Complications of Pregnancy

Learning Objectives

By the end of this page, you should be able to:

• Classify the hypertensive disorders of pregnancy and distinguish preeclampsia from chronic and gestational hypertension.
• Describe the pathophysiology, diagnostic criteria, and management of preeclampsia and eclampsia.
• Explain how gestational diabetes mellitus (GDM) is screened, diagnosed, and managed, and list its fetal and maternal risks.
• Recognize the clinical presentation of ectopic pregnancy and differentiate it from other causes of first-trimester bleeding and pain.
• Compare placenta previa, placental abruption, and vasa previa on presentation and management.
• Identify red-flag symptoms in pregnancy that require emergency evaluation.

Quick Answer

Pregnancy complications are conditions that threaten maternal or fetal wellbeing and fall into a few high-yield groups: hypertensive disorders (gestational hypertension, preeclampsia, eclampsia, HELLP syndrome), metabolic disease (gestational diabetes), abnormal implantation (ectopic pregnancy), and placental problems (placenta previa, placental abruption, vasa previa). Each has a distinct mechanism — vascular endothelial dysfunction, insulin resistance, tubal implantation, or abnormal placental positioning — but they share a common exam logic: recognize the presentation, know the diagnostic threshold, and match it to the correct next step, which is often delivery, monitoring, or emergency surgery. These conditions matter because they remain leading causes of maternal and perinatal morbidity and mortality worldwide, and early recognition changes outcomes dramatically.

Hypertensive Disorders of Pregnancy

Overview

Not all high blood pressure in pregnancy is the same disease, and the distinction matters clinically and on exams. The four categories are: chronic hypertension (present before 20 weeks or persisting after 12 weeks postpartum), gestational hypertension (new-onset after 20 weeks, no proteinuria or organ dysfunction), preeclampsia (new-onset hypertension plus proteinuria or evidence of end-organ damage), and eclampsia (preeclampsia plus seizures). Superimposed preeclampsia occurs when a woman with chronic hypertension develops new proteinuria or organ dysfunction.

Preeclampsia

Definition. Preeclampsia is new-onset hypertension (systolic ≥140 mmHg or diastolic ≥90 mmHg on two occasions, at least 4 hours apart, after 20 weeks gestation) accompanied by proteinuria (≥300 mg/24 hr, protein:creatinine ratio ≥0.3, or dipstick ≥2+) or, in the absence of proteinuria, evidence of new organ dysfunction — thrombocytopenia, renal insufficiency, impaired liver function, pulmonary edema, or new cerebral/visual disturbances.

Explanation. The underlying problem is abnormal placentation: cytotrophoblasts fail to properly invade and remodel the maternal spiral arteries, leaving them narrow and high-resistance. This causes placental hypoperfusion, which triggers release of anti-angiogenic factors (notably soluble fms-like tyrosine kinase-1, sFlt-1) into the maternal circulation. These factors cause widespread maternal endothelial dysfunction — the reason preeclampsia is a multi-organ disease rather than "just" high blood pressure. Endothelial injury explains the proteinuria (glomerular damage), headaches and visual changes (cerebral vasospasm/edema), epigastric pain (hepatic capsule swelling), and edema (increased vascular permeability).

Example. A woman at 32 weeks with no prior hypertension presents with a blood pressure of 150/100 mmHg on two readings 6 hours apart and 2+ protein on urine dipstick. This meets criteria for preeclampsia.

Real-world example. A first-time mother (nulliparity is a major risk factor) develops a severe frontal headache and blurred vision at 36 weeks. Her blood pressure is 165/110 mmHg and labs show platelets of 90,000/µL. This is severe preeclampsia — she needs immediate stabilization, magnesium sulfate for seizure prophylaxis, antihypertensives, and delivery is the definitive treatment.

Why it matters. Preeclampsia is a leading cause of maternal death and a major cause of iatrogenic preterm birth, because delivery — even when the fetus is preterm — is the only cure.

Common misunderstanding. Students often think preeclampsia is diagnosed by blood pressure alone. In fact, the diagnosis requires either proteinuria or another marker of end-organ dysfunction; isolated hypertension after 20 weeks without either is gestational hypertension, a different (though related and sometimes progressive) category.

Eclampsia and HELLP Syndrome

Eclampsia is the occurrence of new-onset generalized tonic-clonic seizures in a woman with preeclampsia, not attributable to another cause. It is a neurological emergency treated with magnesium sulfate (which reduces seizure recurrence far better than phenytoin or diazepam), blood pressure control, and expedited delivery once the mother is stabilized.

HELLP syndrome (Hemolysis, Elevated Liver enzymes, Low Platelets) is a severe variant of preeclampsia and can occur even with normal blood pressure. It presents with right upper quadrant or epigastric pain, nausea, and malaise, and carries risk of hepatic rupture and disseminated intravascular coagulation. Management is the same principle as severe preeclampsia: stabilize and deliver.

Gestational Diabetes Mellitus (GDM)

Definition. GDM is glucose intolerance first recognized during pregnancy, typically identified through screening between 24 and 28 weeks.

Explanation. Pregnancy is a naturally insulin-resistant state — placental hormones such as human placental lactogen, progesterone, and cortisol antagonize insulin action to ensure a steady glucose supply to the fetus. In most women the pancreas compensates by increasing insulin secretion. GDM develops when beta-cell reserve cannot keep up with this rising resistance, so maternal glucose rises. Because glucose crosses the placenta freely but insulin does not, fetal hyperglycemia drives fetal hyperinsulinemia, which acts as a fetal growth hormone.

Example. A woman with a 1-hour 50 g glucose challenge test result of 145 mg/dL undergoes a 3-hour 100 g oral glucose tolerance test; two or more values exceed threshold, confirming GDM.

Real-world example. An obese woman with a strong family history of type 2 diabetes is screened early in the first trimester because of her risk factors (rather than waiting until 24–28 weeks), since she may have had undiagnosed pregestational diabetes.

Why it matters. Fetal hyperinsulinemia causes macrosomia (large-for-gestational-age baby), increasing risk of shoulder dystocia and birth trauma; after delivery, the sudden loss of maternal glucose supply while fetal insulin remains high causes neonatal hypoglycemia. GDM also increases the mother's lifetime risk of developing type 2 diabetes.

Common misunderstanding. Students often assume GDM babies are always born "sick" or small; in fact the classic finding is macrosomia, not growth restriction, because excess fetal insulin promotes fat and tissue deposition.

Ectopic Pregnancy

Definition. Ectopic pregnancy is implantation of a fertilized ovum outside the uterine cavity, most commonly (over 95% of cases) in the ampulla of the fallopian tube.

Explanation. Anything that slows or obstructs the fertilized egg's transit through the tube increases risk — prior pelvic inflammatory disease or tubal surgery, prior ectopic pregnancy, endometriosis, IUD use, and assisted reproduction. Because the tube cannot expand and support a growing pregnancy the way the uterus can, continued growth risks tubal rupture and intraperitoneal hemorrhage, a life-threatening emergency.

Example. A woman presents with 7 weeks of amenorrhea, unilateral pelvic pain, and light vaginal spotting. A urine pregnancy test is positive, but transvaginal ultrasound shows no intrauterine gestational sac.

Real-world example. A patient with a beta-hCG of 2,000 mIU/mL (above the discriminatory zone where an intrauterine pregnancy should be visible on transvaginal ultrasound) but an empty uterus on ultrasound is presumed to have an ectopic pregnancy until proven otherwise. If hemodynamically stable and unruptured, she may be treated medically with methotrexate; if ruptured or unstable, she needs emergency surgery (salpingostomy or salpingectomy).

Why it matters. Ectopic pregnancy is a leading cause of first-trimester maternal death due to hemorrhage from tubal rupture; rapid diagnosis (serial beta-hCG plus ultrasound) is essential.

Common misunderstanding. A negative urine pregnancy test essentially excludes ectopic pregnancy, but students sometimes wrongly assume vaginal bleeding rules it out — bleeding is often light or intermittent in ectopic pregnancy, unlike the heavier bleeding typical of miscarriage.

Placental Abnormalities

Placenta Previa

The placenta implants over or near the internal cervical os. The hallmark presentation is painless bright red vaginal bleeding, classically in the third trimester. Diagnosis is by ultrasound (transabdominal first, then transvaginal for precise localization — transvaginal ultrasound is safe despite previa). Digital vaginal examination is contraindicated because it can provoke severe hemorrhage. Management depends on gestational age and bleeding severity, ranging from expectant management with pelvic rest to scheduled cesarean delivery, since vaginal delivery risks catastrophic hemorrhage.

Placental Abruption

Premature separation of a normally implanted placenta from the uterine wall before delivery. Unlike previa, abruption presents with painful vaginal bleeding, uterine tenderness, and a firm, hypertonic uterus; bleeding may be concealed (retroplacental) and therefore appear less severe than the actual blood loss. Risk factors include hypertension (including preeclampsia), trauma, cocaine use, and prior abruption. It is a major cause of fetal distress and demands urgent evaluation, often emergency delivery.

Vasa Previa

Fetal vessels run through the membranes over the internal os, unprotected by placental tissue or umbilical cord. Rupture of membranes can tear these vessels, causing rapid fetal exsanguination — the classic exam clue is painless vaginal bleeding immediately after rupture of membranes accompanied by fetal heart rate abnormalities (since the blood lost is fetal, not maternal).

Key Terms

Term	Definition
Preeclampsia	New-onset hypertension after 20 weeks with proteinuria or evidence of end-organ dysfunction
Eclampsia	New-onset seizures in a woman with preeclampsia, not explained by another cause
HELLP syndrome	Hemolysis, Elevated Liver enzymes, Low Platelets — a severe preeclampsia variant
Gestational hypertension	New-onset hypertension after 20 weeks without proteinuria or organ dysfunction
Gestational diabetes mellitus (GDM)	Glucose intolerance first identified during pregnancy, usually via 24–28 week screening
Macrosomia	Fetus with estimated weight above the 90th percentile or over 4000–4500 g, often from fetal hyperinsulinemia
Ectopic pregnancy	Implantation of a fertilized ovum outside the uterine cavity, most often in the fallopian tube
Discriminatory zone	The beta-hCG level above which an intrauterine pregnancy should be visible on ultrasound if present
Placenta previa	Placenta implanted over or near the internal cervical os
Placental abruption	Premature separation of a normally implanted placenta before delivery
Vasa previa	Unprotected fetal vessels crossing the membranes over the internal os
Magnesium sulfate	Drug used for seizure prophylaxis and treatment in preeclampsia/eclampsia

Common Mistakes

Misconception	Why It's Wrong	Correct Understanding
"Preeclampsia is diagnosed by high blood pressure alone."	Hypertension alone after 20 weeks without proteinuria or organ dysfunction is gestational hypertension, not preeclampsia.	Preeclampsia requires hypertension plus proteinuria or another marker of end-organ dysfunction (low platelets, elevated creatinine, elevated liver enzymes, pulmonary edema, or new cerebral/visual symptoms).
"Painless bleeding in the third trimester is always placenta previa, and painful bleeding is always abruption."	While these are the classic teaching points, this is a helpful pattern rather than an absolute rule — some abruptions present with minimal pain, and previa can occasionally cause discomfort from contractions.	Use painless-vs-painful bleeding as your first clue, then confirm with ultrasound (which reliably identifies previa) and clinical findings (uterine tenderness/hypertonicity favors abruption).
"A GDM baby will be born small because the mother's blood sugar was poorly controlled."	This confuses GDM with conditions causing placental insufficiency; maternal hyperglycemia does the opposite.	Maternal glucose crosses the placenta and drives fetal hyperinsulinemia, which acts as a growth-promoting hormone, so the classic risk is macrosomia, not growth restriction.

Comparison and Connections

Feature	Placenta Previa	Placental Abruption
Pain	Painless	Painful, tender/hypertonic uterus
Bleeding	Bright red, may be recurrent	May be concealed; can seem less than actual blood loss
Diagnosis	Ultrasound (avoid digital exam)	Mainly clinical; ultrasound is insensitive
Key risk factor	Prior cesarean/uterine surgery, multiparity	Hypertension, trauma, cocaine use
Fetal risk	Preterm birth, hemorrhage at delivery	Fetal distress/hypoxia, stillbirth

Feature	Gestational Hypertension	Preeclampsia	Eclampsia
Onset	After 20 weeks	After 20 weeks	Preeclampsia + seizure
Proteinuria/organ damage	Absent	Present	Present
Seizures	No	No	Yes
Definitive treatment	Monitoring, may resolve	Delivery	Stabilize (MgSO4) then deliver

Practice Questions

Recall

1. What two features, besides hypertension, define preeclampsia? Answer guidance: proteinuria (≥300 mg/24 hr or equivalent), or in its absence, evidence of new end-organ dysfunction such as thrombocytopenia, renal insufficiency, impaired liver function, pulmonary edema, or new cerebral/visual symptoms.
2. Where does an ectopic pregnancy most commonly implant? Answer guidance: the ampulla of the fallopian tube (over 95% of ectopic pregnancies are tubal).

Understanding

3. Explain why preeclampsia causes proteinuria, headaches, and epigastric pain despite being fundamentally a "blood pressure" disorder. Answer guidance: abnormal placentation releases anti-angiogenic factors (e.g., sFlt-1) causing widespread maternal endothelial dysfunction — glomerular injury causes proteinuria, cerebral vasospasm/edema causes headache and visual changes, and hepatic capsule swelling causes epigastric pain. It is a multisystem endothelial disease, not isolated hypertension.
4. Explain why gestational diabetes typically causes macrosomia rather than a growth-restricted fetus. Answer guidance: maternal hyperglycemia crosses the placenta; the fetal pancreas responds with hyperinsulinemia, and insulin acts as a potent fetal growth factor, promoting fat and tissue deposition.

Application

5. A 34-year-old G2P1 at 38 weeks presents with sudden painful vaginal bleeding, a rigid tender uterus, and a non-reassuring fetal heart tracing. She has a history of chronic hypertension. What is the most likely diagnosis and immediate concern? Answer guidance: placental abruption; the immediate concern is fetal hypoxia/distress and maternal hemorrhage/DIC, requiring urgent delivery.
6. A 29-year-old with 6 weeks of amenorrhea presents with unilateral pelvic pain and a beta-hCG of 2,500 mIU/mL, but transvaginal ultrasound shows an empty uterus. What is the leading diagnosis and next step? Answer guidance: ectopic pregnancy is presumed since beta-hCG is above the discriminatory zone with no intrauterine sac visible; next steps include close monitoring with serial beta-hCG/ultrasound or treatment (methotrexate if stable and unruptured, surgery if ruptured/unstable).

Analysis

7. Compare and contrast placenta previa and vasa previa in terms of what actually bleeds and why this distinction matters clinically. Answer guidance: in previa, maternal blood vessels within the abnormally located placenta bleed; in vasa previa, unprotected fetal vessels rupture, so even small blood loss can be fetal exsanguination — hence vasa previa is a fetal emergency out of proportion to visible blood volume.
8. A patient with preeclampsia without severe features at 34 weeks is being monitored expectantly. What clinical or laboratory changes would prompt you to reclassify her as having severe preeclampsia and move toward delivery? Answer guidance: severe range blood pressure (≥160/110), thrombocytopenia, rising creatinine, elevated liver enzymes with symptoms, pulmonary edema, or new headache/visual disturbance unresponsive to treatment — any of these indicate progression and favor delivery over continued expectant management.

FAQ

1. Is preeclampsia curable during pregnancy? No. The only definitive cure is delivery of the placenta. Medications (antihypertensives, magnesium sulfate) manage symptoms and prevent seizures but do not reverse the underlying disease.

2. Can gestational diabetes go away after delivery? In most women, glucose tolerance normalizes after delivery because the placenta (the source of the insulin-antagonist hormones) is removed. However, these women carry a significantly increased lifetime risk of developing type 2 diabetes and should be rescreened postpartum.

3. Why is digital vaginal examination avoided in suspected placenta previa? Because the cervix and lower uterine segment are covered by placental tissue, a digital exam can dislodge the placenta and provoke sudden, severe hemorrhage. Diagnosis and monitoring rely on ultrasound instead.

4. How is an ectopic pregnancy treated if caught early? If the patient is hemodynamically stable, the ectopic mass is small, and there's no fetal cardiac activity, methotrexate (which stops trophoblastic cell division) can be used instead of surgery, with close beta-hCG follow-up to confirm resolution.

5. Why does magnesium sulfate specifically get used for eclampsia instead of standard anti-seizure drugs? Clinical trials have shown magnesium sulfate reduces the risk of recurrent seizures in eclampsia more effectively than phenytoin or diazepam, and it also has a favorable safety profile in pregnancy; its exact anticonvulsant mechanism in this setting is still debated but likely involves cerebral vasodilation and NMDA receptor antagonism.

Quick Revision

• Preeclampsia = hypertension after 20 weeks + proteinuria or end-organ dysfunction; eclampsia = preeclampsia + seizures.
• HELLP = Hemolysis, Elevated Liver enzymes, Low Platelets — a severe preeclampsia variant that can occur with normal blood pressure.
• Definitive treatment for preeclampsia/eclampsia is delivery; magnesium sulfate is for seizure prophylaxis, not a cure.
• GDM is screened at 24–28 weeks (earlier if high risk); classic fetal complication is macrosomia, not growth restriction.
• Fetal hyperinsulinemia (from maternal hyperglycemia) drives macrosomia and predisposes to neonatal hypoglycemia after birth.
• Ectopic pregnancy: over 95% are tubal (ampulla); risk factors include prior PID, tubal surgery, and prior ectopic.
• Beta-hCG above the discriminatory zone with an empty uterus on ultrasound suggests ectopic pregnancy.
• Placenta previa = painless bleeding, diagnosed by ultrasound, digital exam contraindicated.
• Placental abruption = painful bleeding with a tender, hypertonic uterus; bleeding may be concealed.
• Vasa previa = painless bleeding right after rupture of membranes with fetal distress — the bleeding is fetal blood.
• Chronic hypertension predates pregnancy or 20 weeks; gestational hypertension arises after 20 weeks without proteinuria/organ dysfunction.
• Always treat unexplained pelvic pain plus a positive pregnancy test as possible ectopic pregnancy until ruled out.

Related Topics

Prerequisites

• Normal physiology of pregnancy (placental hormones, cardiovascular and metabolic adaptations)
• Basic reproductive anatomy of the uterus, fallopian tubes, and placenta

Related Topics

• Antenatal care and screening protocols
• Diabetes mellitus (pathophysiology of insulin resistance)
• Disseminated intravascular coagulation (DIC)

Next Topics

• Labor and delivery complications
• Postpartum hemorrhage
• Neonatal complications of maternal disease (hypoglycemia, respiratory distress syndrome)