.A healthy 33-year-old grandmultiparous housewife
(Madam Z) booked in Singapore General Hospital
antenatal clinic at 22 weeks gestation. She has
previously undergone 6 normal vaginal deliveries,
and 1 elective caesarean section for breech. Booking
investigations and parameters were normal. Screening
scan showed parameters equal to dates and no foetal
abnormalities. However, placenta was noted to be
lower posterior reaching cervical os. Subsequent
growth scan at 26 weeks was satisfactory, but placenta
was still low-lying.
At 31 weeks gestation, patient presented to the
labour ward for 1 day history of painless, mild
antepartum haemorrhage. Foetal movement was
satisfactory. Upon admission, blood pressure
was 128/68mmHg and pulse rate was 80 beats per
minute. Uterus felt soft with no contractions and
non-tender. Lie of the foetus was longitudinal and
presentation cephalic. Speculum showed a closed
cervical os. Foetal well-being was confirmed by
a reactive cardiotocograph.
Ultrasound showed a type 3 posterior placenta
praevia with tip reaching cervical os. There were
small vessels crossing the internal os, raising the
suspicion of vasa praevia. There were no retroplacental
clots and estimated foetal weight 1,997gm.
Differential diagnosis included vasa praevia and
umbilical cord overlying the cervical os. Repeat
scan an hour later excluded the possibility of
umbilical cord lying above the cervical os, thereby
increasing the likelihood of vasa praevia (see Fig. 1,
overleaf). Doppler study was used to confirm the
presence of vessels.
Haemoglobin was 10.1g/dl and coagulation
screen normal. Oral nifedipine for tocolysis and
intramuscular betamethasone to improve foetal
lung maturity was administered in anticipation
of a preterm delivery should a massive antepartum
haemorrhage occur. Patient had only minimal
per vaginal staining during her 3-day inpatient
stay and subsequently discharged against
medical advice.
Madam Z defaulted subsequent antenatal followup
and presented 1 month later at 36 weeks
gestation with a second episode of painless
antepartum haemorrhage, soaking 3 pads.
Cardiotocograph demonstrated a reactive trace and
weak irregular uterine contractions. Admission
haemoglobin was 11.5g/dl and coagulation screen
normal. Patient underwent an emergency caesarean