Pregnancy is a period of intense and rapid development for both the mother and the fetus. Physiologically, anatomically, and psychologically, the rapid transformation of an embryo into an infant and of a woman into a mother is unparalleled. Although not a comprehensive review of pregnancy, this chapter discusses maternal and fetal development in each of the three trimesters, considering the physical and psychological changes that take place.
TRIMESTER 1: WEEKS 1 TO 12
The first sign of pregnancy for most women is a missed menstrual period. Other early signs of pregnancy are tenderness of the breasts--a tingling sensation and special sensitivity of the nipples--and nausea and vomiting (called morning sickness, although it may occur at any time of the day). More frequent urination, feelings of fatigue, and a need for more sleep are other early signs of pregnancy. A wide variety of reactions may follow the discovery of a pregnancy. For the woman who has been trying to conceive for several months, the reaction may be joy and eager anticipation. For the teenager who does not feel ready to become a mother, the adult woman who does not want to have children, or the adult woman who feels that she already has enough children, the reaction may be negative--depression, anger, and fear. The presence of a supportive social network is particularly important for such women at this time. The decision to end or continue the pregnancy is typically made within the first trimester.
The relationship between the mother and her partner may begin to change after the discovery of pregnancy. Although a range of patterns and frequencies in sexuality is normal, sexual desire and activity may decrease during pregnancy. Most women attribute this change to fatigue. Expectant fathers are sometimes initially ambivalent about their approaching father role, but trends in North America show fathers becoming more involved in parenting and childbirth preparation. For the couple eagerly awaiting the birth of their new baby, pregnancy can be a time of increased intimacy and relationship satisfaction.
The basic physical change that takes place in the woman's body during the first trimester is a large increase in the levels of hormones, especially estrogen and progesterone, which are produced by the placenta. Many of the other physical signs of the first trimester arise from these endocrine changes. The breasts swell and tingle, resulting from the development of the mammary glands, which are stimulated by the hormones, and the nipples and areolas may darken and broaden. There is often a need to urinate more frequently, which is related to changes in the pituitary hormones' effects on the adrenals, which in turn change the water balance in the body so that more water is retained. The growing uterus also contributes by pressing against the bladder. About 75% of women experience morning sickness, which may be due to high levels of estrogen irritating the stomach. Vaginal discharges may also increase at this time, partly because of the increased hormone levels, which change the vaginal pH, and partly because the vaginal secretions are changing in their chemical composition and quantity. The feelings of fatigue and sleepiness are probably related to the high levels of progesterone, which is known to have a sedative effect.
The development of the fetus during the first trimester is rapid: the small mass of cells implanted in the uterus develops into a fetus with most of the major organ systems present and with recognizable human features. During the third and fourth weeks, the head undergoes a great deal of development as the central nervous system begins to form, and the beginnings of eyes and ears are visible. By the end of the 10th week, the eyes, ears, arms, hands, fingers, legs, feet, and toes are completely formed. By the end of the 7th week, the liver, lungs, pancreas, kidneys, and intestines have formed and have begun limited functioning. Although the gonads have also formed, the gender of the fetus is not clearly distinguishable until the 12th week. From this point on, development consists mainly of enlargement and differentiation of structures that are already present.
TRIMESTER 2: WEEKS 13 TO 26
During the fourth month, the woman becomes aware of the fetus's movements, known as quickening. Many women find this to be an exciting developmental milestone in their pregnancy. In addition, the experience may lessen anxiety about a miscarriage. Around the same time, the physician or midwife can detect the fetal heartbeat. The mother is made even more aware of the pregnancy by her rapidly expanding belly. Some women feel that it is a beautiful and powerful symbol of womanhood; other women may feel awkward and resentful of their bulky shape and may feel insecure about their physical attractiveness.
Most of the physical discomforts of the first trimester, such as morning sickness, disappear in the second trimester. For this reason, the second trimester is usually a period of relative calm and well-being. As a result of the mother's physical changes, constipation (caused by increased progesterone, which inhibits smooth muscle contraction) and nosebleeds (caused by increased blood volume) may occur. For some women, edema may be a problem in the face, hands, wrists, ankles, and feet; it results from increased water retention throughout the body.
By about midpregnancy, the breasts, under hormonal stimulation, have essentially completed their development in preparation for lactation. Beginning about the 19th week, a thin amber or yellow fluid called colostrum may come out of the nipple. Around this same time, the fetus first opens its eyes. By about the 24th week, the fetus is sensitive to light and can hear sounds in utero. Arm and leg movements are vigorous at this time, and the fetus alternates between periods of wakefulness and sleep. These patterns are detected by the mother, whose bond to her developing fetus may strengthen as she becomes more acquainted with its activity.
Throughout pregnancy, it is important that the mother obtain adequate nutrition to support herself and her fetus. Folic acid, calcium, iron, vitamin A, magnesium, and protein are important for maintaining the mother's health and fostering the healthy development of the fetus. Some drugs, such as antibiotics, alcohol, cocaine, marijuana, nicotine, and some prescription drugs, may adversely affect fetal development and lead to birth defects, preterm labor, or even miscarriage.
For about 10% of women, pregnancy may be accompanied by depression. Although women with a history of depression are at increased risk for depression during pregnancy, the depressive episode during pregnancy is the first such episode for about one third of depressed pregnant women. Other risk factors include poor marital quality, inadequate social support, low socioeconomic status, an unwanted pregnancy, and negative life events. Depression during pregnancy increases risk for health problems during pregnancy (e.g., poor fetal weight gain, drug use, and noncompliance with health care) and in the postpartum (e.g., child cognitive, social, emotional, and health problems, as well as postpartum depression). Although the U.S. Food and Drug Administration (FDA) has not approved the use of antidepressant medications during pregnancy, many studies suggest that some antidepressants may safely treat depression during pregnancy.
TRIMESTER 3: WEEKS 27 TO 38
The mother's uterus is very large and hard now, which puts pressure on her other organs and may cause some discomfort. The pressure on the lungs may cause shortness of breath. The stomach is squeezed, often leading to indigestion. The heart is also somewhat strained by the large increase in blood volume. Sleep can also be difficult because of the increased size of the uterus and increasing activity level of the fetus. These physical changes are often accompanied by a further decrease in sexual desire on the part of the mother because the mother's shape may make sexual intercourse uncomfortable at this time.
The weight gain of the second trimester continues in the third trimester, sometimes causing a disturbance in the mother's sense of balance and an increase in lower back pain. Although women typically gain 20 to 30 pounds during pregnancy, excessive weight gain can be a sign of gestational diabetes. Regular aerobic exercise during pregnancy can improve or maintain physical fitness and has not been conclusively shown to be associated with any risks. At the end of the 8th month, the fetus weighs an average of 2,500 grams. The average full-term baby weighs 3,300 grams and is 50 centimeters long.
During the seventh month, the fetus turns in the uterus to assume a head-down position. If this turning does not occur by the time of delivery, there will be a breech presentation. Women can do certain exercises to aid the turning. Physicians and midwives can also perform certain procedures to turn the fetus. Moxibustion (a technique used in Chinese medicine) can be performed by an acupuncturist to aid turning as well. In the last month, the fetus will begin to descend into the pelvis (called engagement), sometimes creating slight discomfort in the perineum. During the third trimester, the uterus may also tighten occasionally in painless contractions (called Braxton-Hicks contractions). Although not a part of labor, these contractions may help strengthen the uterine muscles in preparation for labor.
A mother and her developing fetus experience tremendous and rapid development during pregnancy. As adequate prenatal care and nutrition contribute to the healthy development of the fetus, a supportive social network contributes to the psychological wellbeing of the mother.
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