10.6: Pregnancy from the mother's perspective
Human pregnancy lasts approximately 40 weeks from the time of the last menstrual cycle to childbirth (38 weeks from fertilization). In many societies' medical and legal definitions, human pregnancy is somewhat arbitrarily divided into three trimester periods, as a means to reference the different stages of fetal development. The first trimester period carries the highest risk of miscarriage (spontaneous death of embryo or fetus). During the second trimester, the development of the fetus can start to be monitored and diagnosed. The third trimester marks the beginning of viability, which means the fetus might survive if an early birth occurs.
Changing Body
As soon as a woman becomes pregnant, her body begins to change so that it can support both herself and the unborn baby. All of the body functions start to work much harder. The heart has to pump more blood around the body, in particular to the womb, placenta, and the fetus. As well as physical demands, pregnancy also causes a range of emotional reactions.
First Trimester (1-12 weeks)
- Tiredness, nausea, constipation, frequent urination, food cravings, breast tenderness, change in size of breasts, fainting or dizziness, bloated stomach, and high emotions.
Second Trimester (13-27 weeks)
- More energy, constipation, heartburn, and indigestion. The breasts continue to grow, as does an increase in appetite. There is mild swelling in the feet, ankles, hands, and face. There is also more baby movement. There may be emotional ups and downs in the feeling of pregnancy, and short-term memory may be poor.
- The hormones estrogen, progesterone, human placental lactogen, oxytocin, and prolactin prepare the body for feeding the baby, and cause the breasts to enlarge, becoming painful and tender.
- The fetus, placenta, and amniotic fluid account for just over a third of the weight gain during pregnancy. The remaining weight comes from increased blood volume, fluid retention, and extra body fat. The suggested weight gain in most pregnancies is between 25-40 lbs.
Third Trimester (28-40 weeks)
- The body is changing to cope with the ever increasing size of the womb. The baby grows and pushes out the lower back of the mother. The breathing rate of the baby is growing very quickly. At this stage, the mother should feel the movements of the fetus. Other signs may be the nipples secreting colostrum, Braxton-Hicks' contractions may begin, and blood flow to the womb has increased tenfold since conception.