Association between low day 16 hCG and miscarriage after proven cardiac activity

To investigate an association between low human chorionic gonadotrophin (hCG) levels at the end of the first week of implantation and later clinical miscarriage occurring after ultrasound confirmation of a live pregnancy.

This was an observational retrospective study of 1,054 women who underwent in vitro fertilization and achieved an ultrasound-confirmed live singleton pregnancy with cardiac activity. The incidence of miscarriage diagnosed at 8-19 weeks +6 days of gestation was estimated in these 3 subgroups according to their hCG concentrations at day 16 after conception: less than the 25th, 25th-75th, and more than the 75th percentiles.

The overall incidence of miscarriage was 11.1% (117/1,054), and the median gestational age at diagnosis was 10 weeks and 4 days. The median (95% confidence interval) day 16 hCG level in the miscarriage group was 182 mIU/mL (157-211), significantly lower than the median level in those who had an ongoing pregnancy (223 mIU/mL [213-233], P < .003). There was an increasing risk of miscarriage associated with decreased hCG levels (8.0% at > 75th percentile; 9.9% at 25th-75th percentiles; 16.7% at < 25th percentile; P = .003).

Low hCG levels in very early pregnancy are associated with an increased risk of miscarriage occurring after the clinical recognition of pregnancy. The mechanisms underlying late first-trimester and second-trimester miscarriages may have begun as early as the first week of implantation.

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