SSD 4000 used for ultrasound examinations. For pregnancy confirmation, a 10 MHz linear probe (UST5542) is used. For fetal examinations, a 7.5 MHz probe (UST 5524) or 5 MHz convex probe (UST 992-5) is used depending on the size of the fetus. 

The fetus is stored in 50% glycerine during the fetal examination phase then transferred to 100% glycerine for archiving. 

To conduct fetal examinations adequately, it is important to have a clear idea of the normal anatomy. Every effort should be made to assess the anatomy in exactly the same way for every fetus, applying identical criteria to distinguish normal from abnormal. The priority should be ensuring consistency within each laboratory so that valid comparisons can be made between treated and control animals, both within and between studies conducted in that laboratory. It takes a lot of experience to be confident that you can spot the difference. ... 

Key words Fetal examination, Visceral, Fresh soft tissue. Fixed tissue. Microdissection... 

Although there are issues around the use of MRI, chiefly the large capital investment required to purchase and run these machines, where the required machines are already available there are clearly scientiflc and logistical advantages for incorporating this technique into routine EFD fetal examination regimes. 

The technical personnel already had extensive experience of fetal examinations in rats and rabbits, but extensive training in the identification of malformations in Xenopus laevis larvae was necessary. Training was a major requirement highlighted by the expert panel to reduce variability. 

Fetal examinations Each fetus (live or dead) sexed, weighed,... 

Fetal examinations Each live fetus weighed and examined for external abnormalities Live fetuses killed and a midcoronal slice made in the head of each fetus to evaluate the contents of the cranium Internal organs of the thoracic and abdominal cavities of all fetuses examined in the fresh state using Staples s technique, and the sex of each fetus determined Viscera removed and discarded Carcasses processed for skeletal examination using the Alizarin Red S staining method and evaluated Findings judged to be variations or malformations... 

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