Table 2-1. Risk Factors for Ectopic Pregnancy



 

Scarring or Adhesions Obstructing Normal Zygote Migration

     
Infectious   Pelvic inflammatory disease
     
Postsurgical   Tuboplasty/ligation
     
Congenital   Diethylstilbestrol
     
Idiopathic   No risk factors
     

 

Clinical Findings

 

Symptoms. The classic triad with an unruptured ectopic pregnancy is amenorrhea,vaginal bleeding, and unilateral pelvic-abdominal pain. With a ruptured ectopic preg-nancy, the symptoms will vary with the extent of intraperitoneal bleeding and irritation. Pain usually occurs after 6–8 menstrual weeks.

 

Signs. The classic findings with an unruptured ectopic pregnancy are unilateraladnexal and cervical motion tenderness. Uterine enlargement and fever are usually absent. With a ruptured ectopic pregnancy, the findings reflect peritoneal irritation and the degree of hypovolemia. Hypotension and tachycardia indicate significant blood loss. This results in abdominal guarding and rigidity.

 

Investigative findings. Ab-hCG test will be positive. Sonography may or may notreveal an adnexal mass, but most significantly no intrauterine pregnancy (IUP) will be seen.

Diagnosis. The diagnosis of an unruptured ectopic pregnancy rests on the results of a quanti-tative serum b-hCG titer combined with the results of a vaginal sonogram. It is based on the assumption that when a normal intrauterine pregnancy has progressed to where it can be seen on vaginal sonogram at 5 weeks’ gestation, the serum b-hCG titer will exceed 1,500 mIU. With the lower resolution of abdominal sonography, an IUP will not consistently be seen until 6 weeks’ gestation. The b-hCG discriminatory threshold for an abdominal ultrasound to detect an intrauterine gestation is 6,500 mIU compared with 1,500 mIU for vaginal ultrasound.

 

Specific criteria. Failure to see a normal intrauterine gestational sac when the serumb-hCG titer is >1,500 mIU is presumptive diagnosis of an ectopic pregnancy.

 

Diagnosis of unruptured ectopic pregnancy is presumed when:

 

b-hCG titer >1,500 mIU

 

No intrauterine pregnancy is seen with vaginal sonogram

Management

 

Ruptured ectopic. The diagnosis of ruptured ectopic pregnancy is presumed witha history of amenorrhea, vaginal bleeding, and abdominal pain in the presence of a

 

hemodynamically unstable patient. Immediate surgical intervention to stop the bleed-ing is vital, usually by laparotomy.

 

Intrauterine pregnancy. If the sonogram reveals an IUP, management will be basedon the findings. If the diagnosis is hydatidiform mole, the patient should be treated with a suction curettage and followed up on a weekly basis with b-hCG.

 

 

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Chapter 2 l Failed Pregnancy

 

 

Possible ectopic. If the sonogram does not reveal an IUP, but the quantitativeb-hCG is <1,500 mIU, it is impossible to differentiate a normal IUP from an ectopic pregnancy. Because b-hCG levels in a normal IUP double every 58 hours, the appropriate management will be to repeat the quantitative b-hCG and vagi-nal sonogram every 2–3 days until the b-hCG level exceeds 1,500 mIU. With that information an ectopic pregnancy can be distinguished from an IUP.

 

Unruptured ectopic. Management can be medical with methotrexate or surgical withlaparoscopy. Medical treatment is preferable because of the lower cost, with otherwise similar outcomes.

 

Methotrexate. This folate antagonist attacks rapidly proliferating tissues includ-ing trophoblastic villi. Criteria for methotrexate include pregnancy mass <3.5 cm diameter, absence of fetal heart motion, b-hCG level <6,000 mIU, and no history of folic supplementation. Single dose 1 mg/kg is 90% successful. Patients with an ectopic pregnancy should be advised of the somewhat increased incidence of recur-

 

rent ectopic pregnancies. Follow-up with serial b-hCG levels is crucial to ensure pregnancy resolution. Rh-negative women should be administered RhoGAM.

 

Laparoscopy. If criteria for methotrexate are not met, surgical evaluation is per-formed through a laparoscopy or through a laparotomy incision. The preferred procedure for an unruptured ampullary tubal pregnancy is a salpingostomy, in which the trophoblastic villi are dissected free preserving the oviduct. Isthmic tubal pregnancies are managed with a segmental resection, in which the tubal segment containing the pregnancy is resected.

 

Salpingectomy is reserved for the patient with a ruptured ectopic pregnancy or those with no desire for further fertility. After a salpingostomy b-hCG titers should

be obtained on a weekly basis to make sure that there is resolution of the pregnancy. Rh-negative women should be administered RhoGAM.

 

Follow-Up. Patients who are treated with methotrexate or salpingostomy should be followed upwith b-hCG titers to assure there has been complete destruction of the ectopic trophoblastic villi.

 

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Obstetric Procedures

 

 

OBSTETRIC ULTRASOUND

This imaging modality uses low-energy, high-frequency sound waves.

 

 

MODALITIES

 

Transvaginal sonogram: used in first trimester, producing high-resolution imagesthat are not influenced by maternal BMI. Dating accuracy of first trimester sonogram is +/- 5 days.

 

Transabdominal sonogram: used any time during the pregnancy, but image quality maybe limited by maternal obesity. No adverse fetal effects have been noted during decades of research studies. Dating accuracy of early second trimester sonogram is +/- 7-10 days.

 

Doppler ultrasound studies: used to assess umbilical artery (UA) and middle cerebralartery (MCA) blood flow. This modality assesses fetal well-being in IUGR pregnancies as well as fetal anemia in alloimmunized pregnancies.

Indications for obstetrical ultrasound include:

 

• Pregnancy location & viability, gestational age dating

 

• Multiple gestation (zygosity, chorionicity, amnionicity)

 

• Amniotic fluid volume (oligohydramnios, polyhydramnios)

 

• Fetal growth (IUGR, macrosomia)

 

• Fetal anomalies, fetal well-being

 

• Pregnancy bleeding, fetal anemia

 

Genetic sonogram, ideally performed at 18-20 weeks, looks for anatomic markers of fetalaneuploidy which includes:

 

Generic: any structural abnormalities

 

Specific: nuchal skin fold thickness (strongest predictor), short long bones, pyelectasis,echogenic intracardiac focus, hyperechoic bowel.

 

Nuchal translucency (NT) measurement is a screening test, performed between 10-14 weeks,measuring the fetal fluid collection behind the neck.

 

• A thickened NT increases the likelihood of aneuploidy and cardiac disease.

 

• It is combined with two maternal blood tests (free b-hCG & PAPP-A) in first-trimester screening to increase the sensitivity and specificity for aneuploidy screening.


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USMLE Step 2 l Obstetrics

 

 


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