PREGNANCY CONFIRMATION AND DATING


PREGNANCY TESTS

  • High sensitivity urine pregnancy test (HSPT):
    • Widely available, inexpensive urine test available over the counter or in clinics.
    • Simple, accurate qualitative test detecting hCG at concentrations of 20-25 mIU/mL.
    • Usually positive by cycle day 32-35 (95% of pregnancies). 
    • May remain positive for up to 4 or more weeks following an uncomplicated abortion.
    • May be used after 4 weeks to monitor for completion of a medication abortion.
  • Serum quantitative hCG test:
    • Available in clinics only with an order from a healthcare provider
    • Detects serum levels of hCG as low as 2-10 mIU/mL.
    • Not used to confirm pregnancy nor to determine EGA as level range is wide & variable for any GA.
    • Serial measurements often used to evaluate suspected ectopic, abortion completion (i.e. when products of conception not visualized following aspiration), or in management of molar pregnancy.
  • Other hCG assays in limited availability and use in United States:
    • Low sensitivity urine test (detects hCG of at least 1000-2000 mIU/mL)
    • Multi-level pregnancy test (MLPT; a graduated urine test).

LAST MENSTRUAL PERIOD (LMP)

  • Providers can safely use clinical dating (LMP +/- exam) for most patients with known LMP to determine eligibility for abortion type and setting, compared to the need to determine EDC for a patient continuing their pregnancy.
  • First day of LMP alone (+/- 1 week of certainty) is an accurate means of estimating gestational age, with low rates of under- or over- estimation through mid-first trimester (Raymond 2015, Macaulay 2019, Schonberg 2014, Bracken 2011).

BIMANUAL EXAM

Bimanual exam may improve estimation of gestational age over LMP alone
Dating by uterine size in centimeters
  • After 4 weeks, uterus increases by approximately 1 cm per week
  • After 12 weeks, uterus rises out of pelvis
  • At 15-16 weeks, uterus reaches midpoint between symphysis and umbilicus
  • At 20 weeks, uterus reaches umbilicus
  • After 20 weeks, fundal height from pubic symphysis in centimeters approximately equals weeks
Dating by uterine size in fruit comparisons lemon
medium orange
grapefruit
5-6 weeks
7-8 weeks
9-10 weeks
Limitations to bimanual sizing:
  • Abdominal scarring (multiple cesareans); less uterine mobility*
  • Fibroids*
  • Multiple gestations*
  • Uterine retroversion
  • Obesity

*Consider US guidance or additional management

uterus size by week

License

EARLY ABORTION TRAINING CURRICULUM Copyright © 2020 by UCSF Bixby Center for Global Reproductive Health. All Rights Reserved.