Changes of the female reproductive system during pregnancy

Blood volume: blood volume increases gradually by 30 to 50 percent (1500 ml to 3 units). This results in decreased concentration of red blood cells and haemoglobin indicating the need for iron which is so important during pregnancy. By the time pregnancy reaches term, the body has usually compensated for the decrease resulting in a mostly normal blood count. Blood count is interpreted as anemia when the hemoglobin falls below 10.5 grams/100ml and the hematocrit drops below 30%. Increased blood volume compensates for hypertrophied vascular system of an enlarged uterus also improving the placental performance.

Cardiac output: cardiac output increases by about 30 percent during the first and second trimester to accommodate for hyper-volume. This is not a problem for the mother with a normal heart. However, a mother with a heart problem is at risk for cardiac decompensation especially at 28 to 35 weeks of pregnancy when the cardiac load is at its peak due to increased blood volume. This also happens during labour and immediately after delivery when rapid hemodynamic changes occur. The change in heart output is reflected by the heart rate which usually increases by ten beats per minute. Hence, women with a cardiac problem need to be advised to get plenty of rest and to report to an appropriate health facility in case of any shortness of breath or unusual symptoms.

Blood pressure: in a typical situation, the blood pressure of a pregnant mother will not rise. During pregnancy, blood pressure should be checked carefully and often since a significant increase is one of the indicators of toxemia of pregnancy. When monitoring the blood pressure, be sure it is done under the same circumstances always (patient's left arm in sitting position).

Venous return: the lower extremities are often hampered in the last months of pregnancy due to the expanding uterus restricting physical movement and interfering with the return of blood flow. This results in swelling of the feet and legs. Advise the mother to rest frequently to improve venous return and decrease edema. The pregnant women should also be informed to elevate her feet and legs while sitting or lying down. Besides, the women should be advised not to lie in a supine position since this inhibits the return blood flow as the heavy uterus presses on the vessels leading to vena cava syndrome (see figure 4.3) or supine hypotension. The mother may also complain of dizziness, nausea and weakness.