1. My sim was not full term at the time of these pics - poses have been designed to accommodate for full term
2. Secondly, large balls for the sim to lean on, small balls for sitting on. When placing the balls, watch the direction of the arrow. Place towards or away the sim, depending on the pose. The tennis ball goes onto the OMSP and raised up into place.
3. I have altered some of the poses for larger sized sims. Those poses have a letter after the number.

Codes

a_bmit_labour1 (resting on large ball, kneeling)
a_bmit_labour2 (on knees, leaning on ball, finger in mouth)
a_bmit_labour3 (massaging back of pregnant sim)
a_bmit_labour4 (pregnant sim walking with IV pole)
a_bmit_labour5 (resting on ball)
a_bmit_labour6 (using rolling pin on back of pregnant sim)
a_bmit_labour7 (sitting on ball, holding pregnant belly)
a_bmit_labour8 (pregnant sim on bed, leaning on top)
a_bmit_labour9 (hand on back of pregnant sim pose 8)
a_bmit_labour10 (pregnant sim standing and leaning on wall)
a_bmit_labour11 (holding pregnant sim - pose 10, from behind)
a_bmit_labour12 (pregnant sim hugging pose 13)
a_bmit_labour13 (standing and hugging pregnant sim pose 12)
a_bmit_labour14 (pregnant sim squatting)
a_bmit_labour15 (sitting behind pose 14, holding pregnant sim)
a_bmit_labour16 (sitting on ball, hands on shoulders of pose 17)
a_bmit_labour17 (sitting on ball, hands on supporting pose 16)
a_bmit_labour18 (water broke, looking down)
a_bmit_labour19 (goes with pose 20)
a_bmit_labour20 (holding hand of pose 19 or 19b)
a_bmit_labour21 (bending over in pain holding stomach)

Poses for larger sized sims
a_bmit_labour4b (same as pose 4 but for larger sim)
a_bmit_labour6b (altered pose 6 to go with larger pose 5)
a_bmit_labour7b (same as pose 7, but for larger sim)
a_bmit_labour11b (altered pose 11 to go with larger pose 10)
a_bmit_labour12b (altered pose 12 for larger sim)
a_bmit_labour13b (altered pose 13 to go with larger sim)
a_bmit_labour14b (altered pose 14)
a_bmit_labour15b (altered pose 15 to go with larger pose 14b)
a_bmit_labour17b (altered pose 17 to go with larger pose 16)
a_bmit_labour19b (same as pose 19 but for larger sim)
a_bmit_labour21b (same as pose 21 but for larger sim)

Credits: Around The Sims 3