Forensic Author Question: Fetal Bones

This month, Amryn has another great author question to answer.
Gloria F. asks: At what fetal age would bones show up with mom’s if mom was killed & stuffed in locker for 15 yrs? The body has been above ground in a disused bldg for that length of time.
Amryn says:
It’s important to understand that there are always exceptions to every case, so the answers I give are generalized unless otherwise stated. That being said, there are a couple factors at play here.
First of all, the process of skeletonization will vary with temperature and humidity. In this case, 15 years would be sufficient time for both the mother and the fetus to be skeletonized. This process can actually take as little as a few weeks in a hot humid environment. This is the sort of research done at the Body Farm (see my previous post for more info.)
A fetus will begin to develop its skeletal system around 12 weeks. From that point forward, the bones will grow harder and more dense. Theoretically, you could find fetal bones as early as approximately 15 weeks of gestation. The problem with this is, the bones are not fully articulated and would be very easy to scatter. Also, if you consider the average size of a fetus at 15 weeks, it only measures about 6 inches long. Those are some very tiny bones!
That’s not to say they couldn’t be detected by an anthropologist or medical examiner, but I would guess it’s more likely to find them if they suspect the woman may have been pregnant. Obviously the larger the bones, the easier they’ll be to see.
Another thing to consider is the idea of coffin birth or postmortem fetal extrusion. Basically, as the woman began to decompose, gases would build up in her body and could force the baby from her uterus… almost as if she was actively giving birth. This articleexplains it well. It’s something to consider as the fetal bones may not be found “inside” the woman when her remains are discovered.

Amryn Cross is a full-time forensic scientist and author of romantic suspense novels. Her first novel, Learning to Die, will be released in September. In her spare time, she enjoys college football, reading, watching movies, and researching her next novel. You can connect with Amryn via her website, Twitter and Facebook.

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