Preterm birth (PTB) is a major challenge to perinatal health. It is defined as delivery
before 37 completed gestational weeks. It accounts for 75% of perinatal deaths and more than
50% of long-term neurological disabilities, and it is the second most common cause of death
in children under the age of 5 year. Neonates born preterm are at risk of respiratory
distress syndrome, chronic lung disease, retinopathy of prematurity, necrotizing
enterocolitis, intraventricular haemorrhage and sepsis in the short term, as well as cerebral
palsy, motor and sensory impairment, learning difficulties, and increased risk of chronic
disease in long run. It is estimated that the societal cost of PTB is $26 billion annually in
the USA alone.
Until now, prevention or reduction of PTB is based on identification of risk factors in
obstetrical history, biochemical markers and short cervix. History of PTB and asymptomatic
short cervix at the second trimester are both strong predictors for PTB. In women with
asymptomatic short cervix at the second trimester, vaginal progesterone could effectively
reduce PTB. Universal cervical length screening followed by treatment with vaginal
progesterone has been shown to be the most cost effective strategy in preventing PTB. These
findings were confirmed in meta-analysis.
Nevertheless, only minority of women may benefit from progesterone treatment if it was being
started at the second trimester. There is still a large proportion of PTB, which is currently
not preventable, and the current approach to prevent PTB is far from ideal.
One possible hypothesis is that the initiation of progesterone treatment would be too late
for its effect to take place. Therefore, we decide to use oral progesterone in the current
study. The objective of the study is to determine whether early use of progesterone can
prevent PTB better when compared with universal screening of cervical length and followed by
treatment with progesterone in those with short cervix.