9.1 Antepartum Care & High-Risk Pregnancy Complications

Antepartum Care & High-Risk Pregnancy Complications

Antepartum care provides systematic surveillance of the pregnant woman and developing fetus to optimize perinatal outcomes. Professional nursing practice demands mastery of maternal anatomical and physiological adaptations, clinical risk assessment tools, standardized prenatal screening schedules, and evidence-based management of acute antepartum emergencies.

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Maternal Physiological Adaptations to Pregnancy

During pregnancy, virtually every maternal organ system undergoes profound anatomical and physiological remodeling to support fetal growth and prepare the body for labor and lactation.

Cardiovascular System Adaptations

• Intravascular Blood Volume: Total maternal blood volume expands by 40% to 50% (approximately 1,200 to 1,500 mL) above non-pregnant baseline, peaking between 28 and 34 weeks of gestation. Plasma volume increases by approximately 50%, whereas red blood cell (RBC) mass expands by only 20% to 30% through erythropoietin stimulation. This differential creates physiologic anemia of pregnancy (hemodilution). Common trimester-specific anemia cutoffs used in obstetric care are:
  • First Trimester: Hemoglobin < 11.0 g/dL (Hematocrit < 33%)
  • Second Trimester: Hemoglobin < 10.5 g/dL (Hematocrit < 32%)
  • Third Trimester: Hemoglobin < 11.0 g/dL (Hematocrit < 33%)
• Cardiac Output (CO): Increases by 30% to 50%, mediated by an increase in stroke volume (early pregnancy) and maternal heart rate (increasing by 10 to 15 beats per minute by the third trimester). Auscultation frequently reveals a benign, soft systolic ejection murmur (Grade I or II) over the left sternal border due to increased blood flow velocity across normal heart valves.
• Systemic Vascular Resistance (SVR): Progesterone, prostacyclin, and relaxin induce systemic smooth muscle relaxation and peripheral vasodilation. Consequently, systemic blood pressure decreases slightly during the second trimester (diastolic dropping 5 to 10 mmHg) before returning to pre-pregnancy baseline levels at term. A blood pressure of 140/90 mmHg is never normal in pregnancy.
• Supine Hypotensive Syndrome (Aortocaval Compression): When a pregnant patient beyond 20 weeks lies flat in the supine position, the heavy gravid uterus compresses the inferior vena cava (IVC) and descending aorta against the vertebral column. This causes a precipitous drop in venous return, stroke volume, and arterial blood pressure, manifesting as maternal lightheadedness, pallor, diaphoresis, nausea, and acute fetal bradycardia. The immediate nursing intervention is placing the patient in a left lateral tilt position (placing a wedge under the right hip) to displace the uterus off the IVC.

Respiratory, Renal, and Gastrointestinal Adaptations

• Respiratory: The growing uterus elevates the diaphragm by up to 4 cm. Progesterone acts as a direct central respiratory stimulant, increasing tidal volume by 30% to 50% while respiratory rate remains unchanged. This produces physiological hyperventilation, resulting in a compensated respiratory alkalosis (arterial blood gas: pH 7.40–7.45, PaCO2 27–32 mmHg, serum HCO3 18–22 mEq/L). This low maternal PaCO2 facilitates fetal-to-maternal carbon dioxide diffusion across the placenta.
• Renal: Renal blood flow and glomerular filtration rate (GFR) increase by 50% starting in the first trimester. As a result, normal serum levels of blood urea nitrogen (BUN) and creatinine decrease substantially during pregnancy. Normal pregnancy serum creatinine is 0.4 to 0.8 mg/dL; a serum creatinine >=0.9 mg/dL suggests underlying renal impairment or preeclampsia.
• Gastrointestinal: Progesterone decreases smooth muscle tone, slowing gastric emptying and intestinal motility, which promotes constipation and hemorrhoids. Relaxation of the lower esophageal sphincter produces pyrosis (heartburn). Delayed gallbladder emptying increases the risk of gallstone formation (cholelithiasis).

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Obstetric Estimation: Nägele's Rule & GTPAL Classification

Accurate calculation of gestational age and detailed obstetric parity documentation are foundational nursing responsibilities.

Calculating Estimated Date of Delivery (Nägele's Rule)

Nägele's rule assumes a regular 28-day menstrual cycle with ovulation occurring on day 14. To calculate the Estimated Date of Delivery (EDD):

$\text{EDD} = \text{First Day of Last Menstrual Period (LMP)} + 7 \text{ Days} - 3 \text{ Months} + 1 \text{ Year}$

Worked Clinical Example:

• Patient reports the first day of her LMP was May 12, 2026.
• Step 1: Add 7 days to May 12 -> May 19, 2026.
• Step 2: Subtract 3 months from May -> February 19, 2026.
• Step 3: Add 1 year -> February 19, 2027.

The Five-Digit GTPAL Obstetric Classification

The GTPAL system provides an exact obstetric summary of a patient's reproductive history:

• G (Gravida): Total number of pregnancies, regardless of duration or outcome, including the current ongoing pregnancy.
• T (Term Births): Number of pregnancies delivered at 37 weeks 0 days or beyond (both live births and stillbirths). Multiple gestations (twins/triplets) delivered together count as 1 pregnancy event.
• P (Preterm Births): Number of pregnancies delivered between 20 weeks 0 days and 36 weeks 6 days (live births and stillbirths). Multiple gestations count as 1 pregnancy event.
• A (Abortions): Number of pregnancies ending prior to 20 weeks 0 days (includes spontaneous miscarriages and elective or therapeutic pregnancy terminations).
• L (Living Children): Total number of currently living children. In this category, twin and higher-order multiple infants are counted individually.

Practice Vignette: A client is currently 14 weeks pregnant. Her obstetric history reveals she gave birth to full-term twin boys at 38 weeks who are now 4 years old. She delivered a daughter at 33 weeks who is now 2 years old. She had an elective termination at 8 weeks gestation three years ago, and a spontaneous miscarriage at 11 weeks gestation last year. What is her GTPAL?

• G: 5 (current pregnancy + twins pregnancy + preterm daughter pregnancy + elective abortion + miscarriage)
• T: 1 (one pregnancy delivered at 38 weeks)
• P: 1 (one pregnancy delivered at 33 weeks)
• A: 2 (one elective termination at 8 weeks + one miscarriage at 11 weeks)
• L: 3 (two twin sons + one daughter)
• Documented Classification: G5-T1-P1-A2-L3

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Core Prenatal Screening & Immunoprophylaxis

Standardized antenatal screenings identify maternal-fetal risks requiring timely prophylactic intervention.

Group B Streptococcus (GBS) Screening & Intrapartum Prophylaxis

Streptococcus agalactiae (Group B Strep) is a common commensal organism of the gastrointestinal and lower genital tracts. While asymptomatic in healthy adults, vertical transmission during vaginal delivery can cause devastating neonatal early-onset sepsis, pneumonia, and meningitis.

• Screening Protocol: Universal screening is conducted between 35 weeks 0 days and 37 weeks 6 days of gestation via a combined lower vaginal and rectal swab.
• Indications for Intrapartum Antibiotic Prophylaxis (IAP):
  1. Documented positive GBS vaginal-rectal culture during current pregnancy.
  2. History of a previous infant diagnosed with invasive GBS disease.
  3. Documented GBS bacteriuria at any time during the current pregnancy (indicates heavy maternal colonization; does not require repeat third-trimester culture).
  4. Unknown GBS culture status at the onset of labor with any of the following risk factors:
     • Preterm labor (<37 weeks gestation)
     • Rupture of membranes (ROM) >=18 hours
     • Maternal intrapartum temperature >=38.0°C (100.4°F)
• Antibiotic Regimen: The gold standard is Intravenous Penicillin G: 5 million units IV loading dose, followed by 2.5 to 3.0 million units IV every 4 hours until neonatal delivery. (Intravenous Ampicillin 2g loading dose then 1g q4h is an acceptable alternative). For penicillin-allergic patients with low anaphylaxis risk, IV Cefazolin is used; for high-risk penicillin anaphylaxis, IV Clindamycin (if isolate confirmed susceptible) or IV Vancomycin (20 mg/kg q8h, maximum 2 g per dose) is indicated. Adequate prophylaxis requires at least 4 hours of intravenous antibiotic therapy prior to delivery.

Gestational Diabetes Mellitus (GDM) Screening

Placental production of human placental lactogen (hPL), cortisol, and progesterone creates maternal peripheral insulin resistance during the second half of pregnancy, ensuring adequate glucose shunting to the fetus.

• 1-Hour Oral Glucose Challenge Test (GCT): Administered between 24 and 28 weeks of gestation. The patient ingests a 50-gram oral glucose load without regard to the time of last meal. Venous plasma glucose is measured at 1 hour. A threshold of >=130 to 140 mg/dL (7.2 to 7.8 mmol/L) is considered positive and mandates diagnostic 3-hour testing.
• 3-Hour 100g Diagnostic Oral Glucose Tolerance Test (OGTT): Performed in the morning following an overnight fast of 8 to 14 hours. Plasma glucose is drawn fasting, and at 1, 2, and 3 hours following ingestion of 100 grams of glucose.
  • Fasting: >=95 mg/dL (5.3 mmol/L)
  • 1-Hour: >=180 mg/dL (10.0 mmol/L)
  • 2-Hour: >=155 mg/dL (8.6 mmol/L)
  • 3-Hour: >=140 mg/dL (7.8 mmol/L)
  • Diagnostic Criterion: Gestational diabetes is confirmed when two or more threshold values are met or exceeded.

Rh Alloimmunization & Rho(D) Immune Globulin (RhoGAM)

Rh incompatibility occurs when an Rh-negative mother carries an Rh-positive fetus. If fetal erythrocytes enter maternal circulation (fetomaternal hemorrhage), the maternal immune system recognizes the foreign Rh(D) antigen and produces anti-D antibodies (sensitization). In subsequent Rh-positive pregnancies, maternal IgG antibodies cross the placenta, lysing fetal erythrocytes and causing erythroblastosis fetalis (severe hemolytic anemia, hydrops fetalis, and fetal death).

• Laboratory Surveillance: Indirect Coombs test performed on maternal blood at initial visit and at 28 weeks detects circulating anti-Rh antibodies. If the indirect Coombs test is negative (mother is unsensitized), immunoprophylaxis is indicated.
• Rho(D) Immune Globulin (RhoGAM 300 mcg IM) Administration Windows:
  1. Routinely administered at 28 weeks of gestation to all unsensitized Rh-negative women.
  2. Administered within 72 hours postpartum for an unsensitized Rh-negative mother after delivery of an Rh-positive infant. Eligibility depends on maternal anti-D sensitization, not a requirement for a negative infant direct Coombs test.
  3. Administered after any potential fetomaternal hemorrhage event (spontaneous or induced abortion, ectopic pregnancy, chorionic villus sampling, amniocentesis, external cephalic version, or blunt abdominal trauma).
• Kleihauer-Betke (KB) Test: An acid elution blood test that quantifies the exact volume of fetal blood in maternal circulation to calculate whether additional vials of RhoGAM are required beyond the standard 300 mcg dose (which covers up to 30 mL of fetal whole blood).

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Hypertensive Disorders of Pregnancy & Magnesium Sulfate

Hypertensive disorders complicate up to 10% of pregnancies and represent a leading cause of maternal and perinatal morbidity.

Clinical Spectrum & Diagnostic Criteria

• Gestational Hypertension: New-onset systolic BP >=140 mmHg or diastolic BP >=90 mmHg on two occasions at least 4 hours apart after 20 weeks of gestation, in the absence of proteinuria or systemic features of preeclampsia.
• Preeclampsia: New-onset hypertension after 20 weeks with proteinuria (>=300 mg/24 hours or protein-to-creatinine ratio >=0.3 mg/mg). If quantitative testing is unavailable, use dipstick >=2+. New end-organ features can establish preeclampsia without proteinuria.
• Preeclampsia with Severe Features: Manifests when hypertension is severe (SBP >=160 mmHg or DBP >=110 mmHg, confirmed promptly within about 15 minutes; persistent severe hypertension requires urgent treatment, ideally as soon as possible within 30–60 minutes, without waiting 4 hours) OR in the presence of any of the following systemic end-organ dysfunctions (even without proteinuria):
  • Progressive renal insufficiency (serum creatinine >1.1 mg/dL or doubling of baseline)
  • Hepatic involvement (epigastric or right upper quadrant abdominal pain unresponsive to medication, AST/ALT elevated to twice the upper limit of normal)
  • Thrombocytopenia (platelet count < 100,000/mcL)
  • Pulmonary edema
  • New-onset cerebral or visual disturbances (photophobia, scotomata, severe persistent headache)
• HELLP Syndrome: A severe subtype characterized by Hemolysis (microangiopathic hemolytic anemia with schistocytes on peripheral smear, elevated total bilirubin >=1.2 mg/dL, elevated LDH >600 U/L), Elevated Liver enzymes (AST/ALT >=2x normal), and Low Platelets (<100,000/mcL).
• Eclampsia: The onset of new generalized tonic-clonic seizures in a patient with preeclampsia that cannot be attributed to other neurological causes.

Magnesium Sulfate Protocol & Toxicity Surveillance

Magnesium sulfate is the pharmacological gold standard for seizure prophylaxis and neuroprotection in preeclampsia with severe features and eclampsia. It acts by blocking neuromuscular transmission and depressing central nervous system irritability. It is not an antihypertensive agent.

• Dosage Protocol:
  • Loading Dose: 4 to 6 grams IV diluted in 100 mL IV fluid, infused piggyback over 20 to 30 minutes.
  • Maintenance Infusion: 1 to 2 grams/hour IV continuous infusion via a dedicated volumetric infusion pump.
• Mandatory Nursing Assessment Parameters (Hourly Surveillance):
  1. Deep Tendon Reflexes (DTRs): Patellar reflexes must be evaluated hourly. Normal is 2+. Hyporeflexia or loss of DTRs is the earliest clinical sign of hypermagnesemia.
  2. Respiratory Rate: Must be >=12 breaths per minute. Bradypnea (<12) indicates impending respiratory arrest.
  3. Hourly Urine Output: Must remain >=30 mL/hour (or >=0.5 mL/kg/hr) monitored via an indwelling Foley catheter with urometer. Magnesium is excreted exclusively by the kidneys; oliguria leads to rapid toxic accumulation.
  4. Continuous Fetal Heart Rate: Decreased baseline variability is expected on magnesium therapy.
• Serum Magnesium Thresholds:
  • Therapeutic Range: 4.0 to 7.0 mEq/L (4.8 to 8.4 mg/dL)
  • Loss of Patellar Reflexes: 8.0 to 10.0 mEq/L
  • Respiratory Depression: 10.0 to 12.0 mEq/L
  • Cardiac Conduction Defects / Arrest: >15.0 mEq/L
• Emergency Antidote: If magnesium toxicity occurs (absent DTRs, bradypnea, lethargy, oliguria), immediately stop the magnesium sulfate infusion and administer Calcium Gluconate 10% solution: 1 gram (10 mL) IV push slowly over 3 to 5 minutes at the bedside.

Nursing Management of Eclamptic Seizures

During an eclamptic seizure, the nurse's immediate priority is maternal safety and airway protection:

1. Call for urgent obstetric code assistance.
2. Turn the patient onto her left lateral side to prevent aspiration and displace the uterus.
3. Protect the airway; do not insert anything into the patient's mouth or attempt to restrain limbs.
4. Following seizure cessation, suction oral secretions and apply 100% oxygen at 8 to 10 L/min via non-rebreather mask.
5. Administer an IV bolus of magnesium sulfate (2 grams IV over 5 to 10 minutes if already receiving maintenance infusion).
6. Monitor maternal vital signs and continuous fetal heart rate (transient fetal bradycardia and late decelerations are common during and immediately following a seizure).
7. Stabilize the mother hemodynamically and prepare for delivery; delivery of the fetus and placenta is the definitive cure for preeclampsia/eclampsia once the mother is stable.

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Third-Trimester Bleeding: Placenta Previa vs. Abruptio Placentae

Third-trimester vaginal bleeding is an obstetric emergency requiring rapid clinical differentiation between placenta previa and abruptio placentae.

Placenta Previa

Placenta previa occurs when the placenta implants abnormally in the lower uterine segment, completely or partially covering the internal cervical os.

• Pathophysiology & Presentation: As the lower uterine segment thins and effaces in late pregnancy, placental anchoring villi tear from the uterine wall. The classic presentation is sudden, painless, bright red vaginal bleeding occurring in the second or third trimester. The abdomen remains soft, relaxed, and non-tender with normal uterine resting tone.
• CRITICAL NURSING PROHIBITION: NEVER perform a digital vaginal examination on a patient with third-trimester vaginal bleeding until ultrasound has localized the placenta. Inserting a finger into the cervix can puncture the placenta, provoking catastrophic, fatal exsanguination.
• Management: Confirm placental location by transabdominal or transvaginal ultrasound. Individualize observation or admission according to bleeding, gestation and access to emergency care; routine bed rest has no proven benefit. Establish IV access and arrange blood testing/crossmatch. Give antenatal corticosteroids when preterm birth is anticipated within the applicable gestational window. Persistent complete placenta previa requires planned cesarean delivery, or urgent delivery for uncontrolled hemorrhage or fetal compromise.

Abruptio Placentae (Placental Abruption)

Abruptio placentae is the premature detachment of a normally implanted placenta from the uterine wall prior to delivery.

• Pathophysiology & Presentation: Rupture of maternal decidual spiral arteries leads to retroplacental hematoma formation. The hallmark presentation is sudden, severe, unremitting abdominal or lower back pain accompanied by dark red vaginal bleeding (external abruption). In 20% of cases, bleeding is entirely concealed behind the placenta, producing no visible vaginal blood.
• Physical Examination Findings: The uterus is board-like, rigid, and exquisitely tender with continuous hypertonic contractions (tachysystole). Maternal hypovolemic shock out of proportion to visible external bleeding may develop rapidly. Fetal monitoring demonstrates severe fetal distress (recurrent late decelerations, loss of variability, or persistent bradycardia).
• Risk Factors: Maternal chronic hypertension, preeclampsia, cocaine use, cigarette smoking, blunt abdominal trauma (e.g., motor vehicle crash), multiparity, and rapid uterine decompression (e.g., rupture of membranes with polyhydramnios).
• Severe Complications: Massive retroplacental clot formation consumes maternal clotting factors and triggers systemic release of tissue thromboplastin, placing the patient at extreme risk for Disseminated Intravascular Coagulation (DIC). Nursing care requires large-bore IV access, hemorrhage resuscitation, continuous fetal monitoring, and urgent obstetric review. Activate massive transfusion for major bleeding; expedite birth for maternal or fetal compromise. Cesarean birth is usually required for a compromised live fetus unless vaginal birth is imminent; after fetal death, vaginal birth is preferred when maternal condition permits.

Comparison: Placenta Previa versus Abruptio Placentae