The professional-body position, in its own words
Pregnancy and childhood are where care matters most and where hearsay does the most damage, so here the sources speak and we mostly get out of the way. The Academy of Nutrition and Dietetics is the largest organization of registered dietitians in the US. Its 2016 position statement is quoted in full on this point.
Primary source 01 / 05
It is the position of the Academy of Nutrition and Dietetics that appropriately planned vegetarian, including vegan, diets are healthful, nutritionally adequate, and may provide health benefits for the prevention and treatment of certain diseases. These diets are appropriate for all stages of the life cycle, including pregnancy, lactation, infancy, childhood, adolescence, older adulthood, and for athletes.
The load-bearing word is 'appropriately planned.' On pregnancy outcomes specifically, the paper is measured about how much is known.
Primary source 02 / 05
Limited research indicates that where food access is adequate, vegetarian pregnancy outcomes, such as birth weight and pregnancy duration, are similar to those in nonvegetarian pregnancy.
The non-negotiable: B12
Planning is not a vague virtue here. It has a specific highest-priority item. The Academy names the stakes.
Primary source 03 / 05
Vegans must regularly consume reliable sources, meaning B-12-fortified foods or B-12-containing supplements, or they could become deficient, as shown in case studies of vegan infants, children, and adults.
The NIH fact sheet is more graphic about why infant B12 status is the sharp end of this.
Primary source 04 / 05
Exclusively breastfed infants of women who consume no animal products might have very limited reserves of vitamin B12 and can develop vitamin B12 deficiency, sometimes very early in life
Primary source 05 / 05
Undetected and untreated vitamin B12 deficiency in infants can result in neurological damage, failure to thrive, developmental delays, and anemia
Read those two quotes as the reason the first section is not a green light to wing it. The position is genuinely reassuring: a planned vegan diet is endorsed for pregnancy, infancy, and childhood by the dietitians' own body. The planning is the whole thing, and B12 leads the list. This page is a summary of the evidence, not a substitute for a doctor or dietitian who knows your pregnancy or your child.

