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Normal Values in Pregnancy

WHEC Practice Bulletin and Clinical Management Guidelines for healthcare providers. Educational grant provided by Women's Health and Education Center (WHEC).

The physiologic, biochemical, and anatomic changes that occur during pregnancy are extensive and may be systemic or local. However, most systems return to pre-pregnancy status between the time of delivery and 6 weeks postpartum. Major adaptation in maternal anatomy, physiology, and metabolism are required for a successful pregnancy. Hormonal changes, initiated before conception, significantly alter maternal physiology, and persist through both pregnancy and initial postpartum period. A full understanding of physiologic changes is necessary to differentiate between normal alterations and those that are abnormal. This document describes maternal adaptations in pregnancy. An understanding of the normal physiologic changes and values induced by pregnancy is essential in understanding coincidental disease processes. Many laboratory values are dramatically altered from non-pregnant values. We hope this provides a valuable tool to manage your patients effectively.

I. Cardiac Invasive Monitoring:

Cardiac output is increased in pregnancy but is essentially unchanged over the course of pregnancy. Heart rate gradually rises 5 to 10 beats per minute over the course of pregnancy. Cardiac output (CO) is the product of stroke volume (SV) and heart rate (HR) (CO = SV X HR), both of which increase during pregnancy and contribute to the overall rise in CO.

Measure

Value (36-38 weeks)

Units

Cardiac output (CO)

6.2 1.0

liters/minute

Systemic vascular resistance (SVR)

1,210 266

dyne cm second-5

Heart rate

83 10

beats/minute

Pulmonary vascular resistance

78 22

dyne cm second-5

Colloid oncotic pressure

18.0 1.5

mm Hg

Mean arterial pressure (MAP)

90.3 5.8

mm Hg

Pulmonary capillary wedge pressure (PCWP)

7.5 1.8

mm Hg

Central venous pressure (CVP)

3.6 2.5

mm Hg

Left ventricular stroke work index

48 6

g mm

II. Cardiac Non-invasive Monitoring:

Maternal hemodynamics refers to the relationships between blood pressure, cardiac output, and vascular resistance. Blood pressure is measured by auscultation, use of an automated cuff, or directly with an intra-arterial catheter. Cardiac output (CO) is measured by dilutional techniques requiring central venous access, by Doppler or two-dimensional echocardiographic techniques, or by electrical impedance. Peripheral resistance is calculated using Ohm's law: TPR = MAP X 80/CO; where TPR is total peripheral resistance (dyne.sec.cm-5), MAP is mean arterial pressure (millimeters of mercury [mm Hg]), and CO is cardiac output (L/min).

Measure

10-18 weeks

18-26 weeks

26-34 weeks

34-42 weeks

Cardiac output (L/min)

7.26 1.56

7.60 1.63

7.38 1.63

6.37 1.48

Stroke volume (mL)

85 21

85 21

82 21

70 14

SVR (dyne cm second)

966 226

901 224

932 240

1,118 325

Heart rate (beats/min)

87 14

90 14

92 14

92 7

Mean arterial pressure (mm Hg)

87 7

84 7

84 7

86 7

III. Third-Trimester Arterial Blood Gas Values:

Increasing progesterone levels drive a state of chronic hyperventilation, as reflected by a 30 to 50% increase in tidal volume by 8 weeks' gestation. Chronic mild hyperventilation results in increased alveolar oxygen (PAo2) and decreased arterial carbon dioxide (Paco2) from normal levels of 37 to 40 mm Hg to 27 to 32 mm Hg. The drop in Paco2 is especially critical, because it drives a more favorable carbon dioxide (CO2) gradient between the fetus and mother, facilitating CO2 transfer. The low maternal Paco2 results in a chronic respiratory alkalosis. The base values in normal pregnancy at normal and moderate altitude:

Measure

Normal Altitude

Moderate Altitude (1,388 M, PROVO, UT)

Arterial pH

7.44 0.04

7.46 0.02

Arterial Po2

85 5

86.2 7.3

O2 Saturation (%)

 

96 1

Arterial Pco2 (mm Hg)

29.7 2.8

26.6 2.7

Sodium bicarbonate (mEq/L)

22.0 2.1

18.6 1.9

IV. Pulmonary Function Tests:

Increased tidal volume results in an overall parallel rise in minute ventilation, despite a stable respiratory rate. (Minute ventilation = Tidal volume X Respiratory rate). During pregnancy, the mucosa of the nasopharynx becomes hyperemic and edematous with hypersecretion of mucous due to increased estrogen. These changes often lead to marked nasal stuffiness; epistaxis is also common. Placement of nasogastric tubes may cause excessive bleeding if adequate lubrication is not used. Polyposis of the nose and nasal sinuses develops in some individuals but regresses in postpartum period. Because of these changes, many gravid women complain of chronic cold symptoms. However, the temptation to use nasal decongestants should be avoided because of risk of hypertension and rebound congestion.

Measure

8-11 Weeks

20-23 Weeks

28-31 Weeks

36-40 Weeks

Respiratory Rate (br/min)

15 (14-20)

16 (15-18)

18 (15-20)

17 (16-18)

Tidal Volume (mL)

640 (550-710)

650 (625-725)

650 (575-720)

700 (660-755)

Peak Flows (5th% Shown as Lower Limit of Normal) Stable Over Gestation:

Measure

Peak Flow (L/Min)

Standing

>320

Sitting

>310

Supine

>300

Mean Values:

Vital Capacity:
First Trimester
Second Trimester
Third Trimester

 
3.8
3.9
4.1

 
Liters
Liters
Liters

Inspiratory Capacity:
First Trimester
Second Trimester
Third Trimester

 
2.6
2.7
2.9

 
Liters
Liters
Liters

Expiratory Reserve Volume:
First Trimester
Second Trimester
Third Trimester

 
1.2
1.2
1.2

 
Liters
Liters
Liters

Residual Volume:
First Trimester
Second Trimester
Third Trimester

 
1.2
1.1
1.0

 
Liters
Liters
Liters

V. Liver Function Tests:

The size and histology of the liver are unchanged in pregnancy. However, many clinical and laboratory signs usually associated with liver disease are present. Spider angiomas and palmar erythema, caused by elevated estrogen levels, are normal and disappear, soon after delivery. The serum albumin and total protein levels fall progressively during gestation. By term, albumin levels are 25% lower than non-pregnant levels. Despite an overall increase in total body protein, decreases in total protein and albumin concentrations occur as a result of hemodilution.

Measure

Week 12

Week 32

Intrapartum

Total alkaline phosphatase (IU/L)

42 (17-88)

82 (46-165)

97 (48-249)

Gamma glutamyl transferase (IU/L)

7 (2-18)

6 (3-20)

9 (5-79)

Aspartate transaminases (AST, IU/L)

9 (4-18)

9 (5-21)

11 (5-103)

Alanine transaminases (ALT, IU/L)

9 (4-30)

8 (2-22)

12 (5-115)

Total bilirubin (IU/L)

4 (2-10)

4 (2-9)

4 (2-10)

VI. Electrolytes, Osmolality, and Renal Function:

The increase in total body water of 6.5 to 8.5L by the end of gestation represents one of the most significant adaptations of pregnancy. The water content of the fetus, placenta, and amniotic fluid at term accounts for about 3.5L. Additional water is accounted for by expansion of volume by 1,200 to 1,300 ml, and red blood cells by 300 to 400 ml. The remainder is attributed to extravascular fluid, intracellular fluid in the uterus and breasts, and expanded adipose tissue. Expansion in plasma volume begins shortly after conception, partially mediated by a change in maternal osmoregulation through altered secretion of arginine vasopressin (AVP) by the posterior pituitary. Water retention exceeds sodium retention; although an additional 900 mEq of sodium decrease by 3 to 4 mmol/L. Renal plasma flow (RPF) increases markedly from early in gestation and may actually initially begin to increase during luteal phase before implantation. RPF rises 75% over non-pregnant levels by 16 weeks' gestation. The increase is maintained until 34 weeks' gestation, when a decline in RPF of 25% occurs. Like RPF, glomerular filtration rate (GFR) as measured by inulin clearance increases by 5 to 7 weeks. By the end of the first trimester, GFR is 50% higher than in non-pregnant state, and this is maintained until the end of the pregnancy. The creatinine clearance in pregnancy is greatly increased to values of 150 to 200 ml/min (normal: 120 ml/min). As with GFR, the increase in creatinine clearance occurs by 5 to 7 weeks' gestation, and normally is maintained until the third trimester.

Measure

12 Weeks

20 Weeks

28 Weeks

38 Weeks

Total osmolality (mosmol/kg)

267-279

269-285

273-283

271-289

Sodium (mmol/L)

133-141

136-142

135-143

135-141

Potassium (mmol/L)

3.5-4.3

3.5-4.3

3.5-4.4

3.6-4.5

Chloride (mmol/L)

102-108

103-111

104-112

102-111

Creatinine clearance (ml/24 hours)

76-188

88-168

40-192

52-208

Blood urea nitrogen (BUN)

1.7-4.4

1.9-5.3

1.9-4.2

1.8-4.6

Serum albumin (g/L)

37-47

34-42

31-42

31-39

Urine volume (mL/24 hours

750-2,500

850-2,400

750-2,700

550-3,900

5th -- 95th percentile

24-Hour Urinary Protein (mg/24 Hours) Mean SD:

First Trimester

80.0 60.6

Second Trimester

116.7 69.3

Third Trimester

115.3 69.2

VII. Metabolic Markers and Lipids:

Amino acids are actively transported across the placenta, where they are used by the fetus for protein synthesis and as an energy source. In late pregnancy, the fetoplacental unit contains approximately 500 mg of protein. During pregnancy, fat stores are preferentially used as a substrate for fuel metabolism, and thus, protein catabolism is decreased. Plasma lipids and lipoproteins increase in pregnancy. A gradual two- to three-fold rise in triglyceride levels occurs by term and levels of 200 to 300 mg/dl are normal. Triglyceride concentrations return to normal by 8 weeks' postpartum even with lactation, but cholesterol and low-density lipoprotein levels remains elevated. The mechanisms for the pregnancy-induced changes in lipids are not completely understood, but appear to be partly caused by the elevated levels of estrogen, progesterone, and human placenta lactogen (hPL).

Measure

4-16 Weeks

16-24 Weeks

24-34 Weeks

Term

Uric acid (mg/dL)

3.21 0.10

3.48 0.13

3.49 0.11

4.72 0.13

Creatinine (mg/dL)

0.58 0.03

0.50 0.04

0.50 0.03

0.57 0.03

Total cholesterol (mg/dL)

153.5 3.8

194.0 5.2

218.3 6.4

220.4 8.4

Triglycerides

70.1 4.5

109.6 5.8

139.6 6.9

159.0 8.1

Free fatty acids (mEq/L)

0.42 0.03

0.34 0.02

0.21 0.02

0.67 0.04

Medians SD

VIII. Hematologic Indices:

Maternal blood volume begins to increase at about 6 weeks' gestation. Therefore, it increases progressively until 30 to 34 weeks and then plateaus until delivery. The average expansion of blood volume is 40 to 50%, although individual increases range from 20 to 100%. Women with multiple pregnancies have a larger increase in blood volume than those with singletons. The increase in blood volume results from a combined expansion of both plasma volume and red blood cell (RBC) mass. The peripheral white blood cell (WBC) count rises progressively during pregnancy. The traditional view of the immunologic system in pregnancy is that the fetus is a semi-allograft and a successful pregnancy is dependent on either evasion of immune surveillance or suppression of the maternal adaptive immune response.

Red Blood Cell (RBC) Indices in Iron-Treated Women (66 mg Elemental Iron as Fumarate):

Red blood cell count (1012/L)
First trimester
Second trimester
Third trimester
Term

 
>3.45
>3.29
>3.23
>3.54

MCV, fl, 5th -95th percentile
First trimester
Second trimester
Third trimester
Term

 
88-101
89-104
90-104
90-102

Hemoglobin (g/dL)
First trimester
Second trimester
Third trimester
Term

 
>11.1
>10.64
>10.47
>11.5

MCH, pg
First trimester
Second trimester
Third trimester
Term

 
>30.1
>29.9
>30.2
>30.1

Hematocrit (%)
First trimester
Second trimester
Third trimester
Term

 
>33
>32
>31
>34

MCHC, g/dL
First trimester
Second trimester
Third trimester
Term

 
>32.6
>31.7
>32.2
>31.9

First trimester: 9-13 weeks; Second trimester: 19-22 weeks; Third trimester: 31-34 weeks; Term: 39-43 weeks. Mean cell volume (MCV); Mean corpuscular hemoglobin (MCH); Mean cell hemoglobin concentration (MCHC)
<5th percentile shown as lower limit of normal.

Platelet Count (109/L):

First trimester (12 weeks)

240 (170-310)

Third trimester (28 weeks)

250 (150-360)

Term (38 weeks)

240 (140-370)

Median (5th- 95th percentile)

White Blood Cell (WBC) Count (109/L)

18 Weeks

8.8 (5.6-13.8)

32 Weeks

9.7 (6.0-15.7)

39 Weeks

9.4 (5.8-15.1)

Mean 1.96 x SD

Iron, Folate, and Vitamin B12 Levels:

Mean Ferritin (ug/L)
First trimester
Third trimester
Term

 
46.8 2.5
20.8 1.3
21.7 1.6

Mean TIBC (umol/L)
First trimester
Third trimester
Term

 
59.3 0.6
73.8 0.9
77.7 0.9

Folate (umol/L)
First trimester
Third trimester
Term

 
6.7 0.3
6.4 0.3
6.9 0.4

Vitamin B12
First trimester
Third trimester
Term

 
345.6 8.9
259.3 6.0
241.8 6.5

First trimester: mean 12.6 weeks; Third trimester: 32 weeks; Term: 38 weeks
Total Iron Binding Capacity (TIBC)

Fasting Homocysteine With and Without Folic Acid Supplementation (Various Doses) (umol/L):

Measure

8 Weeks

20 Weeks

32 Weeks

Unsupplemented

6.48 1.30

5.22 1.29

5.16 1.32

Supplemented

6.32 1.34

4.18 1.32

4.42 1.37

Means 1 SD

IX. Coagulation Factors and Parameters:

Pregnancy places women at a 5 to 6 fold increased risk for thromboembolic disease. This greater risk is caused by increased venous stasis, vessel wall injury, and changes in the coagulation cascade that leads to hypercoagulability. In pregnancy, several procoagulant coagulation factors are increased, and changes occur to some of the natural inhibitors of coagulation. In addition, pregnancy causes a decrease in the fibrinolytic system with reduced levels of available circulating plasminogen activator inhibitor (PAI-1). These physiologic changes provide defense against peripartum hemorrhage.

Coagulation Factors:

Measure

11-15 Weeks

21-25 Weeks

31-35 Weeks

36-40 Weeks

Factor VII

111 (60-206)

150 (80-280)

162 (84-312)

171 (87-336)

Factor X

103 (62-169)

115 (74-177)

123 (78-194)

127 (72-208)

Factor V

93 (46-188)

82 (66-185)

82 (34-195)

85 (39-184)

Factor II

125 (70-224)

125 (73-214)

115 (74-179)

115 (68-194)

(% of standards shown, mean and range)

Coagulation Parameter in Normal Pregnancy and Puerperium (n = 117):

Measure

10 Weeks

20 Weeks

30 Weeks

36 Weeks

INR

0.97 0.08

0.91 0.06

0.88 0.07

0.87 0.07

PTT (sec)

27.0 2.7

26.9 2.7

27.1 2.9

27.5 2.8

Fibrinogen (mg %)

412.5 69.5

463.9 83.9

538.8 107.3

556.9 113.3

Antithrombin III

101.5 12.7

101.4 10.3

104.2 12.5

102.8 13.5

Protein C (%)

99.4 21.3

107.5 24.9

99.3 26.0

94.9 25.5

Protein S (%)

64.1 15.8

62.1 14.2

54.0 13.3

51.7 17.9

PAI (AU/ml)

10.3 4.7

11.3 5.0

20.5 7.3

22.4 7.5

International Normalized Ratio (INR); Plasminogen Activator Inhibitor (PAI); Partial Thromboplastin Time (PTT).
Mean SD

X. Endocrine Changes and Parameters:

Thyroid diseases are common in women of childbearing age. However, normal pregnancy symptoms mirror those of thyroid disease, making it difficult to know when screening for thyroid disease is appropriate. In addition, the physiologic effects of pregnancy frequently make the interpretation of thyroid tests difficult. Therefore, it is important for obstetrician to be familiar with the normal changes in thyroid function that occur during pregnancy.

TSH (mIU/L) and Free T4 (ng/dL) by Race (means, IQ range):

Measure

Black

White

First Trimester
TSH
Free T4

 
0.9 (0.4-1.6)
1.0 (0.9-1.1)

 
1.3 (0.8-2.0)
1.0 (0.9-1.1)

Second Trimester
TSH
Free T4

 
1.0 (0.6-1.5)
0.9 (0.8-1.0)

 
1.6 (1.0-2.2)
0.9 (0.8-1.0)

Third Trimester
TSH
Free T4

 
1.2 (0.9-1.9)
0.8 (0.7-0.9)

 
1.5 (1.4-2.1)
0.8 (0.7-0.9)

Delivery
TSH
Free T4

 
2.1 (1.3-3.1)
0.8 (0.7-0.9)

 
2.8 (2.0-4.4)
0.8 (0.7-0.9)

Screening and Diagnostic Thresholds across Pregnancy. TSH >2.5 mIU/L -- requires further workup for hypothyroidism. Total T4 <100 nmol/L (7.8 /dL) -- diagnostic of hypothyroidism. Thyroxine (T4); Thyroid-Stimulating Hormone (TSH).

Sequential Measurements of Plasma CRH, ACTH, Cortisol, Aldosterone and Urinary Free Cortisol during Pregnancy:

Weeks of Gestation

CRH

(PG/ML)

ACTH

(PG/ML)

Cortisol

(G/DL)

DHEAS

(/DL)

Aldosterone

(PG/ML)

Urinary Free Cortisol

(G/24 H)

11-15

115 56

8.8 2.8

10.5 1.4

102 14

412 63.6

54.8 7.3

21-25

145 30

9.8 1.5

20.0 1.1

85.1 9.0

487 42.8

84.4 8.4

31-35

1,570 349

12.1 2.0

22.0 1.2

62.6 6.8

766 94

105 8.8

36-40

4,346 754

18.6 2.6

26.0 1.1

63.8 7.1

1,150 170

111 8.7

Adrenocorticotrophic Hormone (ACTH); Corticotrophin-releasing Hormone (CRH); Dehydroepiandrosterone (DHEAS).

Calcium Metabolism:

Measure

13-16 Weeks

21-24 Weeks

29-32 Weeks

>37 Weeks

Total Calcium (mmol/L)

2.25-2.35

2.15-2.30

2.10-2.25

2.05-2.25

Ionized Calcium (mmol/L)

1.10-1.20

1.05-1.20

1.10-1.15

1.05-1.15

( 1 SD)

Measure

8-11 Weeks

20-23 Weeks

28-31 Weeks

>37 Weeks

Calcitonin (ng/L)

73-101

79-108

87-113

83-109

Parathyroid hormone (ng/L)

7-15

4.5-12

5-15

10-17

1,25 Dihydroxy Vitamin D (ng/L)

58-78

94-122

98-136

94-150

XI. Umbilical Cord Blood / Fetal Physiology:

The fetus develops within a complex milieu and is wholly dependent on its mother for nutrients. Pregnancy-associated cardiovascular changes include a doubling of maternal cardiac output and a 40% increase in blood volume. Uterine blood flow at term averages 750 ml/min, or 10 to 15% in maternal cardiac output. Normal term placental weight averages 450 g, representing approximately one seventh (one sixth with cord and membranes) of fetal weight. Mean amniotic fluid volume increases from 250 to 800 ml between 16 and 32 weeks, and decreases to 500 ml at term. Fetal urine production ranges from 400 to 1,200 ml/day and is the primary source of amniotic fluid. The fetal umbilical circulation receives approximately 40% of fetal combined ventricular output (300 ml/mg/min). Umbilical blood flow is 70 to 130 ml/min after 30 weeks' gestation. Fetal cardiac output is constant over a heart rate range of 120 to 180 bpm. The fetus exists in a state of aerobic metabolism, with arterial Po2 values in the 20- to 25- mm Hg range. Approximately 20% of the fetal O2 consumption of 8 ml/kg/min is required in the acquisition of new tissue. The maternal environment during pregnancy (e.g., under-nutrition) may have significant long-term effects, because growth-restricted offspring demonstrate an increased risk of adult metabolic syndrome.

Umbilical Cord Blood at Delivery:

Measure

Artery

Vein

pH

7.06 -- 7.36

7.14 -- 7.45

Pco2 (mm Hg)

27.8 -- 68.3

24.0 -- 56.3

Po2 (mm Hg)

9.8 -- 41.2

12.3 -- 45.0

Base deficit (mmol/L)

0.5 -- 15.3

0.07 -- 12.6

White blood cell count (109/L)

11.1 -- 16.2

Red cell count (1012/L)

4.13 -- 4.62

Hemoglobin (g/dL)

15.3 -- 17.2

Hematocrit (%)

45.2 -- 50.9

MCV (fl)

107.4 -- 113.3

Platelet count (109/L)

237 -- 321

Reticulocyte count (109/L)

145.8 -- 192.6

25th -- 75th percentile

Summary:

A complete understanding of physiologic changes allows each obstetrician to provide a more thorough explanation for various changes and symptoms. Plasma osmolality decreases during pregnancy as a result of a reduction in the serum concentration of sodium and associated anions. The osmolality set point for arginine vasopressin (AVP) release and thirst is also decreased. Cardiac output (CO) increases 30 to 50 percent during pregnancy. Supine positioning and standing are both associated with a fall in CO. Cardiac output (CO) is maximal during labor and the immediate postpartum period. As a result of the marked fall in systemic vascular resistance and pulmonary vascular resistance, pulmonary capillary wedge pressure (PCWP) does not rise, despite an increase in blood volume. Maternal blood pressure (BP) decreases early in pregnancy. The diastolic BP and the mean arterial pressure nadir at mid-pregnancy (16 to 20 weeks) and return to pre-pregnancy levels at term. Pao2 and Paco2 fall during pregnancy secondary to increased minute ventilation. This facilitates transfer of CO2 from the fetus to the mother and results in a mild respiratory alkalosis. Maternal plasma volume increases 50 percent during pregnancy. As red blood cell (RBC) volume increases approximately 18 to 30 percent, the hematocrit normally decreases during gestation but not below 30 percent.

Pregnancy is hypercoagulable state, with increases in the levels of the majority of the procoagulant factors and a decrease in the fibrinolytic system and in some of the natural inhibitors of coagulation. Blood urea nitrogen (BUN) and creatinine normally decrease during pregnancy as a result of the increased glomerular filtration rate (GFR). Despite alterations in thyroid morphology, histology, and laboratory indices, the normal pregnant woman is euthyroid, with the levels of free T4 within non-pregnant norms. Pregnancy is associated with a peripheral resistance to insulin, primarily mediated by human placental lactogen. Insulin resistance increases as pregnancy advances and results in hyperglycemia, hyperinsulinemia, and hyperlipidemia in response to feeding, especially in the third trimester. Two consistent and significant ocular changes occur during pregnancy are: increased thickness of the cornea and decreased intraocular pressure. Pregnancy either does not change or minimally decreases visual fields; therefore, any complaints of visual field changes are atypical and need further evaluation.

Suggested Reading:

  1. Gordon M. Maternal physiology. In Obstetrics: Normal and Problem Pregnancies; 5th edition. Eds: Gabbe SG, Niebyl JR, Simpson JL. Publisher: Churchill Livingstone Elsevier; 2007
  2. Bernstein I, Ziegler W, Badger G. Plasma volume expansion in early pregnancy. Obstet Gynecol 2001;97:669-772
  3. El-Hennawy A, Bassi T, Koradia N, et al. Transient gestational diabetes insipidus: report of two cases and review of pathophysiology and treatment. J Maten Fetal Med 2003;14:249-354
  4. Harirah H, Donia S, Nasrallah F. Effect of gestational age and position on peak expiratory flow rate: A Longitudinal study. Obstet Gynecol 2005;105:372-385
  5. Dinn R, Harris A, Marcus P. Ocular changes in pregnancy. Obstet Gynecol Surv 2003;58:137-141
  6. Lain KY, Markovic N, Ness RB, et al. Effect of smoking on uric acid and other metabolic markers throughout normal pregnancy. J Clin Endocrinol Metab 2005;90:5743-5750
  7. Murphy MM, Scott JM, McPartlin JM et al. The pregnancy-related decrease in fasting plasma homocysteine is not explained by folic acid supplementation, hemodilution, or a decrease in albumin in a longitudinal study. Am J Clin Nutr 2002;76:614-617
  8. Mandel SJ, Spencer CA. Hollowell JG. Are detection and treatment of thyroid insufficiency in pregnancy feasible? Thyroid 2005;15:44-49
  9. Walker JA, Illions EH, Huddleston JF et al. Racial comparisons of thyroid function and autoimmunity during pregnancy and the postpartum period. Obstet Gynecol 2005;106:1365-1370
  10. Paton L, Alexander J, Nowson C et al. Pregnancy and lactation have no long-term deleterious effect on measures of bone mineral in healthy women: a twin study. Am J Clin Nutr 2003;77:707-711
  11. Ross MG, Ervin G, Novak D. Fetal Physiology. In Obstetrics: Normal and Problem Pregnancies; 5th edition, Eds: Gabbe SG, Niebyl JR, Simpson JL. Publisher: Churchill Livingstone Elsevier; 2007
  12. American College of Obstetricians and Gynecologists: Compendium of selected publications; Volume II: Practice Bulletins. Washington DC. ACOG - 2008

Published: 6 August 2009

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