Ultrasonographic Apperance of the Gestational Structures Throughout Pregnancy in Bitches

Ultrasonographic examinations of 10 pregnant bitches with known breeding dates were made on successive days to establish the identifiable characteristics of pregnancy. Subsequent serial examinations were made to sonographically characterize normal canine prenatal development based about the first mating. The initial detection of the fetal and extra-fetal structures were as follows: gestational sac at day 17.88±1.13 (16-21); zonary placenta in the uterine wall at day 23.70±0.78 (2325); embryo initial detection at day 22.80±1.03 (21-24); heartbeat at day 23.0±094 (22-24); yolk sac membrane at day 24.8±0.78 (24-26); amniotic membrane at day 26.81±0.60 (26-28); fetal movement at day 30.40±1.64 (28-32); stomach at day 33.40±1.07 (32-35); urinary bladder at day 34.90±1.19 (3337); skeleton at day 35.10±073 (34-36).


INTRODUCTION
The early determination of pregnancy and the gestational age are important for reproductive management in small animal practices. In addition, predicting the parturition date can help in managing parturition or planning a Cesarean section in pregnant bitches with multiple mating or an unknown mating time [7] . Ultrasonography is a useful imaging modality for determining pregnancy [4,5,8,15] , estimating the litter size [5,8] , fetal development [9,13] and uterine examination after parturition [2] , a reproductive examination and the direct detection of ovulation [12] . In veterinary medicine, estimation of the gestational age based on the anatomic appearance and predicting the parturition date by an ultrasonographic examination has been reported [1,7,13] . The aim of this study was to make an early determination of pregnancy, to establish the time for the initial detection of the extra-fetal and fetal structures using Ultrasonography and to provide the basic data for estimating the gestational age in bitches.

MATERIALS AND METHODS
Experimental animals: Ten bitches aged 2-4 years old, weighing 17-30 kg housed in surgery and imaging service, Batna University; all bitches were clinically healthy, without history of previous gynecological diseases. The pregnancy was detected using a transabdominal echography performed 15 days after the first mating with a SIEMENS Sonoline adara, Germen equipment and convex 5 MHz transducer. The pregnancy was detected after visualization of gestation sacs and embryos and detection of cardiac function. Each dog was examined twice daily for any swelling of the vulva and the presence of a vaginal discharge, which signified the onset of proestrus. The bitches were mated if these signs were present. Serial ultrasonographic examinations were performed to make an early diagnosis of pregnancy and determine the time of the initial detection of the extra-fetal and fetal structures.
Ultrasonographic examination: Serial ultrasonographic examinations were performed every tow days from day 15 post mating. All the dogs were examined using realtime B-mode ultrasonography in dorsal recumbency. The gestational age at the time of the initial detection and the appearance of the following features of pregnancy were recorded: gestational sac, zonary placenta, feta membrane, embryo, heartbeat, limb buds, skeleton, fetal movement and abdominal viscera.

RESULTS
The Ultrasonography performed between 16 and 21 days after the first copulation, detected pregnancy in all bitches. During this period the uterine vesicle (gestation sac) appearance: a spherical anechoic cavity.
At this stage the embryo is no visible. The ultrasound monitoring of the embryo could be followed as from 22 days post mating.
The time of initial detection of extra-fetal structures: Table 1 and Fig. 1 show the time of the initial detection and presence of extra-fetal structures and Table 2 and Fig. 2 show the time of the initial detection and presence of fetal structures.

DISCUSSION
In this present experiment study the detection of pregnancy in bitches observed an 16 and 21 days after the first copulation. Concannon et al. [3] and Yeager [14] , indicate that the initial diagnosis of pregnancies bitches is possible at 19-20 days after the LH surge, also specify that this result is a discovery uterine vesicle between 13-21 days after the first mating, this study according the observations of Aissi et al. [1] on pregnancies bitches of various breeds in consultation submitted by the owner, a diagnosis of pregnancy is positive after 16 days of the first mating.
The uterine wall surrounding the gestational sac, an apparently hyperechoic inner layer was differentiated to the zonary placenta on day 23.70±0.78 (23-25), which is similar to day 24-28 after ovulation [11] and day 27-30 after the preovulatory LH surge [14] . The embryo and the heartbeat were first detected on day 22.80±1.03 (21-24) and day 23.0±094 (22-24), respectively. Days 21 to 26 and days 21 to 27 were characterized by the finding of an embryo and heartbeat, respectively [6,11,10,14] . Yeager et al. [14] reported little anatomic differentiation within the embryo before day 30. Before day 30, the only distinguishable features of the bipolar embryo were the flickering motion of the heartbeat. In this study, embryo, heartbeat and limb bud were first detected before day 30 post mating.
Most fetal anatomic structures were detected between days 30-50 [14] . At this time, there was a similar time when the fetal structures were first detected (fetal movement, skeleton, stomach, urinary bladder) in the present and other studies [6,11,10,14] . For these reasons, the time the extra-fetal and fetal structures are first detected is useful for estimating the gestational age [1,2] .

CONCLUSION
The aim of this study was to make an early determination of pregnancy, to establish the time for the initial detection of fetal structures and anatomy development using ultrasonography and to provide the basic data for estimating the gestational age in bitches.