Premature Labor in Canines
Copyright 2019 Veterinary Perinatal Specialties. Karen Copley, RNC, BSN
Veterinarians and breeders are experiencing an increasing incidence of mid gestation fetal losses in canine pregnancies. These losses can be either partial losses; multiple puppies are “resorbing” while others appear to be “OK”, as well as complete litter loss. Efforts to manage these compromised pregnancies are frequently ineffective when using un-monitored therapies. As part of our early database, the WhelpWise service began identifying increased uterine activity either as “irritability” or actual uterine contractions that have correlated with these fetal losses as early as 1999. The WhelpWise service utilizes a uterine monitor and sensors specifically designed for veterinary obstetrics to identify uterine activity. Documentation of actual uterine contractions or uterine irritability has been an essential tool in accurate diagnosis and management of premature labor.
Premature labor is defined as the presence of an organized pattern of uterine contractions that are inappropriate for a specific point in gestation (organized contractions occurring earlier than day 58 post LH surge). If premature labor is not managed immediately, premature deliveries will occur. Threatened premature labor is defined as the presence of uterine contractions/uterine irritability that has not resulted in fetal delivery, but uterine activity is abnormal for that specific point in gestation. Un-managed contractions or uterine irritability will frequently progress into premature deliveries. A second risk of premature contractions/uterine irritability is the damage and subsequent placental separation the premature contractions contribute to, causing fetal compromise/demise. Documentation of excessive uterine contractions with the WhelpWise service is essential to both the correct diagnosis and management of preterm labor.
The cause of premature labor is frequently unknown. Using historical evaluation of clients actively managed for premature labor using the WhelpWise™ system, we find three clear categories; idiopathic, hypoluteal, or the presence of infective pathology. It is not unusual for there to be a combination of these causes.
Symptoms of premature labor are frequently not noted until the presence of “uteroverdin” the dark green/black vaginal discharge or actual deliveries of fetuses are noted. It is not unusual for an animal to have an asymptomatic loss of a litter on a first occurrence of preterm labor. If the cause of preterm labor is hypoluteal, the presence of inappetence and nesting behavior may be noted. If the cause is infective, vaginal discharge or excessive vaginal licking may be noted. Specific diagnostic testing is highly recommended before a “diagnosis” is made.
Causes of preterm labor or uterine irritability
- Use of uterotonics during gestation such as Red Raspberry and Caulophyllum.
- Hypolutealism (or “low progesterone”).
- Vaginitis/placentitis/pyometra can all be causative factor for preterm labor. It is important to identify pathogens prior to antibiotic therapy as frequently the causative agent is resistant to common antibiotic therapy. It is also possible to co-manage preterm labor with active infective processes such as pyometra safely with close maternal/fetal assessments.
- Breed predisposition; Cavalier King Charles Spaniel, Miniature Schnauzer, Bouvier, Newfoundlands, and Mastiffs have shown a higher incidence of premature labor.
Hypolutealism or “low progesterone”
Little documentation exists showing the normal progesterone decline throughout gestation. Progesterone levels noted in our normal client base with the WhelpWise system have had a wide range of variation. Some progesterone levels have been very low without concerning uterine activity. It becomes difficult to determine what a specific progesterone level should be for a specific point in gestation as many factors can contribute to each individual level such as breed and litter size. This area of ambiguity can lead the veterinarian to prescribe progesterone based on an inaccurate database of what a progesterone level should be at a certain point in gestation. Alternately a progesterone level could be deemed “just fine” when it may or may not be. The concept that any progesterone greater than 2ng/ml at before 58 days is “OK” and will maintain a pregnancy has not been demonstrated in our WhelpWise population. Progesterone’s primary “job” for gestation is to prevent the uterus from contracting, thus promoting healthy placentas and placental blood exchange. A contracted uterine muscle; whether it is from actual contractions or from uterine irritability will restrict blood flow to the growing fetus and placenta, causing both fetal growth retardation and placental detachment. The best assessment tool for premature labor in cases of suspected hypolutealism is to evaluate “end organ response” by using the WhelpWise service. Regardless of the progesterone level, is progesterone doing its “job” i.e. is the uterus free from contractions or irritability?
Management of Preterm Labor
Once uterine contractions have been identified, management can include a variety of approaches. If hypolutealism is suspected progesterone therapy can begin, with evaluation of an effective progesterone levels being documented by the WhelpWise service, showing uterine quiescence. Hypolutealism can be managed by Regumate, oral human preparations, and injectable oil-based progesterone. By monitoring for a lack of uterine contractions we know that the progesterone level is effective regardless of mode of administration. If therapy is not effective as noted by WhelpWise, alternate routes of administration can be explored. An additional advantage of using WhelpWise to manage a hypoluteal pregnancy is when weaning progesterone. By continuing to monitor contractions the breeder and veterinarian can be assured that uterine activity is not increasing before the expected delivery date. Should uterine activity increase additional medications other than progesterone can be added to maintain a stable uterine environment.
For causes of preterm labor/uterine irritability that are not associated with hypolutealism, medical management of uterine activity with medications such as Terbutaline or Calcium Channel Blockers can control premature contractions, and dosing for those medications can be specifically adjusted to control excessive uterine activity with the WhelpWise service.
When to Start Preterm Labor Monitoring
The most successful management comes with early detection of preterm uterine activity. In cases where a prior preterm delivery has occurred, we suggest starting to monitor 10 days earlier than the prior delivery occurred. In some cases, this may put uterine monitoring earlier than an ultrasound to confirm pregnancy. We have been able to correlate resorptions on a pregnancy confirmation ultrasound to early preterm labor. The earliest in gestation that we have been able to detect preterm labor activity is 14 days post LH surge. Prior history for this bitch had shown premature delivery at 45 days in the first litter, second litter she had lost all the puppies at ultrasound. Monitoring was initiated at 10 days post LH surge with uterine activity being noted at 14 days. The pregnancy was managed with tocolytic therapy (tocolytics are medications that stop contractions) and we successfully got the litter of five puppies to term.
Preterm labor/uterine irritability is impossible to diagnose and manage without the use of the WhelpWise service. In addition to our monitoring equipment you have the added advantage of 20 years of high-risk pregnancy management from our extensive database. Our success rate getting a high-risk litter to term gestation is about 96% for our premature labor clients. WhelpWise has become an important tool for preterm labor management for many successful breeders. In the most extreme cases we have been able to stop bitches that are actively delivering puppies and keep the rest of the litter in until the end of pregnancy.
Early detection of problems greatly increases the chance of successful management. If you think your bitch may have a problem with preterm labor, please contact us immediately upon breeding so we can get her on our schedule. Documentation of excessive uterine contractions with the WhelpWise service is essential to both the correct diagnosis and management of preterm labor.
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