What is pseudopregnancy?
False pregnancy or pseudopregnancy is a condition in the mare where she appears to be in foal and all her reproductive systems react accordingly even though she is not pregnant. This mare does not come into season and her body begins to prepare for carrying and nourishing a foetus that does not exist. During this period, valuable reproduction time is being wasted.Could a mare go to full term with a False Pregnancy?
Yes, a mare with a false pregnancy could go to full term but this is not commonly seen to occur.Some of these mares that are presumed to be pregnant can often even put on weight as the false pregnancy progresses in time. One could suggest that this may be due to increased feeding by the owner presuming that the mare is carrying a developing foetus.Some mares may develop mammary or udder development during a false pregnancy. On rare occasions, I have seen mares walk their box and ‘run milk’ as in the normal pregnant mare getting ready to foal. This phenomenon of pseudpregnancy up to full term is quite common in bitches but is rare in mares.Could a non-pregnant mare or filly develop udder enlargement or run milk?
Yes this occurs on occasions, even in fillies. The cause is often unknown but may be due to increased feed especially good grass.How is this condition treated?
On occasions it has been treated successfully with male hormones.Is pseudopregnancy a common problem in mares?
Approximately 5 to 10% of oestrus cycles end in false pregnancies in mares. Therefore it is important for the breeder to know how to identify the problem at an early stage. In other words to have the mare scanned or re-scanned up to 42 days, to make sure that she is either pregnant or not in-foal.This means that being familiar with each mare’s oestrus cycle pattern is essential in order to be able to recognise any deviations or abnormalities that may be developing. This will prevent unnecessary waste of the valuable early breeding season.In order to understand an early pseudopregnancy, it is essential to understand the normal oestrus cycle in the mare.What is the normal pattern of the oestrus cycle in the mare?
The normal mare ovulates follicles or “pops the eggs” one to two days before she goes out of season. A corpus luteum, or “CL”, then develops and begins to produce progesterone.The CL of a non-pregnant mare produces progesterone for about 14 or 15 days (during the luteal phase of the oestrous cycle).At the end of that phase, the mare’s uterus must determine pregnancy, a process called “maternal recognition of pregnancy.” First, the embryo produces a chemical signal and second the uterus detects the signal.If the uterus does not find that signal, the lining of the uterus releases prostaglandins that travel through the bloodstream to the ovary and destroy the CL. Progesterone levels drop rapidly, and the mare develops another follicle and returns to heat. This cycle repeats itself multiple times each breeding season in a non-pregnant mare.If an embryo is present, no prostaglandins are released, the CL is preserved, and more progesterone is produced, keeping the mare out of season.Progesterone is a key hormone for maintenance of pregnancy. It also prevents the mare from returning to heat.How does a pseudopregnancy develop in the normal mare?
In some instances, a non-pregnant mare’s CL can produce progesterone beyond the normal two-week lifespan and a mare will not return to oestrus. The term for persistent progesterone production by a CL is pseudopregnancy, or false pregnancy.If a mare loses the embryo after “maternal recognition,” false pregnancy can result. Mares have one chance per oestrous cycle to determine their own pregnancy status and to “recycle” themselves if they are not pregnant. How is pseudopregnancy diagnosed?
As false pregnancies are not uncommon, early diagnosis is important. If the condition is not diagnosed and treated the breeding season could be over and missed.While teasing is an invaluable aid in the breeding yard, it is essential not to rely exclusively on teasing to determine whether or not a mare is pregnant.Mares that fail to return to oestrus two to three weeks after going out of heat are not always in foal. An ultrasound examination 14 to 16 days after breeding can determine whether a mare is pregnant and detect the presence or absence of twins. A recheck at 25 to 35 days can verify whether the mare is still pregnant.Pseudopregnant mares will not return to heat as long as the CL is producing progesterone. The lifespan of a retained CL can be two to three months.Is it difficult to treat a pseupdpregnancy?
False pregnancy is relatively easy to treat if recognised. A single dose of prostaglandins (PG2) will destroy the retained CL, and the mare will return to oestrus in three or four days. However, the mare must be examined by ultrasound before she receives prostaglandins to be sure she is not pregnant. Pregnant mares that are given prostaglandins will lose their pregnancies.