Back ache/sciatica and pelvic girdle pain

As your pregnancy progresses and the baby gets bigger the pressure on your pelvis, back or vagina increases. If this is feeling uncomfortable adjust your activity accordingly. Don’t give up exercise entirely but modify your activities and listen to your body It you’re experiencing a lot of pain acupuncture can be a safe effective alternative to pain killers. Research from Sweden concluded that when compared to physiotherapy, acupuncture was the treatment of choice for vaginal pressure and sacroiliac pain.

Backache
Backache in the final trimester of your pregnancy is very common as you're carrying more weight, your center of balance is off and your posture is probably not as good as it used to be.
Backache can be very uncomfortable but again it is your body’s way of saying slow down and rest. In addition you may be able to decrease the severity or the frequency of your back ache by following a few simple tips:

• Sleep on a firm mattress
• Put a pillow between your knees and at the small of your back
• Watch your posture 
• Alternate standing, sitting, and reclining; Don’t stay in one position for too long a period of time extended periods of time
• Exercise and stretch --prenatal yoga can be especially helpful
• Try alternating heat and ice packs to the painful area
• Wear comfortable shoes with good support Avoid high heels
• One to two weekly acupuncture treatments can help relieve back pain

Note: If you have sudden and/or intense back pain in the last weeks of pregnancy you may actually be labour!

Sciatica
Sciatica is severe pain, weakness, or numbness of the lower back, buttocks and thighs that radiates from the side of the thigh to the front of the lower leg. This pain is usually concentrated on one side of the body. As your pregnancy progresses and your baby grows the head exerts more pressure on your pelvis.  For some women this pelvic pressure actually stretches the sciatic nerves which are located in the back and buttocks. Stretching or pressure on the sciatic nerve causes intense pain, weakness, and numbness.