Overview Of Pregnancy, Labor, And Related Condition
Characteristics Of Pregnancy And Labor
Pregnancy, which spans 40 weeks from conception to delivery, is divided into three trimesters, with characteristic during each.
Changes During The First Trimester
During the first trimester (weeks 0 through 12) the following occur-
1- Implantation of the fertilized ovum in the uterus occurs 7 to 10 day’s after fertilization.
2- The mother is very fatigued, urinates more frequently, and may experience nausea
and/or vomiting (“morning sickness”).
3- Breast size may increase.
4- There is a relatively small weight gain of 0 to 1455 g (0 to 3 Ib is normal).
5- Emotional changes may occur.
6- By the end of the 12th week, the fetus is 6 to 7 cm long and weighs approximately 20g (2 oz). The fetus now can kick, turn its head, and swallow and has a beating heart, but these movements are not yet felt by the mother.
Changes During the Second Trimester
During the second trimester (weeks 13 through 26) the following occur:
1- The pregnancy becomes visible to others.
2- The mother begins now feel movement at 20 weeks.
3- Most women now feel very good. Nausea and fatigue have usually disappeared.
4- By the end of the second trimester, the fetus is 19 to 23 cm (14 inches) in length and weighs approximately 600 g (1 to 2 Ib).
5- The fetus now has eyebrows, eyelashes, and fingernails.
Changes During the Third Trimester
From week 27 through 40 weeks the following occur:
1- The uterus is very large and has regular contractions, although these may be felt only occasionally.
2- Common complaints during the third trimester are frequent urination, back pain, leg edema and fatigue, round ligament pain, shortness of breath, and constipation.
3- By the time of birth, the baby will be 33 to 39 cm long (16 to 19 inches) and will weigh approximately 3400 g (7 Ib, although a range of 5 to 10 Ib is normal).
Labor is divided into three stages, each containing specific events. The exact mechanism that initiates labor is not know. Regular and strong involuntary contractions of the smooth muscles of the uterus are the primary symptom of labor. True labor produces palpable changes in the cervix, which are known as effacement and dilation. Effacement is the shortening or thinning of the cervix from a thickness of 5 cm (2 inches) before onset of labor to the thickness of a piece of paper.Dilation is the opening of the cervix from the diameter of a fingertip to approximately 10 cm (4 inches).
Some women experience initial cervical dilation and effacement before they are in true labor. However, by the end of this stage, the cervix is fully dilated and there is no doubt that a baby is about to be delivered. Stage 1 of labor is divided into three major phases.
External rotation- The fetus rotates its occiput toward the mother’s sacrum to allow the fetal shoulders under the symphysis pubie, and the rest of the body.
- Placental stage (expulsion of the placenta)- After delivery, the uterus continues to contract and shrink, causing the placenta to detach and be expelled.
- A hematoma forms over the uterine placental site to prevent further significant blood loss; mild bleeding persists for 3 to 6 weeks after delivery.
- Uterine involution- The uterus continues to contract and decrease in size for 3 to 6 weeks after delivery; the uterus always remains slightly enlarged over its pregnant size.
Total Weight Gain (Ranges) For Single Fetus
Although pregnancy typically lasts 40 weeks, the range of 38 to 42 weeks is considered full terms.