Fetal development during pregnancy is an intricate, continuous process where a single fertilized cell transforms into a fully formed human baby over approximately 40 weeks. This growth occurs in stages, broadly divided into three trimesters, each marked by specific milestones.

In the first trimester (weeks 1–12), rapid cell division and organ formation occur. By the end of this phase, the fetus develops a beating heart, a functioning brain, and basic structures for limbs, eyes, and ears. The placenta and umbilical cord, responsible for nutrient and waste exchange, also form during this stage.

The second trimester (weeks 13–26) is characterized by significant growth. The fetus becomes more active, and movements can often be felt by the mother. Facial features become distinct, and organs like the liver, pancreas, and kidneys begin functioning. By week 20, a detailed anatomy scan ultrasound checks for structural abnormalities. The fetus develops fine hair (lanugo) and a waxy coating (vernix caseosa) to protect its skin in the womb.

The third trimester (weeks 27–40) focuses on maturation and weight gain. The brain undergoes rapid development, the lungs mature to prepare for breathing, and fat stores accumulate under the skin. The baby’s movements become stronger and more coordinated. By 36 weeks, most babies settle into a head-down position in preparation for delivery.

Fetal growth can be influenced by maternal factors such as nutrition, health conditions, and lifestyle choices. Monitoring fetal growth through ultrasounds and measuring fundal height ensures that the baby is developing appropriately.

Ultimately, understanding fetal development helps parents appreciate the importance of prenatal care, healthy habits, and timely medical intervention in ensuring a healthy pregnancy and childbirth.