Ma's first escape attempt was caused by her realizing she was pregnant with Jack.
Ma said she was kidnapped in late January. This means her escape attempt that occurred a year and a half later took place in July of the following year...nine months before Jack's birth the next March. Ma recognized the symptoms of pregnancy from her two previous ones, which initiated such a bold escape attempt.
Old Nick was a war veteran.
The intricate way he built that shed (presumably on his own), specifically so no one could escape with the barbed wire not to mention the keypad on the outside implies some sort of military training.
