Persistent Pseudo Pregnancies in Dogs

<TL;DR>

• Female dogs are more reactive for 2 months after their season
• When spayed, female dogs can be left in a permanent phantom pregnancy leaving them more anxious and reactive for the rest of their lives – good news, this is easy to treat
• Keep a note of the day the season starts in your diary
• Watch out for behavioural changes within 2 months of a bitch being spayed

</TL;DR>

The average cycle for the average female dog is every 7 months, however the range can vary quite widely.

Progesterone

During the season progesterone is elevated.  Progesterone is the pregnancy hormone.  It starts to rise just before ovulation, peaks at about 20 days after ovulation and returns to baseline approximately 63 days after ovulation.  This means that the dog, even if not pregnant, experiences some of the symptoms of pregnancy for what would have been the duration of the pregnancy.  With regards to progesterone, the symptoms are behavioural – the dog will be more pessimistic, will be more likely to fight to protect resources, will be more vigilant and will startle more easily – behaviours that would protect the in utero pups, if the dog was pregnant.

In summary female dogs will be more reactive for approximately 63 day after their season.

Prolactin

Prolactin is the hormone of maternal behaviour and milk production.  As progesterone starts to fall, prolactin will start to rise, and will peak at 40-60 days after ovulation and then declines if there is no pregnancy.

Normally hormones will return to basal levels, on average at about 60-65 days, but with a range of 45-90 days.

During the season the dog in effect has a phantom pregnancy.  Most of the time there won’t be any physical signs.

Physical signs of a phantom pregnancy

• mammary enlargement
• lactation
• anorexia
• weight gain
• abdominal enlargement
• vomiting
• diarrhoea
• excessive toileting
• excessive eating
• excessive drinking

Behavioural signs of a phantom pregnancy

• nesting
• carrying, hoarding and mothering of objects
• digging or destructive behaviour
• licking
• agression
• anxiety, agitation, increased reactivity
• other changes in demeanour such as lethargy

These symptoms should disappear as the prolactin returns to basal level, but please do consult your vet if your dog is experiencing any of these symptoms.

Vets will typically spay 14 weeks after the ‘last’ day of the season.  There are a few potential problems here.

• The vets won’t always be given accurate information, so make sure that you record in your diary the first day of bleeding, and if possible the last day too to make it easier for the vet to calculate.
• Emerging research is suggesting that prolactin may be elevated at this point.  When a bitch is spayed the body loses the trigger for prolactin to return to basal levels, so if the bitch is spayed when prolactin is elevated the bitch is left in a permanent state of phantom pregnancy; anxious, more likely to over react and potentially aggressive.  Remember, a phantom pregnancy doesn’t always have physical signs.  Many owners wouldn’t make the connection between the change in behaviour and the spay, so they don’t seek help.

There’s ongoing research into persistent pseudo pregnancy, and not a great deal of statistics at the moment, but some extrapolating from some studies on dogs euthanised for behavioural reasons suggest that as many as 33% of female dogs could be experiencing it.

Could you avoid this issue completely by spaying before the first season?  Yes, but then you’re opening the doors to other issues such as cancers and inhibiting development of the brain thereby leaving the dog in a permanent juvenile state.

There’s bad news and good news.  The bad news is that currently there’s no reliable test; prolactin is always present and the level of prolactin isn’t indicative of the level of the problem.   The good news is, as long as you recognise that your dog is experiencing a persistent pseudo pregnancy, you can ask your vet to treat; it’s medicine for 6-14 days, you should then see a magical difference in your dog (although it should be recognised that you may need professional help with some behaviours that have been practiced for a length of time).