When one of these women gave birth to a child without knowing which sailor had fathered it, the paternity was logged as  gun,  perhaps alluding to the midship gun, which was often located near the makeshift maternity room.
( ( When ( ( one ( of ( these women ) ) ) ( ( ( gave birth ) ( to ( a child ) ) ) ( without ( knowing ( which ( sailor ( had ( fathered it ) ) ) ) ) ) ) ) ) ( , ( ( the paternity ) ( ( was ( ( ( logged ( as gun ) ) , ) ( perhaps ( alluding ( to ( ( ( the ( midship gun ) ) , ) ( which ( ( was often ) ( located ( near ( the ( makeshift ( maternity room ) ) ) ) ) ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (NP (CD one)) (PP (IN of) (NP (DT these) (NNS women)))) (VP (VBD gave) (NP (NN birth)) (PP (TO to) (NP (DT a) (NN child))) (PP (IN without) (S (VP (VBG knowing) (SBAR (WHNP (WDT which)) (S (NP (NN sailor)) (VP (VBD had) (VP (VBN fathered) (NP (PRP it)))))))))))) (, ,) (NP (DT the) (NN paternity)) (VP (VBD was) (VP (VBN logged) (PP (IN as) (NP (NN gun))) (, ,) (S (ADVP (RB perhaps)) (VP (VBG alluding) (PP (TO to) (NP (NP (DT the) (NN midship) (NN gun)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBD was) (ADVP (RB often)) (VP (VBN located) (PP (IN near) (NP (DT the) (JJ makeshift) (NN maternity) (NN room))))))))))))) (. .)))
Gun is a term used in hospitals frequently. 
( Gun ( ( is ( ( a term ) ( ( used ( in hospitals ) ) frequently ) ) ) . ) )
(ROOT (S (NP (NNP Gun)) (VP (VBZ is) (NP (NP (DT a) (NN term)) (VP (VBN used) (PP (IN in) (NP (NNS hospitals))) (ADVP (RB frequently))))) (. .)))