21- Sheep have a gestation of 147 days. When the ewe is ready to lamb, the interior of her should be set up like this for and ideal birth.
If the ewe is having trouble lambing, chances are the lamb/s is/are either very large or that the lamb/s is/are not in the correct position.
Here are some of the possible other positions:
Breech
Elbow Lock
Four Legs - One Head
Head Back
Hind Legs Only
One Leg Back
Twins - Front and Back
Both Forelegs Back
Here is a video pointing out many aspects of lambing and actual footage of a lamb birth.
