As both a veterinarian and a breeder mentor working with thousands of dog breeders around the world through my Elite Breeder Formula program, one of the most common — and heartbreaking — questions I’m asked is:

“Meg, why did my bitch resorb her puppies?”

Fetal resorption is more common than most breeders realise. It happens when an embryo or early fetus dies before the bones have mineralised (usually before about day 35 of gestation). Because the bones aren’t yet calcified, the body simply reabsorbs the tissue — often without any outward sign that anything was ever wrong.

Over the years, I’ve seen countless breeders stress that they “did something wrong,” when in reality many cases are natural biological safeguards that prevent non-viable embryos from continuing to grow. Still, there are identifiable causes, and understanding them means you can truly stack the odds in your favour for future litters.

Below are the key reasons bitches resorb their puppies, based on veterinary science and the real-world breeding data I analyse every day.

1. Embryonic or Genetic Abnormalities (Most Common)

The number one cause of resorption — by far — is embryos that were never viable to begin with.

These occur because of:

• random chromosomal errors

• recessive gene combinations

• inbreeding depression/high COI

• structural genetic defects that are incompatible with life

In these cases the bitch’s body is actually doing the wise thing: stopping development early so she can invest resources into the remaining viable embryos.

2. Hormonal Instability

Progesterone is the hormone that maintains pregnancy. If it dips — even briefly — embryos can be lost.

Possible causes:

• luteal insufficiency (progesterone too low)

• hypothyroidism

• ovarian cysts

• split or irregular cycles

• age-related hormonal decline

If I’m working with a breeder whose bitch repeatedly loses pregnancies at the same early stage, progesterone monitoring is one of the first tools I implement.

3. Infection (Often Subclinical)

I can’t emphasise this enough: a bitch does NOT have to look sick for an infection to cause resorption.

Key culprits include:

• Brucella canis

• E. coli

• Streptococcus canis

• Mycoplasma/Ureaplasma

• Canine herpesvirus (CHV-1)

• protozoal infections like Neospora or Toxoplasma

Herpesvirus is a particularly common contributor and can quietly cause early embryonic death, especially in bitches with a history of small litters or missed pregnancies.

4. Uterine Environment Problems

If the uterus isn’t a healthy place for implantation and placental development, embryos simply don’t thrive.

Contributors include:

• cystic endometrial hyperplasia (CEH)

• scarring from past pyometra

• chronic progesterone exposure

• previous infections

• anatomical abnormalities

This is why I encourage breeders to retire bitches before their uterus has been “cooked” by too many heat cycles.

5. Maternal Health & Stress

Health and environmental stability matter more than breeders often realise.

Factors include:

• obesity (huge factor — increased inflammation disrupts implantation)

• fever or systemic illness around implantation

• high stress (travel, boarding, household disruptors, dog fights, pack instability)

• medications such as corticosteroids

• toxic exposures

Even something as simple as a move to a new home during the first three weeks can raise stress hormones enough to cause losses in sensitive bitches.

6. Sire Factors

Many breeders overlook the male, but poor semen quality and defects in sperm DNA are proven causes of early embryonic loss.

If several bitches bred to the same stud fail to hold pregnancies, I immediately suspect:

• sperm morphology issues

• semen contamination

• genetic incompatibility

• infections transmitted via semen

This is why high-value studs should have regular semen evaluations, not just genetic testing.

When Should Breeders Investigate Further?

I recommend deeper investigation when:

• litter sizes drop over time

• pregnancies vanish between day 25 and day 35

• multiple bitches on the property lose litters

• the same sire is involved in repeated failures

• the bitch is overweight or hormonally irregular

These patterns almost always point to a preventable cause.

What I Suggest as a Step-By-Step Diagnostic Approach

When mentoring breeders, I walk them through this sequence:

1. Confirm pregnancy early (so you know whether resorption actually occurred)

2. Screen for infection

   • vaginal/uterine culture

   • CHV-1 titre

   • Brucella test

3. Assess hormones

   • progesterone checks during early pregnancy

   • full thyroid panel

4. Evaluate uterus

   • ultrasound for CEH or scarring

5. Assess genetics & COI

6. Review health, stress, environment & medications

Following this framework dramatically increases litter retention.

In A Nutshell

Bitches resorb puppies because something disrupted early embryonic development — most commonly genetics, hormones, infection, or uterine health. As breeders, our job is to create the conditions where as many embryos as possible can implant, thrive, and develop into healthy puppies.

Helping breeders achieve this is one of the core pillars of what I teach inside the Elite Breeder Formula program — because once you understand why these losses happen, you gain the power to prevent the majority of them.