Case 43: Early pregnancy ultrasound

 

Case 43: Early pregnancy ultrasound

CASE 43: EARLY PREGNANCY ULTRASOUND

History

A 25-year-old woman is referred by the general practitioner (GP) for early pregnancy dating

ultrasound scan. She is gravida 4 para 2. Her first positive pregnancy test was 4 days ago and

she went to her GP to arrange a termination of pregnancy as she feels that she cannot cope

with another child. She has been taking the combined oral contraceptive pill (COCP), so

pregnancy could not be dated clinically. She has no significant gynaecological history of note

except for an episode of chlamydia at age 18 years, for which she and her partner were fully

treated. As a child she had a ruptured appendix and needed a midline laparotomy. She has no

other relevant past medical history.

She has had no pain though did note some moderate vaginal bleeding 2 weeks before for 3

days, which settled spontaneously.

Examination

She looks well with normal heart rate and blood pressure and a soft non-tender abdomen.

Speculum examination shows a closed cervix with a normal discharge and no blood. The

uterus feels normal size and is anteverted and mobile. There is no cervical excitation. There is

slight tenderness in the left adnexa but no masses are palpable.

INVESTIGATIONS

Transvaginal ultrasound findings are shown in Fig. 43.1.

Questions

• How would you interpret this ultrasound scan result?

• Serial serum human chorionic gonadotrophin (hCG) and progesterone are requested

and the results are as follows:

Day 1: serum hCG 703 IU/L, progesterone 30 nmol/L

Day 3: serum hCG 905 IU/L, progesterone 24 nmol/L

• What is the likely diagnosis and the differential diagnosis, and how would you further investigate and manage this woman?

Figure 43.1 Transvaginal ultrasound

scan showing a midsagittal view of

the uterus.100 Cases in Obstetrics and Gynaecology

108

ANSWER 43

The transvaginal ultrasound scan shows an empty uterus and no adnexal masses. This is

therefore termed a pregnancy of unknown location (PUL).

! Definition of a pregnancy of unknown location

No ultrasound signs of either intra- or extrauterine pregnancy or retained products of

conception in a woman with a positive pregnancy test

PUL occurs in up to 20 per cent of women in early pregnancy units and the possible underlying diagnoses are:

• early intrauterine pregnancy: too early to be visualized on ultrasound

• failed pregnancy: a complete miscarriage where the pregnancy has been completely

expelled but where no previous scan is available to confirm that an intrauterine

pregnancy had been present

• ectopic pregnancy: the pregnancy is located outside the uterine cavity but has not

been visualized at initial ultrasound examination.

Only 10 per cent of PULs are subsequently diagnosed as ectopic pregnancies, but all must be

investigated with serial serum hCG to determine which of the above three diagnoses is likely.

Serum hCG results and management

The hCG at which an intrauterine pregnancy would normally be visualized is 1000–1500

IU/L (in most but not all cases). A normal early pregnancy would generally show an increase

in hCG of over 66 per cent in each 48 h. The progesterone level is usually high (40–60 nmol/L)

in an ongoing pregnancy and low (<20 nmol/L) in a failing pregnancy.

In this case the suboptimal hCG rise and midrange progesterone are typical (but not diagnostic) of an ectopic pregnancy, and the woman should have a repeat ultrasound within a

few days. If an ectopic pregnancy is visualized then medical or surgical management should

depend on signs and symptoms. If a pregnancy is still not visualized and she becomes

symptomatic then laparoscopy is indicated to establish the diagnosis. If hCG continues

to rise with no apparent pregnancy visible, then methotrexate for persistent PUL may be

considered.

KEY POINTS

• Pregnancy of unknown location may represent an early intrauterine pregnancy,

complete miscarriage or an ectopic pregnancy.

• Follow-up hCG and ultrasound must be arranged for these women.

• If pain develops before a diagnosis is confirmed, laparoscopy should be carried

out to exclude an ectopic pregnancy.