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Fırat Üniversitesi Sağlık Bilimleri Veteriner Dergisi
2016, Cilt 30, Sayı 2, Sayfa(lar) 089-093
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Tavşanlarda Gebelik Boyunca B-mod ve Doppler Ultrasonografi Yardımıyla Fötal Gelişimin Incelenmesi
Berkay TURNA, Güneş ERDOĞAN
Adnan Menderes Üniversitesi, Veteriner Fakültesi, Doğum ve Jinekoloji Anabilim Dalı, Aydın, TÜRKİYE
Anahtar Kelimeler: Fötal gelişim, umblikal arter, doppler indeksi, tavşan
Özet
Tavşanlarda gebelik boyunca fötal biometrik parametreler ve umbilikal arter kan akımına ait Doppler parametreleri incelendi. On adet sağlıklı Yeni Zelanda ırkı dişi tavşan kullanıldı. Gebeliğin 9-30 günleri arasında 3-4 gün aralıkla B-mod ve Doppler ultrasonografik muayeneler yapıldı. Sol kornunun en kaudalindeki fetüs üzerinde baş sağrı uzunluğu (BSU), biparietal baş çapı (BPÇ), göğüs çapı (GÇ) değerleri kaydedildi. Ek olarak, a. umbilikalis üzerinden fetal kalp atım sayısı (FKAS), pulsatil (PI) ve resistans (RI) indeks ölçümleri kaydedildi. Biometrik parametreler arasında BSU değeri gebelik yaşı ile yüksek korelasyonu gösterdi (r= 0.981). Yine BSU ve GÇ değerleri ile gebelik yaşı arasında yüksek pozitif korelasyon kaydedildi (r= 0.971). Fetal kalp atım sayısı, PI ve RI değerlerinin gebelik yaşı ile daha düşük negatif korelasyon gösterdiği (r= -562), (r= -0.383), (r=-0.730) tespit edildi. Gebeliğin 20. gününden sonra PI sabit kalırken, RI ise belirgin şekilde düşüş gösterdi (P<0.01) ve sonrasında doğuma kadar stabil kaldı. Bu çalışma sayesinde fetal gelişimin değerlendirilmesi ve monitorizasyonunda kullanılabilecek yeni veriler sağlanmıştır. Tavşan gebeliklerinde 20. günün umbilikal arter indeksleri açısından eşik noktası olabileceği düşünülmektedir.
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    Use of rabbits in human reproductive studies has been increasing particularly about reproduction in the last decades1-4. They are considered as an ideal animal model because of similarity to that of human maternal-fetal units and, also because its size is suitable for using conventional veterinary scanners5. Although there are several studies on sonographic results of rabbit pregnancy6-8, the conclusive results of the monitoring fetal growth via ultrasound6,9,10 are limited.

    Beside B-mode ultrasonography, obstetric Doppler applications have been used in different species for monitoring fetal well-being noninvasively11-13. By recording of the pulsatility and resistance in the fetal-maternal vessels, the hemodynamic parameters that have an important clinical implication for fetal surveillance can be obtained. Some specific changes in uteroplasental and fetal arteries related to intrauterine growth restriction (IUGR) are clearly recorded in the rabbit models4,14,15. These studies mainly carried on as an experimental study for human medicine. But Doppler examinations in fetal assessment have not been routinely used in clinical work in the veterinary practice on rabbits. However, it was a well known risk that after palpation of rabbits in pregnancy diagnosis, maternal and also fetal health may deteriorate.

    In the current study, it was aimed to evaluate the fetal somatic growth and umbilical artery Doppler indices in healthy pregnant rabbits. In other words, the objective was to assess the relationships between fetal biometric/Doppler parameters and gestational age, after then to describe the changes of umbilical artery Doppler indices in the healthy pregnancies in order to establish a database for fetal monitoring in rabbit pregnancy.

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    Animals: In the present study, 10 healthy, sexually mature New-Zealand white female does weighing 3.6 - 4.1 kg were used. The does were housed individually in wire mesh cages under controlled light (14h light: 10h dark) and temperature (18 to 24 °C) conditions. All does were with free access to water and standard pellets. Animal handling and all procedures were performed in accordance with regulations and guidelines and with the approval of the Animal Experimental Ethics Committee of the Adnan Menderes University (050.04/2011/011). Before the start of the experiments, the does were accustomed to the environment and trained to medical manipulations for three weeks. Females were mated with sexually active bucks of the same strain and the day of controlled mating, was considered Day 0 of the pregnancy.

    Pregnancy Diagnosis, and B-mod and Doppler Ultrasonographic Examinations: At 7-9th day postmate, pregnancy diagnosis was confirmed by ultrasonographical examination (MyLab 30-Esaote@, Genova, Italy) using a micro-convex probe of 8 MHz. B-mode and Doppler ultrasonographic exams were performed at 3-4 days intervals (9-13-16-20-23-27 and 30th day) throughout pregnancy. Prior to the examination, the abdominal ventral region of each doe was shaved. They were not sedated during the study. The transducer was covered with a copious amount of gel to eliminate air spaces. The measurements of CRL, BPD, TD were recorded from the most caudal of fetus, positioned in the left uterus horn. Following the biometric measurements, umbilical artery blood flow waveforms were obtained from the midcord site of the free floating umbilical cord.

    Following the visualization of the umbilical artery using color Doppler; Pulsed-wave Doppler examinations were performed. Records were obtained regularly for at least three consecutive arterial waveforms. Waveforms were disregarded during fetal and maternal movements or cardiac arrhythmias. In order to evaluate the blood flow waveform patterns of the umbilical artery, the FHR, PI and RI were measured. Due to the possible thermal and cavity side effects of Doppler sound waves on tissues, Pulsed-wave examinations did not exceed 30 seconds and were recessed for 1 minute. Regarding to stress factors of the study group, all examinations were performed between 9:00-12:00 AM and 50-60 minutes totally in silent and dimly lit room, and were performed by the same trained operator.

    Data Analysis and Statistics: Average data presented as mean ± SEM. Means were compared using a paired Student's t-test and x² test (Minitab-16) when appropriate. Regression models were fitted to evaluate the relationship between the day of pregnancy and biometric / doppler parameters which were considered to be dependent on the day of pregnancy. A 5% significance level was used.

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    Animals: In all does, ultrasonographic examinations have accurately predicted pregnancies with no false negatives or positives. During pregnancy, no maternal disorder and fetal loss finding was recorded. Moreover, no trace having pathological Doppler findings suggestive of fetal stress (end diastolic block and /or notch formation e.g.) was recorded during the study. The does tolerated the ultrasonographic examinations well. Parturitions were observed 28±0.5 d (SEM) after mating normally without any sign of stress. The does gave birth to 8±0.5 live pups without assistance. There were no stillbirths or new-born deaths after delivery.

    Biometric Parameters: Figure 1 presents the mean values of BPD and TD of fetuses during pregnancy in rabbits. BPD values were the most correlated with the gestational age (r=0.981; P<0.001) and were able to measurable in second and third trimester practically. TD values were high positive correlation with the gestational age (r=0.972; P<0.001). Mean while CRL values were recorded in only second trimester due to due to possibility of fitting on the screen. CRL values were high positive correlation with the gestational age (r=0.972; P<0.001).


    Büyütmek İçin Tıklayın
    Figure 1: The mean BPD and TD values of rabbit fetuses during pregnancy

    Doppler Parameters: The umbilical artery blood flow was characterized low resistance and showed systolic waveform during the second trimester of pregnancy. As of day 20, onward, diastolic waveform could be detected in the Doppler examinations (Figure 2).


    Büyütmek İçin Tıklayın
    Figure 2: The image of Pulsed-Doppler ultrasonography of a. umbilicalis on 20th day of pregnancy

    Figure 3 presents the mean values of FHR in umbilical artery of rabbit fetuses during pregnancy. FHR increased gradually as the pregnancy progressed and the peak values were recorded on day 20 of pregnancy. After then, it decreased following two examinations and increased again after 27th days of pregnancy (P<0.05). It was observed that the FHR negatively correlated with gestational age (r=-0.562; P< 0.001).


    Büyütmek İçin Tıklayın
    Figure 3: The mean FHR of rabbit fetuses during pregnancy

    Figure 4 presents PI and RI of umbilical artery. They were negatively correlated with gestational age (r=-0.383; P<0.01) and (r=-0.730; P<0.001), respectively.


    Büyütmek İçin Tıklayın
    Figure 4: The mean PI and RI indices of umbilical artery of rabbit fetuses during pregnancy

    From day 20 onwards, umbilical artery RI decreased significantly (P<0.01), after then it became stable until parturition. Meanwhile, PI curve has no change significantly (P>0.05) during pregnancy (Figure 4).

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    Although the time between parturition is short, pregnancy diagnosis and estimation of the gestational age should be considered important in rabbit practice. In case of lack of reports of the date of mating, transabdominal ultrasonographic examinations would be used effectively and practically in clinics and farms.

    The rabbit uterus is ultrasonographically detectable only in pregnant animals. Averagely 8 mm-diameter fluid-filled embryonic vesicles are seen as anechoic, round shape formations and uterine wall is getting thicker7. Pregnancy diagnosis was performing apparently at days of 7 postmating by seeing vesicles which diameter 10-12 millimeters5,7,8. In this study, embryonic sacs were detectable on 7th day of pregnancy, according to the results of earlier studies5,9. But the conclusive diagnosis was done based on signs of 9th day postmating again in order to the exaclude possibility of the early embryonic losses. Moreover, it could be possible that the Doppler examinations are performed with a microconvex probe with 8 MHz from this day onward.

    There have been several detailed studies on fetal somatic growth and also fetal Doppler findings in rabbit5,10,16. Concerning of fetal biometric parameters results reported in previous studies, the agreement between our study's results and others were seen. Regarding the high correlations between the day of the pregnancy and the somatic growth parameters, CRL, BPD and TD are seen as very reliable parameters for determining gestational age in cases with an unknown breeding date. In the present study, BPD was measurable throughout pregnancy and has the highest correlation value with gestational age. Therefore, it can say that BPD is the most reliable and practical biometric parameter in assessment of fetal growth in rabbit.

    Fetal heart rates have been extensively analyzed to describe normal development over the course of pregnancy. It is well recognized that FHR decreases along with pregnancy in sheep and goats17,18, and it remains more stable in dogs11 and cats19. But there has been a limited FHR findings in rabbit fetuses. Polisca et al10 observed no significant change in FHR during pregnancy. But in the present study, different FHR curve was recorded. The similar decreasing trend was only observed between 20th and 27th days. In the last examination on 30th day, FHR increased again the prior to parturition. In our opinion, this differences in FHR curve is not attribute to fetal stress related with any pathology due to minimizing of environmental stress factors and also no pathological Doppler findings suggestive of fetal stress (end diastolic block and /or notch formation e.g.) were detected during the study. Therefore, this increase seen in the last days of pregnancy can be related to physiological fetal stress that triggers the parturition process. Another results of Doppler exams revealed that the low success of the estimation of the gestational age based on FHR. In earlier studies, FHR value correlated in a wide range (r= -0.77 and -0.55) with gestational age during pregnancy in Saanen goats18 and Egyptian native goats20. Moreover, there is no data related to these correlations in rabbit fetuses. Therefore FHR, PI and RI values would be inconsistent in rabbit due to low correlations comparing with other biometric parameters.

    Following the evaluation of the Doppler examinations, it is possible to say that the findings of 20th day of pregnancy can be accepted as threshold in this study. The umbilical arterial blood flow that has typically low-resistance was characterized only by systolic waveform until the 20th day. On the 20th day of pregnancy, RI decreased significantly (P<0.01) after then, it was stable until parturition. Although PI value has no change significantly, its curve tended to decrease. According to the previous studies in different species12,21-23, diastolic waveform takes places following the decreasing of Doppler indices. The last third of tfe pregnancy is very important and characterized by maximum fetal growth and rate, therefore, due to the need for a higher amount of nutrient24. In our opinion, the resistance in umbilical vessels started to decrease significantly at this stage and fetal blood flow within the umbilical cord can be seen in diastolic phase continuously. In rabbit IUGR models, fetal growth retardation findings could be seen examinations at day 2115. Consequently, the biometric and Doppler examinations findings should be evaluated together in the antenatal assessment of fetal growth in third trimester.

    In conclusion, ultrasound monitoring with B-mode and Doppler may be a useful tool for assessment of fetal growth in the second and third trimester in the rabbit. BPD should be the first choice for estimation of gestational age and can be used as an important parameter for fetal growth retardation. Although umbilical artery blood flow shows some similarity with other species especially in the last trimester, futher studies should be undertaken to evaluate the feto-maternal hemodynamic changes. The findings herein could be interest to researchers studying the rabbit reproduction and also fetal monitoring and may be used in the future.

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    1) Denton KM, Flower RL, Stevenson KM, et al. Adult rabbit offspring of mothers with secondary hypertension have increased blood pressure. Hypertension 2003; 41: 634-639.

    2) Nesbitt AE, Murphy RJ, O'Hagan KP. Effect of gestational stage on uterine artery blood flow during exercise in rabbits. J Appl Physiol 2005; 99: 2159-2165.

    3) Carter AM. Animal model of human placentation: A review. Placenta 2007; 28:41-47.

    4) Eixarch E, Figueras F, Hernández-Andrade E, et al. An experimental model of fetal growth restriction based on selective ligature of uteroplacental vessels in the pregnant rabbit. Fetal Diagn Ther 2009; 26: 203-211.

    5) Chavatte-Palmer P, Laigre P, Simonoff E, et al. In utero characterisation of fetal growth by ultrasound scanning in the rabbit. Theriogenology 2008; 69: 859-869.

    6) Griffin PC, Bienen L, Gillin CM, et al. Estimating pregnancy rates and litter size in snowshoe hares using ultrasound. Wildlife Soc Bull 2003; 31: 1066-1072.

    7) Ypsilantis P, Saratis P. Early pregnancy diagnosis in the rabbit by real time ultrasonography. World Rabbit Sci 1999; 7: 95-99.

    8) Gutierrez HE, Zamora FMM. Ultrasonography study of rabbits pregnancy. In: Proceedings of the 8th World Rabbit Congress. Puebla, Mexico WRC; 2004: 276-280.

    9) Soroori S, Dehghan MM, Molazem M. Ultrasonographic assessment of gestational age in rabbit. In: Proceedings of the 15th Congress of FAVA. FAVA-OIE Joint Symposium on Emerging Diseases. Bangkok, Thailand 2008: 367-368.

    10) Polisca A, Scoti L, Orlandi R, et al. Doppler evaluation of maternal and fetal vessels during normal gestation in rabbits. Theriogenology 2010; 73: 358-366.

    11) Zone MA, Wanke MM. Diagnosis of canine fetal health by ultrasonography. J Reprod Fertil Suppl 2001; 57: 215-219.

    12) Dubiel M, Breborowicz GH, Gudmundsson S. Evaluation of foetal circulation redistribution in pregnancies with absent or reversed diastolic flow in the umbilical artery. Early Hum Dev 2003; 71: 149-156.

    13) Schwarze A, Nelles I, Kraip M, et al. Doppler ultrasound of the uterine artery in the prediction of severe complications during low-risk pregnancies. Arch Gynecol Obstet 2005; 271: 46-52.

    14) Hodges R, Endo M, La Gerche A, et al. Fetal echocardiography and pulsed-wave Doppler ultrasound in a rabbit model of intrauterine growth restriction. J Vis Exp 2013; 29 e50392: 1-8.

    15) Lopez-Tello J, Barbero A, Gonzales-Bulnes A, et al. Characterization of early changes in fetoplacental hemodynamics in a diet-induced rabbit model of IUGR. J Dev Orig Health Dis 2015; 6: 454-461.

    16) Mourier E, Richard C, Chavatte-Palmer P. Ultrasound monitoring of fetal and placental growth and vascularization in the rabbit. Placenta 2014; 35: 9.

    17) Gunduz MC, Turna O, Ucmak M, et al. Prediction of gestational week in Kivircik ewes using fetal ultrasound measurements. Agri J 2010; 5: 110-115.

    18) Serin G, Gokdal O, Tarimcilar T, et al. Umbilical artery Doppler sonography in Saanen goat fetuses during singleton and multiple pregnancies, Theriogenology 2010; 74: 1082-1087.

    19) Verstegen JP, Silva LD, Onclin K, et al. Echocardiographic study of heart rate in dog and cat fetuses in utero. J Reprod Fertil Suppl 1993; 47: 175-180.

    20) Karen AM, Fattouh El-Sayed M, et al. Estimation of gestational age in Egyptian native goats by ultrasonographic fetometry. Anim Reprod Sci 2009; 114: 167-174.

    21) Nautrup CP. Doppler ultrasonography of canine maternal and fetal arteries during normal gestation. Reprod Fert Develop 1998; 112: 301-314.

    22) Di Salvo P, Bocci F, Zelli R, et al. Doppler evaluation of maternal and foetal vessels during normal gestation in the bitch. Res Vet Sci 2006; 81: 382-388.

    23) Scotti L, DiSalvo P, Bocci F, et al. Doppler evaluation of maternal and foetal vessels during normal gestation in queen. Theriogenology 2008; 69: 1111-1119.

    24) Symonds ME, Clarke L. Nutrition-environment interactions in pregnancy. Nutr Res Rev 1996; 9: 135-148.

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