There is a dramatic increase in demand for choline in the 3rd trimester of pregnancy. This corresponds to the rapid expansion of neurodevelopment. Choline is needed to produce phosphatidylcholine and sphingomyelin, the main components of neural cell membranes and myelin. Choline is also the precursor for acetylcholine, a key neurotransmitter in synapses as well as an important regulator of neural growth. Finally, because it is the primary dietary source of methyl groups, choline plays a big role in the 'epigenetic' regulation of genes in the fetus that can have lasting effects throughout the lifespan.