Obstetrics

Obstetrics (from the Latin obstare, "to stand by") is the surgical specialty dealing with the care of a woman and her offspring during pregnancy, childbirth and the puerperium (the period shortly after birth). Almost all modern obstetricians are also gynaecologists; see Obstetrics and gynaecology.

Maternal physiology

During pregnancy, the woman undergoes many physiological changes, which are entirely normal, including cardiovascular, renal, hematologic, metabolic or respiratory changes that become very important in the event of complications.

Related Topics:
Woman - Physiological - Cardiovascular - Renal - Hematologic - Metabolic - Respiratory

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Metabolism

During pregnancy, both protein metabolism and carbohydrate metabolism are affected. One kilogram of extra protein is deposited, with half going to the fetus and placenta, and another half going to uterine contractile proteins, breast glandular tissue, plasma protein, and hemoglobin.

Related Topics:
Protein metabolism - Carbohydrate metabolism - Kilogram - Protein - Fetus - Placenta - Uterine - Breast gland - Hemoglobin

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Nutrition

• Increased caloric requirement by 300 kcal/day
• Gain of 20 to 30 lb (10 to 15 kg)
• Increased protein requirement to 70 or 75 g/day
• Increased folate requirement from 0.4 to 0.8 mg/day (important in preventing neural tube defects)

All patients are advised to take prenatal vitamins to compensate for the increased nutritional requirements.

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Cardiovascular

The woman is the sole provider of nourishment for the embryo and later, the fetus, and so her plasma and blood volume slowly increase by 40-50% over the course of the pregnancy to accommodate the changes. This results in overall vasodilation, an increase in heart rate (15 beats/min more than usual), stroke volume, and cardiac output. Cardiac output increases by ~50%, mostly during the first trimester. The systemic vascular resistance also drops due to the smooth muscle relaxation caused by elevated progesterone, leading to a fall in blood pressure. Diastolic blood pressure consequently decreases between 12-26 weeks, and increases again to prepregnancy levels by 36 weeks. If the blood pressure remains abnormal beyond 36 weeks, the woman should be investigated for pre-eclampsia, a condition that precedes eclampsia.

Related Topics:
Woman - Embryo - Fetus - Plasma - Blood - Vasodilation - Heart rate - Cardiac output - Blood pressure - Pre-eclampsia - Eclampsia

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Pulmonary

• Increased tidal volume (30-40%)
• Decreased total lung capacity (TLC) by 5% due to elevation of diaphragm from uteral compression
• Decreased expiratory reserve volume
• Increased minute ventilation (30-40%) which causes a decrease in PaCO2 and a compensated respiratory alkalosis

All of these changes can contribute to the dyspnea (shortness of breath) that a pregnant woman may experience.

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Hematology

• The plasma volume increases by 50% and the red blood cell volume increases only by 20-30%.
• Consequently, the hematocrit decreases.
• White blood cell count increases and may peak at over 20 mil/mL in stressful conditions.
• Decrease in platelet concentration to a minimal normal values of 100-150 mil/mL
• The pregnant woman also becomes hypercoagulable due to increased liver production of coagulation factors, mainly fibrinogen and factor VIII.

Gastrointestinal

• nausea and vomiting ("morning sickness") due to elevated B-hCG, which should resolve by 14 to 16 weeks
• prolonged gastric empty time
• decreased gastroesophageal sphincter tone, which can lead to acid reflux
• decreased colonic motility, which leads to increased water absorption and constipation

Renal

• Increase in kidney and ureter size
• Increased glomerular filtration rate (GFR) by 50%, which subsides around 20 weeks postpartum
• Decreased BUN (blood urea nitrogen) and creatinine, and glucosuria (due to saturated tubular reabsorption)
• Persistent glucosuria can suggest gestational diabetes
• Increased renin-angiotensin system, causing increased aldosterone levels
• Plasma sodium does not change because this is offset by the increase in GFR

Endocrine

• Increased estrogen, which is mainly produced in the placenta
• Fetal well being is associated with maternal estrogen levels
• Causes an increase in thyroxine-binding globulin (TBG)
• Increased human chorionic gonadotropin (β-hCG), which is produced by the placenta. This maintains progesterone production by the corpus luteum
• Human placental lactogen (hPL) is produced by the placenta and ensures nutrient supply to the fetus. It also causes lipolysis and is an insulin antagonist, which is a diabetogenic effect.
• Increased progesterone production, first by corpus luteum and later by the placenta. Its main course of action is to relax smooth muscle.
• Increased prolactin

Musculoskeleton and dermatology

• Lower back pain due to a shift in gravity
• Increased estrogen can cause spider angiomata and palmar erythema
• Increase melanocyte-stimulating hormone (MSH) can cause hyperpigmentation of nipples, umbilicus, abdominal midline (linea nigra), perineum, and face (melasma or chloasma)

Others

Edema, or swelling, of the feet is common during pregnancy, partly because the enlarging uterus compresses veins and lymphatic drainage from the legs. For the sake of comfort, many pregnant women wear larger shoes or go without. This may have something to do with the origin of the phrase "barefoot and pregnant".

Related Topics:
Edema - Barefoot and pregnant

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