Miscarriage Risk for Asymptomatic Women After a Normal First-Trimester Prenatal Visit

Abstract

OBJECTIVE: 

To estimate the risk of miscarriage among asymptomatic women after a prenatal visit between 6 and 11 weeks of gestation where proof of fetal viability of a singleton was obtained by office ultrasonography at the same visit.

METHODS: 

This was a prospective cohort study performed over 2 years (March 2004–2006) at an antenatal clinic at a large tertiary hospital in Victoria, Australia. Those recruited were 697 asymptomatic women who attended their first antenatal visit between 6 (+2 days) and 11(+6 days) weeks of gestation, where evidence of fetal cardiac activity of a singleton was obtained by office ultrasonography. The main outcome measure was rates of miscarriage, stratified by gestation at presentation.

RESULTS: 

One case was lost to follow-up. The risk of miscarriage among the entire cohort was 11 of 696 (1.6%). The risk fell rapidly with advancing gestation; 9.4% at 6 (completed) weeks of gestation, 4.2% at 7 weeks, 1.5% at 8 weeks, 0.5% at 9 weeks and 0.7% at 10 weeks (χ²; test for trend P=.001). Most who miscarried received their ultrasound diagnoses many weeks after their visit; five (45%) were diagnosed in the second trimester, and all but one received their ultrasound diagnoses after 10 weeks of gestation.

CONCLUSION: 

For women without symptoms, the risk of miscarriage after attending a first antenatal visit between 6 and 11 weeks is low (1.6% or less), especially if they present at 8 weeks of gestation and beyond. Our data could be used to reassure such women that the probability of progressing to later than 20 weeks of gestation is very good.

LEVEL OF EVIDENCE: 

III

In Brief

For asymptomatic women attending a prenatal visit between 8 and 11 weeks of gestation with an office ultrasonogram confirming viability, the risk of miscarriage is less than or equal to 1.5%.