The first two months of pregnancy mark the end of the embryonic period, corresponding to the completion of the eighth week of gestation. This phase is defined by the rapid organization of cells into tissues and organs. At this stage, the foundation for every major body system is established, marking a significant shift in development. Understanding this period offers a profound appreciation for the initial growth occurring within the womb.
Defining the Size and Scale
At the eight-week mark, the baby’s size is measured using the Crown-Rump Length (CRL), the distance from the top of the head to the bottom of the buttocks. The baby measures approximately 15 to 20 millimeters, or about half an inch to three-quarters of an inch long. This measurement indicates a growth spurt, as the baby increases in size by about one millimeter each day. To visualize this scale, the baby is comparable in size to a common raspberry or a small olive. The following week will mark the beginning of the fetal period, where growth in size will become the primary focus.
Key Features and Appearance
At the end of the second month, the baby’s appearance is characterized by a disproportionately large head, accounting for nearly half of the Crown-Rump Length. The head is beginning to uncurl, and early facial features are becoming visible. Dark spots mark the forming eyes, though they are still widely spaced and covered by developing eyelids. The developing ears are visible as small folds of tissue, and the tip of the nose is beginning to show.
The limb buds have elongated, and indentations are apparent where the webbed fingers and toes will separate. The arms are developing faster than the legs and show bends at the elbow and wrist. The small, tadpole-like tail that was present earlier is now noticeably shrinking.
Internal Systems Development
All major organ systems are established behind the external changes. The brain is undergoing rapid growth, dividing into the forebrain, midbrain, and hindbrain. This central nervous system development is supported by the earlier formation of the neural tube, which will become the spinal cord and brain.
The cardiovascular system is highly functional, with the heart beating rhythmically, often averaging between 140 and 170 beats per minute. Within the limbs, soft cartilage is being laid down to form bones, and primitive muscles are developing. The baby is making spontaneous, twitching movements, although they are too subtle to be felt by the mother. The digestive tract is also developing, undergoing a temporary process called physiological gut herniation. By the close of the eighth week, the baby has completed the most sensitive stage of organ formation.