PREGNANCY CONFIRMATION AND DATING
- High sensitivity urine pregnancy test (HSPT):
- Widely available, inexpensive urine tests 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 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 determine EGA as range in level is wide & variable for any GA
- Serial measurements often used to evaluate suspected ectopic, abortion completion (i.e. when products of conception are not visualized following aspiration), or in management of molar pregnancy
- Other hCG assays in limited availability and use in the United States:
- Low sensitivity urine test (detects hCG of at least 1000-2000 mIU/mL)
- Multi-level pregnancy test (MLPT; a urine test measuring hCG levels within specified ranges).
LAST MENSTRUAL PERIOD (LMP)
- Providers can confidently use clinical dating (LMP +/- exam) for most patients with known LMP to determine eligibility for abortion type and setting.
- 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 to 8 weeks LMP (Kapp 2020, Ipas 2021, Macaulay 2019, Raymond 2015, Schonberg 2014).
- In settings where US access is limited, LMP maintains high accuracy for abortions performed at or above 13 weeks (Kapp 2020, Ipas 2021, WHO 2022).
- Of note, while asking history of irregular periods and hormonal use may increase specificity of accurate dating, it also increases false negatives, resulting in unneccessary ultrasounds for patients that were in fact eligible for medication abortion (Ralph 2021).
- Using medical history alone including LMP dating for medication abortion has high rates of safety and efficacy up to 10-11 weeks LMP (Upadhyay 2022).
- If LMP is unknown, a series of questions (Are you >10 weeks pregnant? Have you missed >2 periods? Are you >2 months pregnant?) may be used to determine eligibility for medication abortion. (Ralph 2021).
|Bimanual exam may improve estimation of gestational age over LMP alone|
|Dating by uterine size in centimeters||
|Dating by uterine size in fruit comparisons||lemon
|Limitations of bimanual sizing:
*Consider US guidance or additional management