Excerpted with permission from
Adventures in Tandem Nursing: Breastfeeding During Pregnancy and Beyond
by Hilary Flower
Now this is a tricky question. Of course if early pregnancy nausea has dampened your appetite, and especially if vomiting occurs frequently, it is common to gain weight slowly or even lose weight during the first trimester. But when some of the calories you do keep down are going to make milk, it is natural to wonder if perhaps you would be better off conserving those calories by breastfeeding less or weaning completely.
You will do well to avoid feelings of guilt about your limited resources being divided between the placenta and breast milk; but instead give careful consideration to just what is in the best interest of the three of you. Some mothers have continued breastfeeding, counting on a rebound after the nausea subsides in mid-pregnancy, and sometimes counting also on fat reserves they had going into pregnancy. Others feel that weaning or reductions in nursing are necessary to adequately care for the fetus.
As you evaluate your situation you will want to take into account: your rate of weight loss, your total weight loss so far, your number of weeks gestation, your fat reserves going into pregnancy, your weight-gain pattern last pregnancy, and how much milk you are producing. Your caregiver can help you evaluate what is called for in your situation, whether it is weaning, a dietary adjustment, a new way to work with nausea, or simply abiding with patience.
Several studies corroborate the generally held belief that second and third trimester weight gains are believed to have the most impact on fetal growth. Twenty weeks is often considered a time by which the mother should be gaining well, about one pound (0.4 kg) per week.