Establishment of the prediction table of parturition day with ultrasonography in small pet dogs

Establishment of a new equation to estimate gestational age in female dogs

The objectives of this study were to propose a statistical model to predict the behaviour of the thickness of the uteroplacental junction as a function of the gestation period in female dogs and to determine the relationship between the thickness of the placenta and gestational age in healthy female dogs whose pregnancies had elapsed without maternal-fetal alterations. Eight Border Collie female dogs were selected, aged 3-6 (4.48 ± 0.89) and weighing 16-22 kg (19.06 ± 1.9 kg). Female dogs with gestational ages from 20 to 62 days were examined weekly using B-mode ultrasonography. Ultrasound measurements of the uteroplacental junction were organized into four distinct groups: GT1 (27-36 days of gestation), GT2 (37-46 days of gestation), GT3 (47-56 days of gestation) and GT4 (57-62 days of gestation). Based on multiple linear regression, a statistical model was proposed to predict the behaviour of the thickness of the uteroplacental junction (y) as a function of the length of gestation (x) in female dogs, where b0 is the intercept (linear coefficient) and bp is the slope of the predictors. The analysis relating GT, age and weight could predict placental thickness and resulted in a statistically significant model [F(1,28) = 153,736; p < .001; R2  = .846], but only that relating the length of pregnancy (β = .92; t = 12.399; p < .001) predicted the thickness of the placenta according to the equation y = b0 + bp.x1 [(thickness in cm) = β -0.3 + 0.019 × (gestation time in days)]. Only in GT4 was there no correlation between placentas within the same pregnancy (p > .05). Based on the close relationship between the development of the uteroplacental junction thickness during pregnancy and gestational age, it is possible to develop a new tool to complement gestational ultrasound evaluation in female dogs. This is important because it allows better placental evaluation in the search for significant alterations that could compromise maternal-fetal health.

Ultrasonography for the evaluation of pregnancy in the female canine

Ultrasonography can be used for canine pregnancy diagnosis, determination of gestational age, assessing foetal maturation and readiness for birth, monitoring high-risk pregnancies, assessing foetal distress, evaluating bitches in dystocia and foetal gender determination. As the quality and resolution of ultrasound machines have improved, the clinician's abilities to utilize ultrasound as an integral part of reproductive evaluation of all aspects of pregnancy have exponentially increased. This paper reviews the use of ultrasonography throughout pregnancy and the advances made in the interpretation of captured images.

Comparison of two-dimensional (2D) and three-dimensional (3D) ultrasonography for gestational ageing in the early to mid-pregnant bitch

Accuracy of prediction of the day of parturition in the bitch decreases with advancing pregnancy. We hypothesized that three‐dimensional (3D) volume ultrasonography may be superior for gestational ageing than 2D measurements. Thirty‐two pregnancy examinations were performed in 25 bitches of different breeds 21–34 days after the first mating. Ovulation date from serum progesterone concentrations was estimated for 15 bitches, and parturition date was recorded for all dogs. Inner chorionic cavity (ICC) diameters and ICC length of the conceptus were measured by 2D B‐mode, and ICC volume by 3D ultrasonography (Voluson^® i, GE Healthcare). Linear or exponential regressions between ICC measurements and time, i.e. days after estimated ovulation or days before parturition, were performed with significance set at p < .05. ICC volume increased exponentially over time, while ICC diameter showed a linear growth. ICC volume had similar accuracy (R² = .718, p < .001) to ICC diameter and ICC length (R² = .707 and R² = .728, p < .001) when analysed in relation to days after estimated ovulation or in relation to days before parturition (R² = .818, R² = .800 and R² = .810, p < .001 respectively). There were strong (R² ≥ .875) significant associations between all ICC measurements. In conclusion, ICC volume did not improve canine gestational ageing accuracy, which supports the continued use of the ICC diameter, particularly in light of the difficulty in obtaining 3D measurements. On the basis of ICC volume, the growth of the canine conceptus appeared to be exponential already during the first half of pregnancy.

Usefulness of Maternal and Fetal Parameters for the Prediction of Parturition Date in Dogs

An accurate parturition timing is of key importance for breeders and veterinarians in order to give professional assistance to parturition in dogs. However, pregnancy length calculated from the breeding date has a wide variability. Different parameters and formulas have been described and calculated, as well as their accuracy which is affected by various factors: stage of pregnancy, litter and maternal size. Therefore, the selection of the most appropriate parameter panel poses the challenge of weighing their influences and impact on the overall accuracy. The aim of this review is to analyze the parameters useful for parturition timing, especially their accuracy, and to propose the addition of fetal maturity and criteria for its evaluation to detect readiness for parturition. Parameters, as described in literature, are classified as: (i) maternal parameters, (ii) fetal parameters, (iii) ultrasonographic assessment of maternal and fetal heart rate and blood flow, (iv) parameters indicating fetal maturity. A focus on recently described parameters-such as fetal gastrointestinal motility and fetal lung development detected by quantitative ultrasound-is reported. Currently, the most accurate way to predict parturition day is represented by a prepartum progesterone drop, but the identification of a panel of ultrasonographic parameters combining their significance and their accuracy throughout pregnancy is still needed.

Estimated date of delivery in Chihuahua breed bitches, based on embryo-fetal biometry, assessed by ultrasonography

Due to the peculiarities of the reproductive cycle of the female dog, which makes it difficult to accurately ascertain the date of conception, it may be challenging to precisely estimate the gestational age in bitches. Using fetal measurements obtained by ultrasound, it is possible to estimate the gestational age in dogs; however, due to the differences in size of the various breeds, such estimates may have a significant standard deviation, which represents less accuracy when specifying the date of birth. The purpose of this study was to evaluate pregnant female Chihuahuas, establishing relations between the fetal dimensions measured by ultrasound and the remaining time until delivery. Using 13 pregnant female Chihuahuas, weekly ultrasound assessments and measurements were performed, of the inner chorionic cavity, cranial-caudal length, biparietal diameter, abdominal diameter and thoracic diameter. Such parameters were retroactively correlated to the date of delivery, and linear regressions were established between the gestational measurements and remaining days until delivery. The fetal measurement presenting the highest correlation (r = 0.99; P<0.0001) and reliability (R² = 0.98, P<0.0001) with the probable date of delivery was the biparietal diameter, a measurement that can be easily and safely obtained and, when applying a specific formula (Y = -15.46X1 + 38.72), can accurately predict the date of delivery in Chihuahua female dogs.

Estruturas fetais e suas correlações com a predição do dia antes do parto em raças de cães miniaturas

RESUMO Avaliou-se a correlação entre estruturas fetais e extrafetais com a predição do dia antes do parto (DAP) em raças de cães miniaturas. Para isso, realizou-se um experimento, utilizando-se 12 cadelas, com peso corporal entre 3,0kg e 5,0kg, sendo seis da raça Chihuahua, duas da raça Shih-Tzu, duas da raça Spitz Alemão e duas da raça Yorkshire. Foram mensurados, por meio da ultrassonografia, diâmetro biparietal (DBP), diâmetro torácico (DTX), diâmetro abdominal (DAB), comprimento craniocaudal (CCC), diâmetro da cavidade coriônica interna (DCI) e espessura da placenta (EP), a partir do 15º dia após a última monta. Foram estudadas as correlações simples e a significância dos coeficientes de regressão linear simples e o coeficiente de determinação (R), com nível de significância estabelecido em P<0,05. Entre os parâmetros avaliados, DBP, DTX, DAB e CCC foram os mais correlacionados com tempo gestacional, podendo ser utilizados para prever dia antes do parto em cadelas de raças miniaturas.

Genome-wide association analysis uncovers variants for reproductive variation across dog breeds and links to domestication

BACKGROUND AND OBJECTIVES

The diversity of eutherian reproductive strategies has led to variation in many traits, such as number of offspring, age of reproductive maturity and gestation length. While reproductive trait variation has been extensively investigated and is well established in mammals, the genetic loci contributing to this variation remain largely unknown. The domestic dog, Canis lupus familiaris is a powerful model for studies of the genetics of inherited disease due to its unique history of domestication. To gain insight into the genetic basis of reproductive traits across domestic dog breeds, we collected phenotypic data for four traits, cesarean section rate, litter size, stillbirth rate and gestation length, from primary literature and breeders' handbooks.

METHODOLOGY

By matching our phenotypic data to genomic data from the Cornell Veterinary Biobank, we performed genome-wide association analyses for these four reproductive traits, using body mass and kinship among breeds as covariates.

RESULTS

We identified 12 genome-wide significant associations between these traits and genetic loci, including variants near CACNA2D3 with gestation length, MSRB3 and MSANTD1 with litter size, SMOC2 with cesarean section rate and UFM1 with stillbirth rate. A few of these loci, such as CACNA2D3 and MSRB3, have been previously implicated in human reproductive pathologies, whereas others have been associated with domestication-related traits, including brachycephaly (SMOC2) and coat curl (KRT71).

CONCLUSIONS AND IMPLICATIONS

We hypothesize that the artificial selection that gave rise to dog breeds also influenced the observed variation in their reproductive traits. Overall, our work establishes the domestic dog as a system for studying the genetics of reproductive biology and disease.

LAY SUMMARY

The genetic contributors to variation in mammalian reproductive traits remain largely unknown. We took advantage of the domestic dog, a powerful model system, to test for associations between genome-wide variants and four reproductive traits (cesarean section rate, litter size, stillbirth rate and gestation length) that vary extensively across breeds. We identified associations at a dozen loci, including ones previously associated with domestication-related traits, suggesting that selection on dog breeds also influenced their reproductive traits.

Development of specific fetometric formulas of ICC and BP for predicting the parturition date in Maine Coon queens

The objective of study was to derive specific growth curves of ICC and BP for Maine Coon. Twenty-three pregnant queens aged 1-6 years, with body weight of 4.5-7.6 kg, were included in the study. In each queen, serial ultrasonographic examinations of pregnancy were performed through the abdomen with the MyLab Gold Vet scanner with a 6.6-7.5 MHz microconvex probe (Turin, Italy). ICC or BP was measured, depending on the stage of pregnancy. Each examination was regarded as a separate observation. In 18 queens, ICC was measured 33 times, and in 21 queens, BP was measured 60 times. The linear regressions of specific models of ICC and BP in Maine Coon pregnancies and specific formulas for predicting the parturition date in this breed were derived. The ICC formula was: days before parturition (DBP) = -0.79 * mm + 57.9, and the BP formula was: DBP = -1.86 * mm + 49.3. The proposed fetometric formulas of ICC and BP for Maine Coons after application in clinical patients can improve obstetric management in this breed.

Gestational Aging and Determination of Parturition Date in the Bitch and Queen Using Ultrasonography and Radiography

This article provides a complete understanding of how radiography and ultrasound imaging can be used to determine gestational age when inadequate breeding data are available. Formulas for calculation of gestational age using both fetal and extrafetal structures are presented. Ultrasonographic descriptions of organ development and their use in determining gestational age are discussed. This information may be used to monitor the health and development of the fetuses and may be useful when the need to plan an elective or emergency Cesarean section occurs. Ultrasound imaging to assess fetal stress, viability, placental health and to sex fetuses is also described.

Is the biparietal diameter of fetuses in late gestation too variable to predict readiness for cesarean section in dogs?

Correct assessment of readiness for cesarean section is essential for timing elective cesarean section during late pregnancy in the bitch. In humans, biparietal diameter is sufficiently precise and accurate and used in a clinical setting daily. The objectives of this study were to determine whether fetal biparietal diameter in late gestation in the dog could be used to predict readiness for cesarean section by having reached a minimum cut-off value and to correlate the biparietal diameter to birth weight. The biparietal diameter of 208 puppies in 34 litters from 31 English bulldog bitches and 660 puppies in 78 litters from 70 Boerboel bitches were measured immediately after delivery by cesarean section, performed at full term, using digital calipers. At the same time the birth weight of the same 208 English bulldog puppies and 494 of the same Boerboel puppies in 59 litters from 54 bitches was measured by means of an electronic scale. With a cesarean section, all the puppies in a litter are delivered simultaneously and readiness for cesarean section must be determined for a litter. The minimum, median and maximum biparietal diameter varied from 21.1 to 47.8, 32.9 to 50.0 and 34.2-58.2 mm, respectively, among English bulldog litters and from 18.4 to 48.7, 35.5 to 49.7 and 39.8-54.3 mm among Boerboel litters. This large variation suggests that biparietal diameter is too variable within and among litters to be useful as a means of determining readiness for cesarean section.

Specific fetometric formulas of ICC and BP for calculating the parturition date in the miniature breeds of canine

The aim of this study was to derive the growth curves of the inner chorionic cavity and the biparietal distance in miniature dog breeds by ultrasonographic fetometry and present new specific formulas for prediction of parturition date. In this study, foetal biometry parameters were obtained using serial ultrasonographic examinations in 24 pregnant bitches of six different miniature breeds (≤5 kg). The mating time was unknown. Overall, 25 inner chorionic cavity diameter (ICC) and 22 biparietal diameter (BP) measurements were taken. The relationship between ICC or BP growth and days to parturition was analysed by linear regression. The results showed a significant relationship between days before delivery and ICC or BP. The equations derived from the growth curves can be used in practical prediction of parturition date in miniature dog breeds.

The precision of predicting the time of onset of parturition in the bitch using the level of progesterone in plasma during the preparturient period

Precise prediction of the time of onset of parturition in the bitch is of clinical importance. Many parturition management cases in clinical practice are presented in the last two weeks of pregnancy without a reliable estimate of the parturition date. The aim of this study was to assess the value of a single progesterone level in the blood plasma from a preparturient bitch to predict the time of onset of parturition. The temporal relationship between the decrease in the plasma progesterone levels and the time of cervical dilatation (TCD)-which correlates to the onset of stage 1 of parturition-was evaluated in 25 bitches in the preparturient period. Among bitches destined to reach TCD within 12 h there is a 2% probability of having a plasma progesterone level of 15.8 nmoL/L or above and a 6% probability of having a level of 8.7 nmoL/L or above. Conversely, if the level is below 8.7 nmoL/L there is a 99% probability of reaching TCD within 48 h and if the level is below 3.18 nmoL/L there is a 100% probability of reaching TCD within 24 h. These results allow the veterinary obstetrician to make prompt decisions in the management of parturition.

Clinical use of fetal measurements to determine the whelping day in German shepherd breed bitches

The aim of this work was to use a linear regression model previously developed in a pilot study to calculate days before parturition (DbP) using inner chorionic cavity (ICC), biparietal diameter (BPD), crown-rump length (CRL), body diameter (BD) and deep portion of telencephalic vesicle (DPTV) in German shepherd dogs (GSD) with known ovulation day and then to test that model in bitches with unknown ovulation day. In our current study, a model for GSD bitches published in a previous report, proved satisfactory for ICC [DbP=44.76-(4.34×ICC)] and BPD [DbP=38.65-(12.86×BPD)]. We therefore used their model, but developed a new one for CRL, BD and DPTV. For ICC and BPD, we tested accuracy for more than 35days before parturition (ICC) and more than 15days before parturition (BPD). Measurements were taken on at least two fetuses during each ultrasound recording (US) of 22 GSD bitches with known (n=16) and unknown (n=6) ovulation days. The accuracy of the above model was 77-100% for ICC and 83-96% for BPD with a precision of ±1 and ±2days, respectively. Accuracy increased significantly when US was performed more than 35days before parturition for ICC and more than 15days before parturition for BPD. BD and CRL were the most accurate parameters (R²=0.95 and 0.85). In bitches with unknown ovulation day, BD accuracy was 71.4-100% with a precision of ±1day and ±2days, respectively. CRL and DPTV were less accurate (±1day, 60%; ±2days, 80% accuracy).

The Placenta as an Organ and a Source of Stem Cells and Extracellular Matrix: A Review

The placenta is a temporal, dynamic and diverse organ with important immunological features that facilitate embryonic and fetal development and survival, notwithstanding the fact that several aspects of its formation and function closely resemble tumor progression. Placentation in mammals is commonly used to characterize the evolution of species, including insights into human evolution. Although most placentas are discarded after birth, they are a high-yield source for the isolation of stem/progenitor cells and are rich in extracellular matrix (ECM), representing an important resource for regenerative medicine purposes. Interactions among cells, ECM and bioactive molecules regulate tissue and organ generation and comprise the foundation of tissue engineering. In the present article, differences among several mammalian species regarding the placental types and classifications, phenotypes and potency of placenta-derived stem/progenitor cells, placental ECM components and current placental ECM applications were reviewed to highlight their potential clinical and biomedical relevance.

Time of initial detection of fetal structures and anatomic differentiation by using B-mode ultrasound examination 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 (23-25); embryo initial detection at day 22.80 +/- 1.03 (21-24); heartbeat at day 23.0 +/- 0.94 (22-24); yolk sac membrane at day 24.8 +/- 0.78 (24-26); amnionic 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 (33-37); skeleton at day 35.10 +/- 0.73 (34-36).

Estimation of gestational age and assessment of canine fetal maturation using radiology and ultrasonography: a review

Since the duration of pregnancy in the bitch is relatively short, it is critical that fetuses are fully mature prior to delivery for them to survive. For breeders to be able to prepare for normal whelpings and align medical care in case of emergency, an estimated due date is necessary. In cases where ovulation timing is lacking and there is a singleton fetus or oversize fetuses, it is necessary to ascertain gestational age prior to setting the date of Cesarean section. In high-risk pregnancies, where there is poor or no ovulation timing, determination of fetal maturation and gestational age will assist in determining if pregnancy has progressed long enough to allow delivery of viable puppies. In cases where bitches are receiving supplemental progesterone for pregnancy maintenance medications must be discontinued at an appropriate time to permit delivery of viable puppies. It also allows for estimation of the likelihood of fetal survival if the pregnancy is terminated due to failing bitch health, with subsequent surgical delivery of the fetuses. Use of breeding dates alone does not provide due dates with adequate accuracy. In cases where there has been inadequate or no breeding management or ovulation timing, estimation of due date can be performed at the time of pregnancy diagnosis, or closer to term. Radiography can be used to confirm pregnancy and facilitate determination of gestational age, beginning 45d after the LH surge. Ultrasonography can be used from 19 to 21d after the LH surge to term to confirm pregnancy and predict gestational age, and from 25 or 26d to term to assess fetal viability and fetal stress.

Time of initial detection of fetal and extra-fetal structures by ultrasonographic examination in Miniature Schnauzer bitches

Serial ultrasonographic examinations were performed daily on 9 Miniature Schnauzer bitches from the 15th day of gestation until parturition to determine the time the gestational structures were first detected. The gestational age was timed from the day of ovulation (day 0), which was estimated to occur when the plasma progesterone concentration was >4.0 ng/ml. The gestational length in 9 Miniature Schnauzer bitches was found to be 63.0 ± 1.7 (range 61-65) days. The initial detection of the fetal and extra-fetal structures were as follows: gestational sac at day 18.0 ± 0.9 (17-19); zonary placenta in the uterine wall at day 24.9 ± 1.1 (23-26); yolk sac membrane at day 25.0 ± 0.9 (24-26); amnionic membrane at day 27.7 ± 1.0 (26-29); embryo initial detection at day 22.6 ± 0.5 (22-23); heartbeat at day 23.4 ± 0.5 (23-24); fetal movement at day 32.5 ± 0.8 (32-34); stomach at day 31.2 ± 1.6 (29-33); urinary bladder at day 32.6 ± 1.8 (31-35); skeleton at day 34.9 ± 1.6 (34-38) and kidney at day 42.2 ± 0.7 (41-43).

Accuracy of prediction of canine litter size and gestational age with ultrasound

Different sonographic criteria have been developed to estimate canine fetal age, including fetal mensuration and assessment of fetal organ development. This retrospective study assessed the accuracy of gestational age and litter size predictions in 76 bitches using one of two techniques. The first method used the differential features of fetal organ development that occur in early and mid pregnancy, based on published tables for beagles. The second method used biparietal head and trunk diameters to predict gestational age based on tables published for late gestational Labrador Retrievers. The accuracy of the two methods was compared and the effect of maternal body weight and litter size evaluated. Litter size and maternal body weight did not affect the accuracy of gestational age prediction. Using a combination of both methods, the overall accuracy of predicting parturition date within 65 +/- 1 day and +/- 2 days was 70.8% and 86.1%, respectively. The correct litter size was predicted in 65% of cases, and in 89.5% of cases for +/- 1 pup. Pearson's correlation between actual litter size and predicted litter size was high (R = 0.957, P < 0.001). The organ development method of predicting gestational age was more accurate than late gestational fetal mensuration (P = 0.019). The optimum time for sonographic estimation of fetal age and litter size is early and mid pregnancy.

Comparison of the accuracy of two ultrasonographic measurements in predicting the parturition date in the bitch

OBJECTIVES

To compare the accuracy of two ultrasonographic measurements, inner chorionic cavity diameter and biparietal diameter, for the prediction of parturition date in small and medium size bitches. The effects of litter size and fetal sex ratio on the accuracy of the prediction were also investigated.

METHODS

Ultrasonographic examinations were performed on pregnant bitches and, depending on the stage of pregnancy, the inner chorionic cavity diameter and biparietal diameter were measured. The mean value of the data of each structure was calculated and the predicted day of parturition was obtained by the application of equations derived from growth curves we previously developed for different size bitches.

RESULTS

The parturition term was predicted with similar accuracy during early gestation, by the measurement of inner chorionic cavity diameter, as well as during late gestation, by the measurement of biparietal diameter. Litter size affected only biparietal diameter accuracy, whereas fetal sex ratio did not influence the estimation of the day of parturition.

CLINICAL SIGNIFICANCE

Inner chorionic cavity diameter and biparietal diameter were equally reliable parameters in obtaining a reasonably accurate prediction of parturition date at any gestational period at which a bitch is examined.

The Prediction of Parturition Date in Canine Pregnancy

In bitches, the length of gestation is highly variable when measured from the day of mating, thus prediction of parturition may be greatly inaccurate when determined from this point. The ability to precisely predict the duration of pregnancy is of practical importance for managing parturition or planning caesarean section and this review analyses the methods that can be used to accurately forecast the day of parturition. At the time of breeding, determination of the luteinizing hormone surge and the initial rise in progesterone provide reliable information on gestational length of the bitch, but when pregnancy is ascertained, ultrasonography is the most useful tool to predict the delivery day. In fact, by ultrasonographic measurements of the extra-foetal and foetal structures an accurate prediction can be made both in early and late pregnancy.