In just 40 weeks, two 23-chromosomal cells called haploid cells join together, grow and form into a unique human baby. The process is a biological wonder that is fascinating and exciting for any parent. Knowing what happens in the womb at each stage can help a woman connect with and understand the growing life inside of her.
Conception
Conception is the point at which an ovum and sperm join together to form a zygote, beginning the first stage of developing life. The zygote grows rapidly, dividing in half to create two cells within the first 30 hours. It travels through the fallopian tube to the uterus carrying all the necessary information to create a baby. It continues to divide exponentially. The tiny, bumpy ball of cells, called a blastocyst, implants itself into the uterine wall. The outer layer of cells will become protective and nourishing membranes. The inner layer will form the embryo.
Embryonic
Fourteen days after conception, the zygote becomes an embryo. The embryonic stage is important for development, and at this time the embryo is the most susceptible to abnormalities, especially from exposure to toxins. Internal and external structures and organs begin to form. The heart begins to beat during this stage, around four weeks after conception. Each day, the embryo appears more human-like. At this point, the embryo has grown to 1 1/4 to 1 3/4 inches in length and weighs about 5 grams. The embryonic period ends at week 10 of pregnancy, or eight weeks post conception.
Fetal
The fetal stage begins eight weeks after conception and continues until the baby is born. Growth is rapid and many changes take place as the fetus prepares for life outside the womb. Organs, systems and external structures continue to grow and begin to function throughout the entire fetal period. A heartbeat is easily heard through a Doppler instrument. About 14 weeks after conception, a woman may be able to feel the fetus move. This is referred to as the quickening. As time moves forward, the fetus will begin to swallow amniotic fluid, suck his thumb and open his eyes. He will also be able to hear sounds within the womb as well as outside of it. When the fetus reaches the age of 22 weeks, he may be able to survive outside of the womb if the proper medical care is available. This is called the age of viability. The fetus will begin to store nutrients and build body fat. The lungs mature approximately at 34 weeks of age. Near the end of the pregnancy, the fetus will position himself head-down in the uterus to prepare for birth. Organs are functioning and appendages are fully formed. The fetus is ready to sustain life on his own.
Birth
Though only 5 percent of babies are born on their due date, the average length of a human pregnancy is 40 weeks. Around this time, the uterus begins to contract and the cervix dilates. When the cervix dilates to 10 cm, the fetus travels down the birth canal to the vaginal opening. With the aid of the mother, the fetus is pushed through the vagina and is born. She is now a baby. The birth process ends shortly thereafter with the delivery of the placenta.
References
- "Your Pregnancy Week by Week"; Glade B. Curtis, M.D., M.P.H., OB/GYN and Judith Schuler, M.S.; 2004
- "The Developing Person Through the Life Span"; Kathleen S. Berger; 2005
- "Contemporary Nutrition: A Functional Approach"; Gordon M. Wardlaw and Anne M. Smith; 2009
