RESUMO
KEY CONTENT: Twin pregnancies are associated with a three-fold greater perinatal mortality than singleton pregnancies. Prematurity is a main contributor, with 50% of twin pregnancies delivering before 37 weeks and 10% delivering before 32 weeks of gestation.The aetiology of preterm delivery in twin pregnancies is likely multifactorial and different from that of singletons.Cervical cerclage reduces preterm birth rates in singletons but has mixed results in twins with some studies showing harm.The use of progesterone to prevent preterm birth in singletons has conflicting results and has not been proven to prevent preterm birth in twins. Studies continue to determine whether the cervical pessary is effective in preventing preterm birth in multiple pregnancies.There is a paucity of data available on the prevention of preterm birth in triplets/higher order multiples but similar principles to twin pregnancy apply. LEARNING OBJECTIVES: To review the burden of preterm birth in multiple pregnancy.To understand the methods available for preventing preterm birth in multiple pregnancies and the evidence surrounding the use of each one.To be aware of the use of the Arabin pessary.
RESUMO
OBJECTIVE: Control of cervical function is poorly understood. The major structural component of the cervix is collagen and peri-partum cervical changes are largely due to the action of collagenase, either released by resident cells or derived from an influx of neutrophils. More importantly, the cell type that initiates the changes in the cervix is unknown although the resident fibroblast is a possible contender. Little is known about the state of the cervical fibroblast during pregnancy. Decidualisation of the endometrium is essential for implantation and pregnancy. In man, pre-decidual and decidual transformation of endometrial stroma occurs under the influence of progesterone. Decidualisation can also be induced in vitro in endometrial fibroblast-like stromal cells where the process is also dependent on elevated intracellular cAMP levels. STUDY DESIGN: Cultured human cervical fibroblasts were treated with progestin (medroxyprogesterone acetate) and cAMP elevating agents for 6 and 10 days. RESULTS: After 6 days they expressed and released IGFBP-1 and prolactin (PRL) and underwent morphological changes by 10 days. In addition, there was an increase in progesterone receptor and prostaglandin E type 2 receptor mRNA (but not type 4). CONCLUSION: The propensity of cervical stromal cells to decidualise suggests that these differentiated cells may be a better model with which to study the initiation of labour.
