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Western Diets High In N-6 Polyunsturates (PUFAs) May Increase The Risk Of Premature Birth
Elmes, M; Poore, K; Newman, J; Cheng, Z; Abayasekara, R; Hanson, M; Wathes, C
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Journal of the Society for Gynecologic Investigation
Objectives: The aim of the study was to determine the effects of a high n-6 PUFA diet as seen in western countries on prostaglandin production and the timing of dexamethasone (DEX) induced labour in late gestational ewes. Methods: Pregnant Welsh mountain ewes of 100 days gestational age (dGA, term delivery 145 dGA) were fed a control (n=6) or isoenergetic SoyPreme (rumen protected form of soya, high in the n-6 PUFA linoleic acid n=10) diet. At 131 dGA ewes and fetuses were surgically instrumented under general anaesthesia (750 mg sodium thiopentone i.v. then 2% halothane in 02) with vascular catheters and myometrial electrodes. Electromyographic (EMG) activity was monitored continuously after surgery and after 7 days postoperative recovery blood was sampled regularly for maternal prostaglandin F metabolite (PGFM) and fetal PGFM and PGE2. Labour induction was initiated on d139 by continuous infusion of DEX (1 mg/day i.v) to the fetus. When EMG burst activity reached 2 times the basal level for 2 consecutive 2h periods, ewes were judged to be in established labour and were euthanised. Data are mean and plusmn;SEM. Results: Four n-6 fed ewes initiated labour early between 132-138 dGA (before the DEX infusion) compared with only 1 control ewe. This was associated with a premature rise in both fetal and maternal PGFM. In the remaining animals, EMG activity in ewes fed the high n-6 diet increased significantly earlier from baseline levels compared to control fed ewes (n-6 (n=6) 26h post DEX infusion vs. control (n=5) 30h, P and lt;0.05). Ewes on the high n-6 diet also entered established labour (twice basal EMG activity) significantly earlier after DEX infusion than control ewes (n-6, 35 and plusmn;2.8 h vs. control, 42 and plusmn; 1.1h , P and lt; 0.05). Prior to labour induction, PG levels were approximately doubled in n-6 fed compared to control fed ewes (maternal PGFM: control 0.25 and plusmn; 0.01 ng/ml, n-6 0.43 and plusmn; 0.02, P and lt;0.001; fetal PGFM: control 0.46 and plusmn; 0.03 ng/ml, n-6 0.82 and plusmn; 0.04, P and lt;0.001; fetal PGE2: control 46 and plusmn;20 pg/ml, n-6 86 and plusmn;4, P and lt; 0.05). Fetal PGE2 increased earlier following DEX and maternal PGFM values were higher in established labour in n-6 fed ewes compared with controls (control 1.8 and plusmn;0.09 ng/ml, n-6 2.3 and plusmn;0.09, P and lt;0.02). Conclusions: A diet high in n-6 PUFAs caused a substantial increase in the concentration of maternal and fetal prostaglandins in late pregnancy. Following DEX induction, an earlier increase in PGs in n-6 fed ewes was associated with an earlier onset of established labour. Increased levels of PGs at this stage in pregnancy may thus increase the sensitivity of the signaling events that cause premature labour.
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