- Oestrogen and progesterone are the chief pregnancy hormones.
- High levels of progesterone cause some internal structures to increase in size, including the uterus which changes from the size of a small pear in its non-pregnant state to five times its normal size at full term.
- The expected increase in weight of the mother in an average pregnancy is 9-12 kg.
- A higher circulating blood volume is required to provide extra blood flow through the placenta to the fetus, and the mother also produces more red blood cells.
- The increase in blood volume exceeds the increase in red blood cells, so they are diluted in the much larger volume of blood plasma, causing physiological anaemia. This is one reason why iron supplementation is so important in pregnancy.
- Lower blood pressure is particularly common in early pregnancy because progesterone causes a slight relaxation in the blood vessels. This can cause dizziness and perhaps even a brief loss of consciousness.
- A reduction in blood flow back to the heart may lead to oedema — swelling due to fluid collecting in the legs and feet.
- During pregnancy, many women get short of breath because the growing baby crowds the mother’s lungs and she has less room to breathe. She may also experience indigestion as her stomach is pushed higher.
- During pregnancy, the muscles in the walls of the gastrointestinal system relax slightly, and the rate at which food moves along the gut is slowed down. This maximises the absorption of nutrients into the mother’s blood, which is good for the fetus, but the mother may also experience nausea or constipation.
- Needing to urinate often is normal, especially in the first and last months of pregnancy, because the growing uterus presses against the bladder. At night, the bladder fills more quickly as fluid (oedema) that collected in the legs during the day is re-absorbed.
- Changes in the woman’s hormones, and mechanical stretching of her growing abdomen and breasts, can cause stretch marks in the skin of these areas during pregnancy. Other skin changes may include brown pigmentation and increased sweating.
- In the second trimester, the breasts begin to produce colostrum — a yellowish secretion that thickens as pregnancy progresses. It is rich in proteins and maternal antibodies, and should always be fed to newborn babies.
What causes back pain in pregnant women?
Back pain is common in pregnant women because their posture changes to accommodate the weight of the growing uterus. The back curves inwards and the belly curves outwards, putting strain on the back, which can cause pain.
A pregnant woman gained 2 kg in the first 20 weeks of pregnancy, then 0.5 kg a week for the next 10 weeks, then 0.1 kg for the last 10 weeks. What is her total weight gain at full term? What does this suggest might be happening?
This woman’s weight gain was normal for the first 30 weeks of her pregnancy: she gained 2 kg in the first 20 weeks and 0.5 kg every week for the next ten weeks. However, she would be expected to gain 0.5 kg every week from 30-40 weeks, but her weight gain slowed down to 0.1 kg per week in this period. It is not possible to tell whether this slow weight gain near the end of pregnancy is a sign that the fetus is not developing normally, but it should certainly be investigated at a health facility. Some women have normal pregnancies without gaining much weight, but in others it is a sign of intrauterine growth restriction (IUGR) of the fetus.
Why is it important for pregnant women to have more iron-rich foods in their diet, or take iron tablets?
Pregnant women normally experience mild physiological anaemia because their blood volume increases faster than the rise in the number of red blood cells in their circulation. Iron is required for the production of haemoglobin, the oxygen-carrying substance in red blood cells. If a woman doesn’t have enough iron in her body, she won’t be able to make enough red blood cells, so her anaemia could become serious. Eating a diet containing plenty of iron-rich foods, or taking iron tablets, helps her to make enough red blood cells to carry the oxygen she and her growing fetus need.
What could happen to a pregnant woman if she is lying on her back? Explain your answer.
If a pregnant woman is lying on her back, the weight of her uterus presses down on the major blood vessel (the vena cava) returning blood from her body to her heart. This in turn leads to less blood being pumped out of her heart to the rest of her body, so her blood pressure drops suddenly. She may experience dizziness, or even a loss of consciousness, because not enough oxygen is reaching her brain.
What information might help you to make a decision on the need for medical advice when a pregnant woman has shortness of breath?
Shortness of breath is common in pregnancy as the uterus grows and crowds the mother’s lungs, so she has less room in which to breathe. But if she is also weak, tired and short of breath all the time, you should refer her to seek medical advice. She could be anaemic, or have heart problems, or possibly her diet is poor.
Which of the following statements is false? In each case, say why it is incorrect.
A Lying flat after a meal is recommended for pregnant women because it helps digestion.
B Frequent urination in late pregnancy is normal because the uterus pushes down on the bladder.
C Heart rate, stroke volume and cardiac output all increase during pregnancy.
D Oedema in pregnancy gets worse during the night.
E Pigmentation may appear on the face, or as a dark line on the abdomen in some pregnant women.
F Colostrum should not be fed to newborn babies.
G Progesterone causes the uterus to increase in size to accommodate the growing fetus.
A is false. Lying flat after a meal is not recommended in pregnancy and it does not help digestion. The contents of the pregnant woman’s stomach will be pushed upwards into her oesophagus in her chest if she is lying down, and the acids that digest her food can cause a burning sensation known as ‘heartburn’.
B is true. Frequent urination in late pregnancy is normal because the uterus pushes down on the bladder and it can hold less urine.
C is true. Heart rate, stroke volume and cardiac output all increase during pregnancy, because the woman’s larger body, uterus and the fetus all need a larger blood flow to provide them with nutrients and oxygen.
D is false. Oedema in pregnancy usually improves during the night. The fluids that collect in the woman’s legs during the daytime are absorbed into her blood stream when her legs are raised in bed at night.
E is true. Pigmentation may appear on the face, or as a dark line on the abdomen in some pregnant women.
F is false. Colostrum should always be fed to newborn babies. It is rich in proteins and contains the mother’s antibodies, which help to protect the baby from infection.
G is true. Progesterone causes the uterus to increase in size to accommodate the growing fetus.