During the 5th week of pregnancy, several significant developments occur:

1. Embryo Growth: The embryo continues to grow rapidly. It is now about the size of a sesame seed, measuring approximately 0.13 inches (3.3 millimeters) long.
2. Formation of Major Organs: The major organs and systems, including the heart, brain, spinal cord, and circulatory system, begin to form during this week. The heart starts to beat, although it may not yet be detected on ultrasound.
3. Neural Tube Development: The neural tube, which eventually develops into the brain and spinal cord, starts to close. This process is critical for the healthy development of the baby’s nervous system.
4. Primitive Circulatory System: Blood circulation begins as the baby’s primitive circulatory system takes shape. The heart starts pumping blood, although it is still very basic at this stage.
5. Placenta Formation: The placenta, an organ that provides oxygen and nutrients to the embryo and removes waste products, continues to develop and grow. It plays a crucial role in supporting the baby’s growth throughout pregnancy.
6. Symptoms for the Mother: Some women may start experiencing early pregnancy symptoms such as fatigue, nausea, breast tenderness, and frequent urination. These symptoms are due to hormonal changes occurring in the body to support the pregnancy.

It’s important for expectant mothers to continue taking prenatal vitamins, eating a balanced diet, staying hydrated, getting regular exercise (if approved by a healthcare provider), and attending prenatal appointments for proper monitoring and care.