Placenta previa


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Placenta previa


Male and female reproductive system disorders

Precocious puberty

Delayed puberty

Klinefelter syndrome

Turner syndrome

Androgen insensitivity syndrome

5-alpha-reductase deficiency

Kallmann syndrome

Male reproductive system disorders

Hypospadias and epispadias

Bladder exstrophy


Penile cancer


Benign prostatic hyperplasia

Prostate cancer


Inguinal hernia




Testicular torsion

Testicular cancer

Erectile dysfunction

Male hypoactive sexual desire disorder

Female reproductive system disorders


Ovarian cyst

Premature ovarian failure

Polycystic ovary syndrome

Ovarian torsion

Krukenberg tumor

Sex cord-gonadal stromal tumor

Surface epithelial-stromal tumor

Germ cell ovarian tumor

Uterine fibroid



Endometrial hyperplasia

Endometrial cancer


Cervical cancer

Pelvic inflammatory disease


Female sexual interest and arousal disorder

Orgasmic dysfunction

Genito-pelvic pain and penetration disorder


Fibrocystic breast changes

Intraductal papilloma

Phyllodes tumor

Paget disease of the breast

Breast cancer

Hyperemesis gravidarum

Gestational hypertension

Preeclampsia & eclampsia

Gestational diabetes

Cervical incompetence

Placenta previa

Placenta accreta

Placental abruption



Potter sequence

Intrauterine growth restriction

Preterm labor

Postpartum hemorrhage


Congenital toxoplasmosis

Congenital cytomegalovirus (NORD)

Congenital syphilis

Neonatal conjunctivitis

Neonatal herpes simplex

Congenital rubella syndrome

Neonatal sepsis

Neonatal meningitis


Gestational trophoblastic disease

Ectopic pregnancy

Fetal hydantoin syndrome

Fetal alcohol syndrome

Reproductive system pathology review

Disorders of sex chromosomes: Pathology review

Prostate disorders and cancer: Pathology review

Testicular tumors: Pathology review

Uterine disorders: Pathology review

Ovarian cysts and tumors: Pathology review

Cervical cancer: Pathology review

Vaginal and vulvar disorders: Pathology review

Benign breast conditions: Pathology review

Breast cancer: Pathology review

Complications during pregnancy: Pathology review

Congenital TORCH infections: Pathology review

Disorders of sexual development and sex hormones: Pathology review

Amenorrhea: Pathology Review

Testicular and scrotal conditions: Pathology review

Sexually transmitted infections: Warts and ulcers: Pathology review

Sexually transmitted infections: Vaginitis and cervicitis: Pathology review

HIV and AIDS: Pathology review

Penile conditions: Pathology review


Placenta previa


0 / 6 complete

USMLE® Step 1 questions

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High Yield Notes

8 pages


Placenta previa

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USMLE® Step 1 style questions USMLE

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A 30-year-old woman, gravida 2 para 1, comes to the labor and delivery triage at 37 weeks gestation due to mild vaginal bleeding for the past 2 hours. She has not had any pain but has had occasional, non-painful contractions. She did not receive prenatal care but states that she took prenatal vitamins throughout the pregnancy. The patient’s firstborn was delivered via cesarean section. Temperature is 37.0°C (98.6°F), pulse is 100/min, and blood pressure is 115/80 mmHg. On physical examination, the patient appears comfortable. The uterus is soft and nontender. Streaks of blood are seen in the vaginal vault with no active bleeding. The fetus is in a vertex position. The fetal heart rate is 150 bpm. Which of the following is the most likely diagnosis? 

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Placenta previa p. 664


Content Reviewers

Rishi Desai, MD, MPH


Tanner Marshall, MS

Placenta previa means “placenta first,” because the placenta is the first thing within the uterine cavity.

In this condition, the placenta implants in the lower uterus, close to or even covering the uterine opening, called the internal cervical os, and it can therefore easily bleed, which usually happens after 20 weeks of gestation.

Normally the placenta implants in the upper uterus, and it's unclear why it implants in the lower uterus.

One hypothesis is that the placenta implants lower down when the endometrium in the upper uterus is not well vascularized.

In fact, endometrial damage from things like a previous cesarean section, an abortion (which could be induced or spontaneous), uterine surgery, and multiparity or multiple pregnancies can decrease vascularization and increase the risk of placenta previa.

In other cases, risk factors for placenta previa include having multiple placentas or a placenta with a larger than normal surface area, which can both happen with twins or triplets, as well as maternal age of 35 years or more, intrauterine fibroids, and maternal smoking.

Placenta previa is classified by how close the placenta is to the cervical os, it can be complete where the placenta completely covers the cervical os; partial where the placenta partially covers the cervical os; or marginal where the edge of the placenta extends to within 2 cm of the cervical os.

As the pregnancy progresses, the lower uterine segment grows, and if the placenta’s in the lower uterus, this growth disrupts the placental blood vessels, which can cause bleeding.

This usually a sudden onset of painless bright red bleeding that typically happens after 20 weeks gestation.


Placenta previa is a pregnancy complication in which the placenta implants in the lower uterus and partially or fully covers the internal cervical os, making vaginal delivery difficult or impossible. It can cause heavy vaginal bleeding and a serious threat to both the mother and the fetus. Symptoms include painless vaginal bleeding in the third trimester, and some risk factors are previous placenta previa, multiple gestation, and uterine fibroids.


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