Blueprints - Pregnancy and Prenatal Care

Question 1

What are the signs and symptoms of pregnancy?

Answer 1

• Signs
  
  • Bluish discoloration of vagina and the cervix (Chadwick sign)
  • Softening and cyanosis of the cervix at or after 4 weeks (Goodell sign)
  • Softening of the uterus after 6 weeks (Ladin sign)
  • Breast swelling and tenderness
  • Development of the linea nigra from umbilicus to pubis
  • Telengiectasias
  • Palmar erythema
• Symptoms
  
  • Amenorrhea
  • Nausea and vomiting
  • Breast pain
  • Quickening - fetal movement

Question 2

What are the diagnostic tools to ascertain pregnancy?

Answer 2

• Laboratory
  
  • Urine test and the hospital laboratory serum assays test for the beta subunit of human chorionic gonadotropin
• Imaging
  
  • A viable pregnancy can be confirmed by ultrasound, which may show the gestational sac as early as 5 weeks on a transvaginal ultrasound or at a beta-hCG of 1,500 to 2,000 mlU/ml.
  • Fetal heart motion may be seen on transvaginal ultrasound as soon as 6 weeks or at a beta-hCG 5000 to 6000 mlU/mL.

Question 3

Define an embryo

Answer 3

• From the time of fertilization until the pregnancy is 8 weeks along (10 weeks’ gestational age [GA]), the conecptus is called an embryo.
  
  • After 8 weeks until the time of birth - it is designated a fetus
    
    • The term infant is used for the period between delivery and 1 year of age.

Question 4

What is the first trimester?

Answer 4

• Lasts until 12 weeks but is also defined as up to 14 weeks GA

Question 5

What is the second trimester?

Answer 5

• Lasts from 12 to 14 until 24 to 28 weeks’ GA

Question 6

What is the third trimester?

Answer 6

• Lasts from 24 to 28 weeks until delivery.

Question 7

What do the terms previable, preterm, term and postterm mean?

Answer 7

• An infant delivered prior to 24 weeks is considered to be previable
• Delivery between 24 to 37 weeks is considered preterm
• Between 37 and 42 weeks is considered term
• A pregnancy carried beyond 42 weeks is considered postterm

Question 8

What do the terms gravidity and parity refer to?

Answer 8

• Gravidity refers to the number of times a woman has been pregnant
  
  • Parity refers to the number of pregnancies that led to a birth at or beyond 20 weeks’ GA or of an infant weighing more than 500g.
    
    • Grand multip refers to a woman whose parity is greater than or equal to 5.

Question 9

What is the gestational age?

Answer 9

• The GA of a fetus is the age in weeks and days measured from the last menstrual period

Question 10

What is developmental age?

Answer 10

• The number of weeks and days since fertilization
  
  • Because fertilization usually occurs about 14 days after the first day of the prior menstrual period, the GA is usually 2 weeks more than the DA.

Question 11

What is the Nagele rule?

Answer 11

• Used to calculate the estimated date of confinement or estimated date of delivery
  
  • subtract 3 months from the LMP (last menstrual period) and add 7 days.

Question 12

What cardiovascular physiological changes occur in pregnancy?

Answer 12

• During pregnancy
  
  • cardiac output increases by 30-50%
    
    • Most increases occur during the first trimester with the maximum being reached between 20 and 24 weeks’ gestation and maintained until delivery.
      
      • The increase in cardiac output is first due to an increase in stroke volume and is then maintained by an increase in heart rate as the stroke volume decreases to near pre-pregnancy levels by the end of the third trimester.
  • Systemic vascular resistance decreases during pregnancy, resulting in a fall in arterial blood pressure
    
    • This decrease is most likely due to elevated progesterone, leading to smooth muscle relaxation
      
      • Between 24 weeks’ gestation and term - the BP slowly returns to pre-pregnancy levels but should never exceed them.

Question 13

What pulmonary change occur during pregnancy?

Answer 13

• There is an increase of 30-40% in tidal volume during pregnancy despite the fact that the total lung capacity is decreased by 5% due to elevation of the diaphragm
  
  • The increases in tidal volume decreases the expiratory reserve volume by about 20%.
    
    • This increase in V(t) with a constant respiratory rate leads to an increase in alveolar and arterial partial pressure oxygen levels and a decrease in PACO2 and PaCO2 levels.
• Partial pressure of carbon dioxide decreases to approx. 30 mm Hg by 20 weeks’ gestation from 40 mm Hg during pre-pregnancy
  
  • The change is likely caused by elevated progesterone levels that either increase the respiratory system’s responsiveness to carbon dioxide or act as primary stimulant.
    
    • This gradient facilitates oxygen delivery to the fetus and carbon dioxde removal from the fetus.
      
      • Dyspnea of pregnancy occurs in 60-70% of patients
        
        • This is possibly secondary to decreased PaCO2 levels, increased V(t) or decreased TLC.

Question 14

What are the gastrointestinal changes that occur during pregnancy?

Answer 14

• Nausea and vomiting occur in more than 70% of pregnancies
  
  • This has been termed morning sickness even though it can occur throughout the day
    
    • These symptoms have been attributed to the elevation in estrogen, progesterone and hCG.
      
      • They may also be due to hypoglycemia and can be treated with frequent snacking.
  • The nausea and vomiting typically resolve by 14-16 weeks’ gestation.
  • Hyperemesis gravidarum refers to a severe form of morning sickness associated with weight loss and ketosis
• During pregnancy
  
  • The stomach has prolonged gastric emptying times and the gastroesophageal sphincter has decreased tone
    
    • Together, these changes lead to reflux and possibily combine with decreased esophageal tone to cause ptylaism or spitting during pregnancy.
  • The large bowel also has decreased motility, which leads to increased water absorption and constipation

Question 15

What are the changes in renal physiology that occur during pregnancy?

Answer 15

• The kidneys increase in size and the urters dilate during pregnancy, which may lead to increased rates of pyelonephritis
  
  • The GFR increases by 50% early in pregnancy and is maintained until delivery.
    
    • As a result of increased GFR, blood urea nitrogen and creatinine decrease by about 25%.
    • An increase in renin-angiotensin system leads to increased levels of aldosterone which results in increased sodium resorption.
  • However, plasma levels of sodium do not increase because of the simultaneous increase in GFR.

Question 16

What are the hematological changes that occur in pregnancy?

Answer 16

• The plasma volume increases by 50% in pregnancy, the RBC volume increases by only 20-30% - leads to a decrease in hematocrit or dilutional anaemia
• The WBC count increases during pregnancy to a mean of 10.5 million/mL with a range of 6-16 million.
  
  • During labour, stress may cause the WBC count to rise over 20 million/mL
• There is a slight decrease in concentration of platelets probably secondary to an increased plasma volume and an increase in peripheral destruction
• Pregnancy is considered to be a hypercoagulable state with an increase in the number of thromboembolic events
  
  • There are elevations in the levels of fibrinogen and factors VII-X.
    
    • However, the actual clotting and bleeding times do not change
      
      • The increased rate of thromboembolic events in pregnancy may also be secondary to the other elements in Virchow’s traid - that is an increase in venous stasis and vessel endothelial damage.

Question 17

What happens ot estrogen in pregnancy?

Answer 17

• Pregnancy is a hyperestrogenic state.
• The increased estrogen is produced primarily by the placenta, with the ovaries contributing to a lesser degree.
  
  • Unlike estrogen production in the ovaries, where estrogen precursors are produced in ovarian theca cells and transferred to the ovarian granulosa cells
    
    • Estrogen in the placenta is derived from the circulating plasma borne precursors produced by the maternal adrenal glands
  • Fetal well being has been correlated with maternal serum estrogen levels, with low estrogen levels being associated with conditions such as fetal death and anencphaly

Question 18

What happens to hCG during pregnancy?

Answer 18

• The hormone hCG is composed of two dissimilar alpha and beta subunits
  
  • The alpha subunit of hCG is identical to the alpha subunits of LH, FSH and TSH where the beta subunits differ.
• Levels of hCG double approximately every 48 hours during early pregnancy, reaching a peak approximately 10-12 weeks, and thereafter declining to reach a steady state after week 15.
• The placenta produces hCG which acts to maintain the corpus luteum in early pregnancy.
  
  • The corpus luteum produces progesterone which maintains the endometrium
• Eventually, the placenta takes over progesterone production and the corpus luteum degrades into the corpus albicans.
• Progesterone levels increase over the course of pregnancy.
  
  • Progesterone causes relaxation of the smooth muscle which has multiple effects on the gastrointestinal, cardiovascular and genitourinary systems.

Question 19

What is the function of human placental lactogen?

Answer 19

• HPL is produced in the placenta and is important for ensuring a constant nutrient supply to the fetus.
  
  • hPL also known as human chorionic somatomammotropin (hCS), induces lipolysis with a concomitant increase in circulating free fatty acids, hPL also acts as an insulin antagonist, along with various other placental hormones
    
    • has a diabetogenic effect
      
      • This leads to increased levels of insulin and protein synthesis
        
        • Levels of prolactin are markedly increased during pregnancy
          
          • These levels decrease after delivery but later increase in response to suckling.

Question 20

What happens to thyroid hormones during pregnancy?

Answer 20

• There are two major changes in thyroid hormones during pregnancy
  
  • First, estrogen stimulates thyroid binding globulin, leading to an elevation in total T3 and T4 but free T3 and T4 remain relatively constant
  • Second, hCG has a weak stimulating effect on the thyroid, likely because its alpha sub group is similar to TSH
    
    • This leads to a slight increase in T3 and T4 and a slight decrease in TSH early in pregnancy.
  • Overall, however pregnancy is considered a euthyroid state.

Question 21

What are the musculoskeletal and dermatological changes during pregnancy?

Answer 21

• The obvious change in the center of gravity during pregnancy can lead to a shift in posture and lower back pain which worsens throughout pregnancy, particularly during the third trimester
• Numerous changes occur in the skin, including spider angiomata, palmar erythema secondary to increased estrogen levels:
  
  • spider angiomata
  • palmar erythema secondary to increased estrogen levels
  • hyperpigmentation of the nipples, umbilicus, abdominal midline (linea nigra), perineum and face (melasma or chloasma) secondary to increased levels of the melanocyte stimulating hormones and the steroid hormones
• Pregnancy also asssociated with carpal tunnel syndrome - results from compression of the median nerve - the incidence in pregnancy varies greatly and symptoms are usually self-limited.