The best replacement for membranes is breaking water.

The best alternatives to membranes are rated as following:
★★★★★  breaking water
★★★  mucous membranes
★★★  stretching cervix
★★★  pvc membranes
★★  mucus membranes
★★  water breaking
★  rupturing
★  cell walls
★  mucus plug
★  premature rupture of membranes
  animal cell membranes
  nitrocellulose
  polyamide membranes

Your alternative for membranes is not listed? Suggest!
Speaking about membranes, one probably shouldn't forget about meconium.

Other search terms related to membranes and their ratings are:
★★★★★ meconium
★★★ cerclage
★ visceral and parietal layers
★ passive transport across membranes
You have in mind a companion for membranes and it is not yet here? Propose!



Google Trends

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membranes
breaking water
mucous membranes