pregnancy (gestation)

Introduction

Childbirth generally occurs ~ 38 weeks after conception or ~ 40 weeks from the last normal menstrual period.

Physiology

Cardiology

• hemodynamic changes:
  • increased plasma volume (1100-1500 mL)
  • increased red cell mass (300 mL)
  • increased cardiac output
  • heart rate increase 20-30% (< 100/min)
  • blood pressure
    • decreases soon after conception
    • reaches a nadir in 20 weeks
  • hypertension affects 10% of pregnant women
    • blood pressure (BP) > 140/90
    • increase of systolic BP of > 30 mm Hg
    • increase of diastolic BP of > 15 mm Hg
• auscultation
  • systolic ejection murmur in pulmonic area, not more than III/VI is a normal finding during pregnancy
  • 3rd heart sound (S3) is common in pregnancy; S4 heart sound is pathologic
  • grade 1-2/6 systolic murmur normal
  • grade 3/6 systolic murmur or any diastolic murmur is pathologic
  • diastolic rumble should raise suspicion of mitral stenosis
• absolute contraindications to pregnancy
  • Marfan syndrome with dilated aortic root
    • increased risk of dissection & rupture due to hormonal- induced softening of connective tissue
    • unpredictable risk of dissection & rupture, regardless of aortic size
  • Eisenmenger's syndrome (50% maternal mortality)
  • primary pulmonary hypertension
  • symptomatic aortic stenosis
  • symptomatic mitral stenosis
  • symptomatic dilated cardiomyopathy
• heart failure
  • mild dyspnea on exertion is normal
  • orthopnea, paroxysmal noctural dyspnea pathologic
  • minimize activity to decrease cardiac output
  • reduce sodium in diet
  • minimize anemia: vitamin & iron supplements
  • avoid ACE inhibitors, ARBs, aldosterone antagonists
• arrhythmias
  • atrial premature contractions normal
  • ventricular premature contractions normal
  • atrial fibrillation, atrial flutter, ventricular tachycardia are pathologic
  • cardioversion may be performed if necessary
    • simultaneous monitoring of fetal heart
• surgery
  • during 1st trimester associated with increased fetal loss
  • percutaneous balloon valvuloplasty well tolerated
    • aortic, mitral & pulmonary valvuloplasty
    • lead shielding of fetus
• pharmaceutical agents
  • contraindicated
    • captopril, phenytoin, warfarin, tetracycline
  • drugs which cross placenta, but may be used safely
    • digoxin, quinidine, procainamide, verapamil
    • beta blockers
      • monitor fetal growth
      • may be associated with fetal growth retardation, neonatal bradycardia & hypoglycemia
• delivery
  • average blood loss
    • 500-800 mL with vaginal delivery
    • 800 mL with cesarean section
  • with each uterine contraction, 500 mL of blood is released into the circulation
  • no need for antibiotic prophylaxis for uncomplicated vaginal delivery
• prosthetic valves
  • most women of child-bearing age who need valve replacement receive bioprosthetic valves
  • generally, they do not receive anticoagulation
  • in pregnant women with mechanical valves, switch from warfarin to subcutaneous heparin
  • heparin is associated with increased fetal loss

* pulmonary edema is pathologic

Nephrology: (Renal)

• renal enlargement (1 cm)
• dilatation of the renal calyces, pelvis & ureters
  • features can resemble obstructive uropathy
  • increases risk for ascending pyelonephritis
• 30-50% increase in glomerular filtration rate (GFR) & renal blood flow
• decrease in serum creatinine
  • mean serum creatinine of 0.5 mg/dL, 0.8 mg/dL (max)
• mean urea nitrogen of 18 mg/dL, 26 mg/dL (max)
• intermittent glycosuria (< 1 g/day) independent of plasma glucose
• proteinuria
  • normal < 300 mg/day, may be postural
  • women with underlying renal insufficiency may have a significant increase in proteinuria during pregnancy associated with poorer fetal prognosis, not associated with any worsening of their renal disease
  • women with diabetes mellitus type-1 with microalbuminuria but normal renal function & blood pressure have pregnancy outcomes similar to the general population
• increased uric acid secretion
• increased ureteral peristalsis
• 50% increase in plasma volume
• increased total body water (6-8 L) with osmostat resetting
  • mildly diminished plasma osmolality
• changes in sodium metabolism (not uncommon)
  • mild hyponatremia due to changes in ADH response to osmolality
  • renal sodium retention
• decrease in blood pressure
• hypertension, proteinuria, or elevated serum creatinine during the first antepartum visit suggests chronic glomerulonephritis

Endocrine

• increased plasma levels of
  • renin
  • angiotensin II
  • aldosterone
  • cortisol
  • estrogens
  • prostaglandins E2 & I2
  • progesterone
• insensitivity to pressor effects of:
  • angiotensin II
  • norepinephrine
• progesterone counteracts K+ excreting effects of aldosterone
• 30-50% increase in requirement for thyroxine
  • similar increase in requirement for iodine
  • subclinical hypothyroidism may adversely affect outcome

Immunology

• 3rd trimester is associated with immunosuppression
• defects in neutrophil chemotaxis
• defect in T-cell mediated cellular immunity
• risk of disseminated Herpes zoster
• risk of disseminated coccidioidomycosis

Hematology

• anemia
  • decrease in hemoglobin as low at 10 mg/dL
  • increase in plasma volume (1100-1500 mL)
  • lesser increase red cell mass (300 mL)
  • reduced viscosity of blood
  • iron deficiency generally involved
    • iron preferentially routed to fetus
    • 1000 mg of iron generally required per pregnancy
      • blood loss
      • fetal requirements
• aplastic anemia may be associated with pregnancy
  • resolves with termination of pregnancy
  • may recur with subsequent pregnancy
• sickle cell disease
  • increased maternal mortality
  • increased fetal morbidity
  • prophylactic transfusion is NOT of benefit
• thrombocytopenia
  • mild gestational thrombocytopenia (> 75,000/uL) in 8.3%
    • generally develops in 3rd trimester
    • no specific treatment needed
  • chronic immune thrombocytopenic purpura (ITP)
    • may be worsened by pregnancy
    • IgG of ITP crosses placenta
    • prednisone is 1st line
    • IV immune globulin if refractory to prednisone
  • HELLP syndrome
• hemorrhagic disorders
  • factor VIII autoantibodies
  • factor VIII-vWF complex increases in 2nd trimester with a rapid decrease post-partum
• thrombotic disorders
  • pregnancy should be considered a hypercoagulable state
    • concentration of procoagulant factors increase progressively during pregnancy
    • protein S & fibrinolytic activity decrease
      • C4b binding protein increases during pregnancy decreasing the amount of free (& functional) protein S
    • coagulation cascade may be activated in the placenta
    • increased venous stasis in lower extremities
    • labor & delivery, especially C-section increase risk of thrombosis
  • normal levels of plasma fibrinogen in the 3rd trimester of pregnancy is about twice the non-pregnant state
  • disseminated intravascular coagulation (DIC)
    • most common thrombotic disorder in pregnancy
    • abruptio placenta is the most common cause of DIC
    • amniotic fluid embolism
    • intrauterine fetal death
    • saline-induced abortion
    • septic abortion
    • frequent association with fatty liver of pregnancy
  • placental tissue factor or activated clotting factors entering the mother's circulation may trigger DIC

Dermatology

• hyperpigmentation
• striae gravidarum
• hair & nails
  • hair may thicken during pregnancy with telogen effluvium occurring 3 months post partum
  • nails may grow faster during pregnancy
• vascular changes
  • spider angiomas
  • hemorrhoids & varicose veins
  • palmar erythema
  • peripheral edema in 35-85%*
  • vaginal erythema (Chadwick sign)
  • blue discoloration of the cervix (Goodell sign)
  • gingival hyperemia & edema

General

• higher risk for stillbirth > 40 years of age
• risk of genetic abnormalities accelerates after 35 years of age
• nausea/vomiting of pregnancy reduces risk of spontaneous abortion

Contraindications

• hypertrophic cardiomyopathy
  • ventricular outflow tract obstruction
• LV systolic dysfunction with LV ejection fraction < 40% & class 3 or 4 heart failure
• severe pulmonary hypertension

Laboratory

• urinalysis for asymptomatic bacteriuria (all women)
  • increased risk for pyelonephritis; treatment indicated
• complete blood count for iron deficiency anemia
  • workup anemia
• hepatitis B serology
• syphilis serology
• blood type & screen
• serum TSH
• serum progesterone predicts viability in early pregnancy
• serum 25-OH vitamin D in women with immediated family member with multiple sclerosis
• urine drug screen on 1st visit (all pregnant women)
• serum sodium: mild hyponatremia from a reset in ADH response to low osmolality is normal & does not require treatment

Complications

• see pregnancy disorder
• short interpregnancy interval is not associated with adverse outcomes
• weight gain between pregnancies increases risk for adverse birth outcomes (stillbirth, neonatal mortality)
• increased risk for pyelonephritis
• loss of husband (father of child) during pregnancy associated with shortened adult life span in offspring
• women > 40 years of age at higher risk than women 20-34 years for adverse events (chromosomal aberrations, miscarriage, & preterm birth) 11% vs 5%
• women with chronic renal failure at increased risk for pre-eclampsia, progression of chronic renal failure, ESRD, preterm delivery, gestational hypertension, intrauterine growth retardation & spontaneous abortion

• disease interaction(s) of congenital heart disease with pregnancy
• disease interaction(s) of obesity/overweight with pregnancy
• interaction(s) of breast cancer with pregnancy

Management

• preconception risk assessment (see conception)
• folic acid 0.4-0.8 mg QD*
  • begin at least 1 month prior to conception & continue for 2-3 months after delivery
• calcium supplementation for prevention of pre-eclampsia in populations where calcium intake is low [NGC, WHO]
• increase levothyroxine dose in women with hypothyroidism 30-50% prior to conception or when pregnancy discovered if unplanned
• vitamin D supplementation
  • little effect on maternal or neonatal outcomes
  • vitamin D (1000 IU QD) beginning at 14-17 weeks gestation may increase bone mineral content among infants born in winter months
  • maternal serum 25-hydroxy vitamin D declines from 14-34 weeks gestation in women who deliver in winter & spring unless supplemented with vitamin D
  • maternal vitamin D deficiency duing pregnancy associated with increased risk of multiple sclerosis in offspring
  • 1000-2000 IU vitamin D daily for women with immediate family member with multiple sclerosis & serum 25-OH vitamin D < 20 ng/mL
• vaccinations
  • Tdap after 20 weeks gestation (all pregnancies); 27-36 weeks of gestation
    • dT q 4 weeks x 2 after Tdap if not previously vaccinated for tetanus
  • influenza vaccine can be given any trimester
  • influenza vaccination between 20 & 36 weeks' gestation reduces influenza in mothers & their infants (2-4% both)
    • does not reduce influenza in infants of HIV+ mothers
  • measles/mumps/rubella vaccine (MMR) & varicella vaccine
    • immediately postpartum in nonimmune women or
      • >= 4 weeks prior to conception (live virus vaccine)
• dietary interventions during pregnancy limit maternal weight gain & reduce risk for some maternal complications
  • a healthy diet may reduce risk of pre-term delivery
• weight gain targets:
  • pre-pregnancy BMI < 18.5 (underweight): 28-40 pounds
  • pre-pregnancy BMI 18.4-24.9 (normal): 25-35 pounds
  • pre-pregnancy BMI 25.0-29.9 (overweight): 15-25 pounds
  • pre-pregnancy BMI > 30 (obese): 11-20 pounds
• ACOG recommends daily physical activity/exercise during pregnancy & the postpartum period
• diet & exercise during pregnancy may affect incidence of macrosomia (> 4000 g)
  • exercise during pregnancy reduces risk of macrosomia & does not increase risk for small babies (<2500 g)
• physical activity during pregnancy either decreases duration of labor or has no effect on it
• pregnant & breast-feeding women should eat of a variety of fish two to three times a week (8-12 oz weekly) to support growth & development
  • the fish should be low in methylmercury
• prenatal & postpartum home care may reduce maternal & child mortality
• topical agents are often preferred during pregnancy because of lower risks for systemic effects
  • exception is topical tazarotene pregnancy category X
• antipsychotic use during pregnancy
  • risk of extrapyramidal signs in infants born to mothers taking antipsychotics in the 3rd trimester of pregnancy
  • associated with minimal risk during pregnancy
• general surgery as safe for pregnant women as it is for nonpregnant women

* folic acid fortification of cereal grains prevents > 1300 neural tube defects annually

* folic acid supplementation in high-risk pregnancy is only 37%

Notes

• a pregnant woman capable of decision making should be allowed to decline recommended medical or surgical interventions
  • directed counseling is recommended, but do not try to coerce women into making a specific decision
  • attempt to understand context of the decision & acknowledge prognostic uncertainty
  • consider ethics consult experts if it may help resolve the conflict
• no action should be taken against clinicians who decline to perform court-ordered interventions

More general terms

• reproduction

More specific terms

• high-risk pregnancy
• intrauterine pregnancy
• multigravida
• multiple gestation (multiple pregnancy)
• post-term pregnancy; prolonged pregnancy
• primigravida
• teen birth; teenage pregnancy
• term pregnancy
• unintended pregnancy

Additional terms

• abortion
• alcohol during pregnancy
• conception
• fetus
• labor & delivery
• medications contraindicated during pregnancy
• medications during pregnancy
• miscarriage
• pregnancy category
• pregnancy disorder; obstetric disorder; pregnancy complication
• pregnancy test
• prenatal care

Patient information

pregnancy patient information