The reports I have read all say that she and her family were aware that she had WPW ( Wolff Parkinson White syndrome). This makes sense, as I do not believe she had a pulse when found.
Also, it appears that she had gained quite a bit of weight during her pregnancy aside from baby weight, which likely put extra strain on a heart with an electrical conduction disorder which can become fatal in a hurry.
Looking at the known risks of ventricular fibrillation or sudden cardiac death with WPW, she was or should have been noted as a High Risk Pregnancy. Maybe she was, and maybe this is one of those things which couldn't be predicted. I know I wouldn't think to tell a very pregnant teen not to shovel show, because it would never cross my mind that she would attempt to do so. ( Any pregnant young woman, not just this one.)
I've seen several adult ( non-pregnant) patients during my long career in critical care with either known WPW or idiopathic WPW in the presence of another cardiac cycle disorder. Usually they became unconscious due to a heart rate that can be as fast as 300 BPM, which is incompatible with life. 911 was called, and I saw them first when a " Code Blue "was called in ER. It is very easy for the uninitiated caregiver to mistake WPW for Ventricular Tachycardia, and sustained V Tach is a Code Blue situation.
The problem with WPW is that it can, under physically stressful conditions, cause poor perfusion, unconsciousness and an emergency treatment situation all by itself when the ventricular contraction rate ( which is measured as the heart rate) gets so high. WPW can be refractory to cardioversion ( a synchronized zap with the defibrillator) and all meds. which treat supraventricular tachycardia, or SVT and lead to the quickly fatal heart quivering known as. V. fib.
Therefore, it is accurate to state that WPW is fatal when the cardioversion and IV medications do not change the extremely fast ( sometimes too fast to count) heart rhythm back to a normal , or in the case of a WPW patient, a near- normal beating heart with an atrial- ventricular pattern.
To put it more simply, WPW is an electrical conduction defect in the heart, and can cause extremely chaotic, runaway fast heart beats which can be extremely hard to stop. Cardioversion is the best treatment, usually.
Thus, it would be an understatement to say that it would not be unusual at all for a pregnant young woman with known WPW to be in a very precarious condition with or without emergency treatment after the exertion of shoveling snow. Exercise in the cold was probably what pushed her heart into a fatal abnormality which was not self- correcting. Also, there is a fairly high chance that if a trained medical team had been right beside her the second she began having problems, her life could not be saved due to the extreme existence of adverse cardiac factors, which are around 4 separate often- deadly risk factors all on their own.
Since this is an opportunity to teach, I'd like to end this very sad and also complicated cause of death with the following message to all my fellow WSers regardless of age, sex, or general- well being or perceived good health.
If you have had episodic chest pain or any other sign indicative of possible heart disease, of if you have a known heart disorder or disease, please do not over- exert yourself in extremely cold conditions. Leave your snow to melt on its own if you can, pay someone who works outdoors frequently in the cold weather to shovel your snowy walkway, or buy a snow blower if you live in a cold environment. It could save your life.
Likewise, if you doctor has prescribed sublingual Nitroglycerine for angina, keep it with you, make certain it hasn't expired and take one at the first sign of discomfort, and also a regular aspirin unless you have been told not to, and go to the hospital ER if rest, a warm indoor environment and 2 NTG tablets under the tongue do not relieve the pain in 20 minutes. If you are having some heart issues, please try very hard to stay OUT of the cold weather as much as possible. More deaths from heart attacks and sudden cardiac death occur in the winter time than any other time, and both vasoconstriction and exercise are serious contributing factors.
This is not meant to be " bossy". I don't walk that way. It is an opportunity to use a very tragic loss of a young lady and her unborn child to illustrate both the dangers of uncontrolled ( or uncorrected cardiac conduction defects) as well as the increased stress, thus increased risk, to every heart in severe cold and exertion.
I love you all dearly, and want you to be around for more years than i can count. 
