Ty and Amy's storyline was one of the strangest in the show's nine-plus seasons. First, Bob's passion for the Gobi bears seemed abrupt and out of character. The character has always been laid-back and accepted that some animals can't be saved; suddenly he's full of zeal for this cause in Mongolia. Second, he seemed puzzled that Ty would want to stay with his pregnant wife. A veterinarian especially should understand a father's instinctive need to stay close to his pregnant mate.
Third, for Ty, deciding whether to tend to Mongolian bears or his pregnant wife should have taken about two seconds. Amy will have enhanced emotional, physical, and financial needs during her pregnancy. It is Ty's direct responsibility to fill those needs - not his father-in-law, grandfather-in-law, or anyone else.
It might have been more understandable if Ty were offered a chance to make more money by working a few months in a reasonably distant location, say Toronto or the US. But a volunteer mission to save endangered bears on the other side of the world? Come on! The writers even seem to address the absurdity through Tim's outburst at the dinner table.
Fourth, Amy is naïve about the support she will need during her pregnancy. She seems to think pregnancy will be a breeze and won't affect her normal routines too much. But this is actually in harmony with her character, so realistic enough.
Heartland is an interesting show. Sometimes it depicts family relations realistically. Peter and Lou's breakup has seemed almost painfully realistic. Other times, it is totally unrealistic - for many episodes, Jack and Lisa's marriage seemed more like a friendly business relationship. In this episode, a realistic relationship takes an unrealistic turn. It's still the best show on television, though.