Why Does It Matter If We Say Due Date or Whelping Window?

Although most breeders understand that due dates are just estimates, several key ideas get lost in this concept. First, most breeders don’t know what is normal variation around a bitch’s due date. Is it okay for pups to be born 4 days early? Is it safe for bitches to be 3 days overdue? Due dates don’t tell us when we need to be concerned and, more importantly, when we need to act.

In addition, many breeders don’t know how a due date is calculated and thus how accurate it is. Do we count from the first breeding, the last breeding, when she came in season, when her progesterone hit 5 ng/ml, or from confirmed ovulation? And does it matter which date we start from? And are different starting points more or less accurate in predicting whelping?

What Are Whelping Windows?

Believe it or not, there are some good research that can help us answer these questions but none of those studies will give us a “due date” for our dogs! Instead, all of the research in pregnant dogs gives ranges of dates, or whelping windows, during which pups can be safely born. More importantly, these ranges tell us when our pups will be:

• premature and thus their chance of survival is quite slim. Veterinarians can treat bitches in premature labor, if they know it is actually premature, and breeders can prepare to take extreme measures to save their premature puppies.
• overdue and must be born quickly if they are to survive. Canine placentas have a limited lifespan, after which they begin to deteriorate rapidly, putting any remaining puppies at risk. Truly overdue bitches usually need c-sections if all of their pups are to survive.

Estimating Whelping Windows

Whelping windows can be estimated from three events, none of which are breeding dates. Instead, we need to one or more of these dates:

• LH surge
• ovulation
• onset of diestrus

When we talk about our whelping windows, we also need to identify the event it is based on. Thus, I might say, “Glee’s whelping window is from December 6-8 based on Day 1 of diestrus.” Of these three events, diestrus is the most accurate in predicting whelping, followed by the LH peak.

The only way to determine the first day of diestrus is through vaginal cytology, which is easily learned and can be done by breeders at home. You’ll need to do swabs for several days in a row to determine when your bitch transitions from estrus to diestrus. Once you know when diestrus started, your bitch’s whelping window is from 56 to 58 days later (England, 2003).

The other two tests–LH and progesterone–require blood draws for clear serum and, in most cases, veterinary and/or lab assistance. You will often need to run multiple tests to accurately identify the LH peak and/or ovulation. Once you have one or both of those dates, you’ll be able to identify a 5-day whelping window. Bitches will normally whelp between 63 and 67 days after the LH peak or 61 to 65 days after ovulation.

Pups born outside of these windows will be either premature or overdue. In dogs, neither of these situations is safe for pups. Premature pups are incompletely developed, especially their lungs. Overdue pups often experience rapid placental deterioration that results in stillborn pups. In both cases, we can take steps to help the pups with the assistance of our veterinarians.

• If a bitch goes into labor before her whelping window opens, it is a medical emergency and you need to get her to a vet ASAP to save the puppies. Puppy development continues right up to the whelping window but there are steps your vet can take to stop labor and/or prepare the pups for birth.
• If a bitch has not gone into labor as her whelping window closes, it is also a medical emergency and you need to get her to a vet ASAP, most likely for a c-section. Canine placentas only last so long and begin to deteriorate rapidly at the end of the whelping window.

In the case of very small or large litters, you can narrow your whelping windows further. Very large litters are likely to arrive early, toward the beginning of the whelping window and small litters are likely to be born toward the end of the whelping window.

The calendar below is an example from one of our litters earlier this year. We pinpointed all three events during our bitch’s season, estimating her whelping window to July 15 through 19. Diestrus narrowed that window further to July 16 through 18. If she had not had her pups by the morning of July 19, we had a c-sectioned planned. Luckily, the pups arrived on July 18.

Yellow: pups are seriously premature and will need labor to be halted or extreme post-whelp measures to survive
Green: whelping windows, normal gestation
Red: pups are overdue and likely to die in utero without immediate assistance

As you can see, whelping windows can vary across the three tests but usually only by a day on either end. To determine your bitch’s whelping window from your results, depend first on diestrus, if you have it. Second, use a positive LH test. If you don’t have either of those, use her ovulation date to determine her 5-day whelping window.

So let’s all start using “whelping window” instead of “due date” so we can better manage our bitches’ pregnancies and have more healthy pups!