Pregnancy: Likelihood Ratios

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The likelihood ratios of findings for Pregnancy are listed below. See the left navigation bar to change the display.

Pre-Test Probability (Prevalence): %.	Post-Test Probability (Predictive Value): %.	Switch to display mode.
Note that calculating probabilities from more than one** finding is inherently inaccurate because findings are not independent. (For example, using two positive findings that share a common pathogenesis is likely to overestimate the true probability.)


Finding	Result	+LR	-LR
[ + ] Any Pregnancy Symptoms	+ 0 -	2.4	0.6
morning sickness, breast tenderness / fullness, urinary frequency, or fatigue Study: JAMA. 1997 Aug 20;278(7):586-91. PMID: 9268281
[ + ] Breast Signs on Exam	+ 0 -	2.7	0.6
not specifically defined Study: JAMA. 1997 Aug 20;278(7):586-91. PMID: 9268281
[ + ] Chadwick Sign	+ 0 -	25.5	0.5
Only 1 study from Dr Chadwick. Sign is "characteristic" deep violet-blue color of anterior vaginal wall. Rarely seen before 7 weeks. Study: JAMA. 1997 Aug 20;278(7):586-91. PMID: 9268281
[ + ] Delayed Menses	+ 0 -	1.1	0.8
Study: JAMA. 1997 Aug 20;278(7):586-91. PMID: 9268281
[ + ] Did Not Use Birth Control	+ 0 -	1.5	0.3
Study: JAMA. 1997 Aug 20;278(7):586-91. PMID: 9268281
[ + ] Goodell's Sign		No accuracy specified.
softening of the cervix, may be detected by 8 weeks of age Study: JAMA. 1997 Aug 20;278(7):586-91. PMID: 9268281
[ + ] Hegar's Sign		No accuracy specified.
Softening of the lower portion of the corpus of the uterus. May be seen by 6 weeks. Study: JAMA. 1997 Aug 20;278(7):586-91. PMID: 9268281
[ + ] Home Pregnancy Test		Sensitivity = 75%
Sens = 75% when used by actual patients but up to 91% when used by volunteers. Specificity not assessed but should be very high (~99%). Study: Arch Fam Med 1998 Sep-Oct;7(5):465-9. PMID 9755740
[ + ] Morning Sickness	+ 0 -	2.7	0.7
Study: JAMA. 1997 Aug 20;278(7):586-91. PMID: 9268281
[ + ] Palpable Fundus	+ 0 -	2.8	0.9
Study: JAMA. 1997 Aug 20;278(7):586-91. PMID: 9268281
[ + ] Patient Thinks She is Pregnant	+ 0 -	2.1	0.4
Study: JAMA. 1997 Aug 20;278(7):586-91. PMID: 9268281
[ + ] Serum beta-hCG	+ 0 -	inf	0
as compared to urine beta hCG, for all comers to an ED for whom pregnancy tests were ordered. In this study, urine beta hCG had sens = 100%, spec = 99.2% Study: Am J Emerg Med. 1993 Jul;11(4):434-6. PMID: 8216535
[ + ] Trans-Vaginal Ultrasound		No accuracy specified.
Gestational sac by 4.5-5 weeks, double decidual sign by 5.5-6 weeks, yolk sac by 5-6 weeks, cardiac activity by 5.5-6 weeks. Trans-abdominal ultrasound would be less sensitive for these findings. Study: UpToDate http://www.utdol.com/online/content/topic.do?topicKey=antenatl/22517
[ + ] Urine beta-hCG		Sensitivity = 90%
on 1st day of missed period. Most urine b-hCG tests are sensitive to 20 mIU/ml. If sensitivity is at 0.5 mIU/ml then should be sensitive by 7 days after fertilization. Study: JAMA 2001 Oct 10;286(14):1759-61. PMID 11594902
[ + ] Urine beta-hCG		Sensitivity = 97%
7 days after missed period. Most urine b-hCG tests are sensitive to 20 mIU/ml. If sensitivity is at 0.5 mIU/ml then should be sensitive by 7 days after fertilization. Study: JAMA 2001 Oct 10;286(14):1759-61. PMID 11594902
[ + ] Uterine Artery Pulsation	+ 0 -	11	0.3
only 1 study Study: JAMA. 1997 Aug 20;278(7):586-91. PMID: 9268281
[ + ] Vaginal Exam Signs	+ 0 -	3.2	0.9
not explicitly defined Study: JAMA. 1997 Aug 20;278(7):586-91. PMID: 9268281