Canine Pregnancy Study Guide

Overview and Clinical Importance

Canine pregnancy management is a critical area of small animal theriogenology that encompasses accurate pregnancy diagnosis, recognition and management of gestational complications, and understanding the normal parturition process. Normal canine gestation is 64-66 days from the LH surge (or 56-58 days from first day of diestrus), though this can appear variable (58-72 days) when calculated from breeding dates due to the prolonged viability of canine sperm in the reproductive tract.

The NAVLE frequently tests candidates on pregnancy diagnosis methods, fetal viability assessment, recognition of dystocia, and appropriate interventions. Understanding the timing and indications for each diagnostic modality, as well as the criteria for medical versus surgical management of complications, is essential for examination success and clinical practice.

Section 1: Pregnancy Diagnosis Methods

Multiple diagnostic modalities are available for confirming canine pregnancy. The choice of method depends on the stage of gestation, the clinical question being asked, and the information required.

Pregnancy Diagnosis Methods Comparison

Ultrasonographic Pregnancy Diagnosis

Ultrasonography is the gold standard for early pregnancy diagnosis and fetal viability assessment. Key landmarks include: gestational sacs visible from Day 20 as anechoic circular structures, embryo proper visible by Day 23-25, and fetal heartbeat detectable by Day 25. The zonary placenta becomes distinguishable around Day 24-28.

Ultrasonographic Landmarks by Gestational Day

Fetal Heart Rate Assessment

Fetal heart rate (FHR) monitoring is critical for assessing fetal viability and distress. Normal canine FHR averages 220-240 bpm. The following thresholds guide clinical decision-making:

Section 2: Pregnancy Complications

Early Embryonic Death and Fetal Resorption

Pregnancy loss before Day 35 typically results in embryonic resorption without external clinical signs. The bitch may appear to have "failed to conceive" rather than having lost a pregnancy. Up to 43% of canine pregnancies may experience some degree of fetal resorption. After Day 35-40, fetal death leads to abortion, mummification, or maceration.

Causes of Pregnancy Loss

Eclampsia (Puerperal Hypocalcemia)

Eclampsia is an acute, life-threatening hypocalcemia occurring most commonly 1-4 weeks postpartum during peak lactation, but can occur during late pregnancy or parturition. Small breed dogs nursing large litters are at highest risk.

Section 3: Normal Parturition (Whelping)

Predicting Parturition

Accurately predicting whelping date is critical for monitoring and intervention. The most reliable methods include: Progesterone monitoring (parturition occurs within 24 hours of progesterone dropping below 2 ng/mL), and temperature monitoring (rectal temperature drops below 99°F/37.2°C approximately 8-24 hours before whelping).

Stages of Labor

Stage I: Cervical Dilation (Duration: 6-24 hours)

Characterized by uterine contractions (not visible externally), cervical dilation, and behavioral changes. Clinical signs include:

• Restlessness, nesting behavior, reclusive attitude
• Panting, trembling, inappetence, possible vomiting
• Clear, mucoid vaginal discharge
• Temperature drop to less than 99°F (37.2°C) - may last only 8 hours

Stage II: Fetal Expulsion (Duration: 3-12 hours total)

Marked by visible abdominal contractions and delivery of puppies. Both cranial (60%) and caudal (40%) presentations are NORMAL in dogs - only transverse presentation is abnormal.

• Active straining with visible abdominal efforts
• Each puppy delivered within 10-60 minutes of active straining
• Interval between puppies: 30 minutes to 4 hours (up to 4 hours acceptable with no active labor)
• Bitch should remove fetal membranes and stimulate breathing

Stage III: Placental Expulsion

Occurs simultaneously with Stage II as bitches alternate between delivering puppies and placentas. Each placenta is typically expelled 5-15 minutes after its associated puppy. Count placentas - retained placentas can cause metritis.

Section 4: Dystocia

Dystocia (difficult birth) occurs in approximately 5-6% of all canine pregnancies, but is much higher in certain breeds - approaching 100% in English Bulldogs. Uterine inertia is the most common cause (approximately 60% of cases), followed by fetal causes.

Criteria for Diagnosing Dystocia

Intervene immediately if ANY of the following occur:

• Green/black vaginal discharge (lochia) before first puppy delivery - indicates placental separation
• Active straining greater than 30 minutes without delivery of a puppy
• Weak/intermittent contractions for greater than 2-4 hours without delivery
• Greater than 4 hours between puppies with no active labor
• Stage II labor exceeding 12 hours total duration
• Fetus visible at vulva or fetal membranes protruding greater than 15 minutes
• Dam showing signs of systemic illness, exhaustion, or collapse

Causes of Dystocia

High-Risk Breeds for Dystocia

Brachycephalic breeds (English Bulldog, French Bulldog, Boston Terrier, Pug) have the highest risk - over 80% of English Bulldogs require cesarean section due to fetal-pelvic disproportion. Other high-risk groups include: toy breeds, Scottish Terriers, and breeds with dolichocephalic heads (Collies, Shetland Sheepdogs).

Dystocia Management

Medical Management

Only appropriate when: No obstruction present, cervix dilated, normal fetal size and position, fetal heart rate greater than 180 bpm, dam systemically stable.

Surgical Management: Cesarean Section

Indications for immediate cesarean section:

• Fetal heart rate persistently less than 180 bpm
• Obstructive dystocia (fetal-pelvic disproportion, fetal malpresentation)
• Failure to respond to 2-3 doses of oxytocin
• Maternal systemic compromise
• Prolonged dystocia (greater than 4.5-6 hours increases stillbirth rate)
• Uterine torsion or rupture