There are few things we can do to prevent preterm birth. One of the primary tools in the toolkit is progesterone. Mothers with a history of spontaneous preterm birth are at increased risk of a repeat preterm birth and are routinely prescribed progesterone to decrease this risk. Another group of women who benefit from progesterone therapy are women with a short cervical length. How would you know if someone has a short cervix? One way is to measure the cervical length with ultrasound- but who should get this ultrasound exam? Everyone? Just high-risk women? Is this strategy cost-effective? And, are women who are eligible even getting their treatment?
Three new studies in the July 2016 issue of AJOG focus on these questions about cervical length screening and progesterone therapy. The first study hails from researchers at the University of Utah and Northwestern University. We already know that women with a history of spontaneous preterm birth benefit from progesterone therapy, so the researchers focused only on women with no such history. They compared three different strategies for screening cervical length. Strategy 1 was universal screening, meaning that all pregnant women get an ultrasound to measure their cervical length. Strategy 2 was risk-based screening, in which only women with an elevated risk of preterm birth or shortened cervix receive the ultrasound exam. Finally, Strategy 3 was no screening.
Universal screening would include 3.5 million women with no history of preterm birth and an additional 11,027 women would theoretically be prescribed and receive progesterone. Assuming all of these women receive progesterone and it has the benefit we think it does, then there would be 913 fewer preterm births at less than 35 weeks and 63 fewer neonatal deaths (as compared to risk-based screening). How much would all this screening and treatment cost? The researchers estimate $62 billion. Guess how much they estimate no screening would cost? $62 billion. That’s due to all the additional complications from not treating with progesterone. Comparing all three strategies, the authors concluded that universal screening would prevent the most preterm births and also be the most cost effective given the complications progesterone treatment would prevent.
Now you’re probably thinking- well, that was easy! Let’s start doing ultrasound screening exams on every pregnant woman. Not so fast. The next study calls into question some of the basic assumptions from the first study. Researchers from the University of Alabama at Birmingham conducted a study that showed the importance of how we estimate progesterone effectiveness. Their analysis demonstrated that progesterone has to reduce preterm birth by at least 34% (in the best case scenario) to be cost effective. Existing data does not support such high efficacy, so these authors conclude that cervical length screening is not cost effective.
Ready to throw your hands up in defeat? To complicate matters even more, a third study revealed that even women who clearly need progesterone are not necessarily getting it. Researchers at the University of North Carolina, Chapel Hill, reviewed the records of all the women with a history of spontaneous preterm birth delivering at two hospitals. As I mentioned above, all of these women should have received progesterone because of their history. Of the 627 women who should have received progesterone shots, only 296 (47%) received at least 1 dose. Women who received the therapy received a median of 9 injections, although 28% of the charts didn’t include information on the number of doses received.
This last study reveals some very big gaps in our current knowledge about practices and what actually happens in the real world. The controversy is clearly still raging about whether or not we should institute universal cervical length screening. But- if we do- how will we ensure that everyone who needs progesterone actually gets it, especially when women who are eligible for it now are not getting it. We want to hear from you! Do you think all pregnant women should receive cervical length screening? How can we ensure more women get the progesterone treatment they need?