If an animal has a fetus and it dies, what happens to it at various stages of pregnancy (for a human for example: 1 week, 1 month, 8 months etc)?
It is always just passed out via the vagina, or does it ever get dissolved in the uterus? Does it affect the ability to have more kids having this happen?
It’s actually possible for a fetus to calcify…which certainly affects reproductive ability.
It’s possible for rabbits to reabsorb the fetus(es).
Well perhaps, but your link says that the fetus developed outside the womb, and the reason for the calcification was because the body could not expel it. So the reproductive system seems to be not harmed, however carrying around a fetus shaped stone along with a live pregnancy would seem to cause some issues.
The answer is “It depends.”
Most frequently, a very early pregnancy is passed naturally in what seems like a late menstrual period. It is never reabsorbed. It is thrown out with the menstruation. I believe it is estimated that as many as 50% of first pregnancies may lost early in this way.
This is usually called a ‘miscarriage’ (As are all pregnancy losses in lay terms. The medical term is always ‘abortion’ because the pregnancy was ‘aborted.’) and many things can lead to this such as a blighted ovum or an an empty sac or a chemical pregnancy, etc. Maybe the egg had genetic weirdness and/or didn’t implant or implant well in the uterus.
This may happen so early that a woman may not even realize that she was pregnant, perhaps in the 6 to 8 week range.
Also, the fertilized egg could implant in a wrong place like the fallopian tube.
Losses in the first trimester, up to 12 weeks, and that are also implanted in the uterus are classified as threatened, inevitable, or complete, depending on their severity and risk for loss.
By now most women will realize they are pregnant. She might take steps to preserve a threatened abortion (or miscarriage) such as seeing her doc and getting hormone supplements. Or, she might take steps to terminate the pregnancy medically or surgically.
Early tubal pregnancies can be usually resolved with medications, but may also sometimes require surgery and removal of the damaged tube. A ruptured tubal pregnancy can actually cause death by bleeding if not properly treated. A fertilized egg could also implant outside of the uterus, say in the abdominal wall or someplace. Fortunately this is not common.
There is also the case of a ‘missed abortion’ where the fetus has stopped growing, but the pregnancy makes no effort to pass itself. This generally needs medical and/or surgical intervention.
If the loss is inevitable such as in the case of cervical dilation or leakage of amniotic fluid or contractions, then she might wait to pass the pregnancy naturally (while being monitored closely to ensure completion and prevent infection) or need medical assistance in the form of a vacuum aspiration of the uterus or a dilation and curettage (D&C).
The ‘cleaning out’ of the uterus should be done by a trained medical professional so that there is no damage, such as a puncture to the uterus, and to ensure that all ‘products of conception’ are removed.
These situations can also occur in the second trimester, too- 12-24 weeks. In the second trimester, there is typically medical involvement due to the increase size of the fetus, although these pregnancies can also be lost completely and spontaneously, too.
A complete abortion in the first trimester usually resolves itself without medical intervention such a medications or procedures. It is important that the placenta pass as well as the fetus. If it doesn’t, then a uterine evacuation will be necessary.
Every now and then I hear about the ‘vanishing twin.’ That means at the very first ultrasound, usually done at 6 to 8 weeks, there are two (or more) embryonic sacs noted and that one or more of them have disappeared by the time of the next ultrasound. I suppose they are empty sacs or sacs that did not develop any further. If the ‘surviving twin,’ now perhaps a singleton, pregnancy continues, this old sac will bee too small to notice at delivery.
I have seen situations where a twin died at a later gestation- late first trimester or in the second (or even third) trimester. These pregnancies usually go one of two ways- no problem and the deceased (and squished) twin delivers with the survivor, or the woman becomes very, very ill and must be delivered of the pregnancy to save her life, no matter the gestation or chance of survival to the fetus.
How the loss will affect future pregnancies also depends. If a tube is lost, conception could be more difficult (ovaries sorta take turns spitting out eggs, so ovulating on the side without a tube would not be helpful in conceiving).
The cause of the loss, if it can be found out, plays a role- structural defects in the uterus or cervix, genetics issues, hormonal problems such as lack of progesterone (‘pro-gestation hormone’).
If infection developed, there could be scarring in the tubes or uterus causing future problems.
But, if the loss ‘went well,’ there should not be any reason to worry too much about the future.
I just want to note that one possible complication of a pregnancy gone wrong is choriocarcinoma, where cancer develops (usually from the placenta).
Fortunately, it is a rare disease. Also fortunately, the cure rate for these pregnancy-related cancers these days is around 90-95% if caught in time.
Another possible fate is that of the human chimera, and individual whose body has more than one genome. The merging of fraternal twins is one way this might occur. Although once considered vanishingly rare (as in no cases known) modern genetic testing is finding that such folks do exist and for the most part look pretty normal.
Both of the above occur in animals as well, of course.
Referring to the term “animal” used by the OP, fetal death in sheep and goats tends to go unnoticed until the mama sickens from the rotting mess in her uterus. Removal of the dead tissue and lots of antibiotics may save the mama but the vet bills tend to be more than the animal is worth.