Traditionally, stages during pregnancy are often divided up into weeks or trimesters. Within these common stages in pregnancy are six major times of change. These stages of pregnancy occur at one week, four weeks, eight weeks, 12 weeks, 24 weeks and 40 weeks.
Stages in Pregnancy – Week 1
During the first week of pregnancy, the blastocyst (the result of the egg and sperm joining) embeds in the uterine lining. Implantation bleeding may occur at the time the blastocysts implants. Implantation bleeding may appear as light spotting. Women typically think this spotting is associated with an upcoming menstrual cycle. When the egg is fertilized, HCG is released to keep the corpus luteum alive. The corpus luteum releases progesterone needed for the maintenance of fetal health and the progression of pregnancy.
Stages in Pregnancy – Week 4
By the 4th week, there is an embryo and a yolk sac. This will appear on an ultrasound as a dark circle. The embryo does not have any distinguishable features at this point, but growth is rapid and soon an ultrasound will show arm buds and leg buds. By the 4th week of pregnancy, women typically feel the effects of pregnancy though they may not know they are pregnant yet. Soon, the pregnant woman will miss her first period.
Stages in Pregnancy – Week 8
Now the embryo is called a fetus. The yolk sac is gone and the placenta is growing. The fetus is still very tiny so an ultrasound will not produce a picture that looks even remotely like a baby at this point. Women typically find out they are pregnant sometime around the 8th week of pregnancy. Breasts may be tender and morning sickness may already be starting. HCG levels can be measured in urine tests.
Stages in Pregnancy – Week 12
An ultrasound in the 12th week of pregnancy would show a strong heartbeat, placenta, umbilical cord, arms, and legs. This is the end of the first trimester, which is often a relief for many women. Women may choose to wait until the end of the first trimester before telling friends, family and coworkers they are expecting.
Stages in Pregnancy – Week 24
The 24th week is an important time for the fetus. Chances of survival after early delivery increase greatly with every passing week. Infants born at 24 weeks gestation may have an extended hospital stay as lungs are still developing. An ultrasound will show arms, legs, and gender for parents who are interested in know the sex of the baby.
Stages in Pregnancy – Week 40
The room in the womb has run out by this time in pregnancy. Movement by the fetus has slowed down a bit because there is simply no room to kick and roll. The fetus is completely developed and ready for birth. Women who do not start natural labor by the 42nd week are often induced due to increased risk of prolonged pregnancy.