What weight should I be if I'm 21 weeks pregnant with twins?

Basedon only the information we know, which is that you are having twins, I will assume they are fraternal (because this is so much more common than identical) and that you have reached the 20th gestational week. On average, according to a Clinical Physiology in Obstetrics 2nd ed. Oxford, the following contribute to total maternal weight gain by the 20th gestational week:

fetus #1 - 0.67 lbs.         
fetus #2- 0.67 lbs.
placenta #1 - 0.37 lbs.        
placenta #2 - 0.37 lbs.
amniotic fluid #1 - 0.77 lbs.
amniotic fluid #2 - 0.77 lbs.
uterus - 0.70 lbs.
breast enlargement - 0.40 lbs.
fluid retention - 0.10 lbs.
maternal "stores" - 4.51 lbs.
Total - 9.33 lbs.

I have observed a very, very wide range of weight gain in my patients carrying both singleton and multiple pregnancies and have usually noticed healthy maternal and neonatal outcomes. That is not to say that those patients who are very malnourished or very obverse do not suffer from more complications of pregnancy than those who are not, and these patients should have specific nutritional recommendations discussed with their care-providers. Be assured that the specific weight gain increment, or lack of it, is less directly linked to pregnancy outcome than is popularly portrayed. 

Continue Learning about 2nd Trimester Of Pregnancy

2nd Trimester Of Pregnancy

By your 2nd trimester, most of the fatigue and morning sickness will begin to pass and your next few months will be the easiest of your pregnancy. Most women will begin to show much more obviously than in the 1st trimester because ...

the baby is growing at a very fast rate. The extra weight will often put a strain on your back. Utilize good back support when sitting to alleviate some of the pain. Bleeding gums may start to happen due to your fluctuating hormones but will go back to normal after pregnancy. You may find that your hair is thicker and growing faster than before and often times, will grow in abnormal places. Headaches, frequent urination and heartburn will also be common symptoms.

Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.