Controversies about the Secondary Prevention of Spontaneous Preterm Birth

Abstract

Preterm birth is one of the major global health problems and part of the Millennium Development goals because of the associated high number of perinatal or neonatal mortality and long-term risks of neurodevelopmental and metabolic diseases. Transvaginal sonography has meanwhile been established as a screening tool for spontaneous preterm birth despite its relatively low sensitivity when considering only the cervical length. Vaginal progesterone has been shown to reduce prematurity rates below 34 weeks in a screening population of singleton pregnancies. Up to now, no positive long-term effect could be demonstrated after 2 years. It seems to have no benefit to prolong pregnancies after a period of preterm contractions and in risk patients without cervical shortening. Meta-analyses still demonstrate conflicting results dependent on quality criteria used for selection. A cerclage is only indicated in singleton pregnancies with previous spontaneous preterm birth and a combined cervical shortening in the current pregnancy. Nevertheless, the short- and long-term outcome has never been evaluated, whereas maternal complications may be increased. There is no evidence for a prophylactic cervical cerclage in twin pregnancies even in cases with cervical shortening. Emergency cerclage remains an indication after individual counseling. The effect of a cervical pessary in singleton pregnancy seems to be more pronounced in studies where a few investigators with increasing experience have treated and followed the patients at risk for preterm birth. Mainly in twin pregnancies, pessary treatment seems to be promising compared to other treatment options of secondary prevention when the therapy is started at early stages of precocious cervical ripening. At present, several international trials with the goal to reduce global rates of prematurity are in progress which will hopefully allow to specify the indications and methods of intervention for certain subgroups. When trials are summarized, prospective meta-analyses carry a lower risk of bias than the meanwhile uncontrolled magnitude of retrospective meta-analyses with conflicting results.

Zusammenfassung

Frühgeburten gehören zu den wichtigsten Gesundheitsproblemen weltweit und gehören wegen der damit verbundenen hohen perinatalen und neonatalen Mortalitätsraten und der Langzeitrisiken für neurologische Entwicklungsstörungen und Stoffwechselkrankheiten zu den Millenniums-Entwicklungszielen. Obwohl die Sensitivität der transvaginalen Sonografie bei der Messung der zervikalen Länge relativ niedrig ist, hat sich diese Methode als Screeninginstrument bei der Prävention von spontanen Frühgeburten etabliert. Die vaginale Verabreichung von Progesteron hat in einer Population werdender Mütter mit Einlingsschwangerschaft die Frühgeburtsraten vor der 34. Woche nachweislich verringert. Bislang wurden aber keine positiven Langzeitwirkungen nach 2 Jahren nachgewiesen. Es scheint, dass die Herauszögerung der Schwangerschaft nach einiger Zeit mit vorzeitigen Wehen sowie bei Risikopatientinnen ohne Zervixverkürzung keine Vorteile bietet. Die Ergebnisse von Metaanalysen sind nach wie vor widersprüchlich und hängen von den gewählten Qualitätskriterien ab. Eine Cerclage ist nur bei Einlingsschwangerschaften nach spontaner Frühgeburt in einer vorherigen Schwangerschaft verbunden mit einer Zervixverkürzung in der aktuellen Schwangerschaft indiziert. Die kurz- und langfristigen Auswirkungen wurden nicht untersucht, obwohl sie möglicherweise zu einer Erhöhung der mütterlichen Komplikationen führen könnten. Es gibt keine Hinweise, dass die prophylaktische zervikale Cerclage vorteilhaft ist bei Zwillingsschwangerschaften, selbst bei Frauen mit Zervixverkürzung. Je nach individueller Beratung mag eine Not-Cerclage indiziert sein. Die Wirkung eines zervikalen Pessars in Einlingsschwangerschaften war ausgeprägter in Studien, bei denen die Untersucher zunehmende Erfahrung hatten bei der Behandlung und Nachbetreuung von Frauen mit einem höheren Risiko für Frühgeburtlichkeit. Im Vergleich zu anderen Optionen für die Sekundärprävention scheint die Behandlung mit einem Pessar erfolgversprechend, vor allem bei Zwillingsschwangerschaften, wenn früh mit der Behandlung begonnen wird, d. h. in den ersten Stadien einer vorzeitigen Zervixreifung. Zurzeit laufen mehrere internationale Studien, die alle das Ziel haben, die Frühgeburtsraten weltweit zu reduzieren, und die hoffentlich weitere Hinweise auf die Indikationen und Interventionsmethoden für bestimmte Untergruppen liefern werden. Bei der Zusammenfassung von Studien wiesen prospektive Metaanalysen ein niedrigeres Verzerrungsrisiko auf als die inzwischen unkontrollierte Menge retrospektiver Metaanalysen mit ihren widersprüchlichen Ergebnissen.

Key words

preterm birth - cervical shortening - progesterone - cerclage - pessary

Schlüsselwörter

Frühgeburt - Zervixverkürzung - Progesteron - Cerclage - Pessar

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