Pregnancy

The period from conception to birth. Pregnancy begins with the fertilization of an ovum (egg) and its implantation. The egg develops into the placenta and the embryo, which grows to form the fetus. Most eggs implant into the uterus. Very occasionally, an egg implants into an abnormal site, such as a fallopian tube, resulting in an ectopic pregnancy. A normal pregnancy lasts around 40 weeks from the first day of the woman’s last menstrual period. It is divided into 3 stages (trimesters) of 3 months each. For the first 8 weeks of pregnancy, the developing baby is called an embryo; thereafter it is called a fetus. In the 1st trimester the breasts start to swell and may become tender. Morning sickness is common. The baby’s major organs have developed by the end of this stage. During the 2nd trimester, the mother’s nipples enlarge and darken and weight rises rapidly. The baby is usually felt moving by 22 weeks. During the 3rd trimester, stretch marks and colostrum may appear, and Braxton Hick’s contractions may be felt. The baby’s head engages at about 36 weeks. Common, minor health problems during pregnancy include constipation, haemorrhoids, heartburn, pica, swollen ankles, and varicose veins. Other common disorders include urinary tract infections, stress incontinence (see incontinence, urinary), and candidiasis. Complications of pregnancy and disorders that affect it include antepartum haemorrhage; diabetic pregnancy; miscarriage; polyhydramnios; pre-eclampsia; prematurity; and Rhesus incompatibility. (See also childbirth; fetal heart monitoring; pregnancy, multiple.)