剖腹生產可能影響之後的死產機率


  Nov. 27, 2003--根據一項發表於11月29日The Lancet期刊的研究結果顯示,剖腹生產與之後的死產有關!依據一項出院資料的分析結果顯示,曾經接受剖腹生產會增加女性因分娩期間子宮破裂而造成死產及新生兒死亡的風險達兩倍左右。
  
  英國劍橋大學Gordon C. S. Smith和同事表示,「胎盤併發症」如胎盤剝離和前置胎盤在以前接受過剖腹產手術的女性較常見,然而對於出生前死產比例的影響則未知。
  
  利用time-to-event分析,調查人員結合了1980到1998年間的蘇格蘭發病記錄及1985到1998年間的蘇格蘭死產及嬰兒死亡調查以估計第二次懷孕的出生前死產的相對危險性。
  
  研究顯示,在120,633位母親是第二次分娩的獨生子之中,17,754位過去接受剖腹手術的女性中有68位分娩前死產 (每星期每10,000位女性中約有 2.39位 ),而102,879位自然生產的女性則有244位分娩前死產(每星期每10,000位女性中約有 1.44位;P < .001 )。
  
  懷孕期為34週或以上者,會使之前接受過剖腹生產手術的不明死產風險增加一倍(hazard ratio [HR], 2.23; 95% confidence interval [CI], 1.48 - 3.36; P = .04),在調整了母親特性或第一個懷孕結果之後,並沒有降低這個風險(HR, 2.74; 95% CI, 1.74 - 4.30)。
  
  超過39週的懷孕期,每1,000位曾經接受過剖腹產女性的不明死產絕對風險為1.1,每 1,000 位自然產的女性則為0.5,曾經接受過剖腹產的女性中不明死產的過量主要說明了這項差異,研究限制包括缺乏母親體重的資料和其他不可測量的潛在干擾因子。
  
  作者指出這些結果對於計劃再次懷孕的女性在考慮剖腹產上的關係重大,剖腹產能降低自然產所造成的出生前後發病率與死亡率的風險,每1,000次分娩大約有8.3次的發生機率。
  
  作者表示,過去接受過剖腹產的二次懷孕整體死產風險的超出量低於1,000分之一,這不太可能影響初次懷孕生產方式的決定。
  
  然而,若是沒有經過明確的產學建議就勸告婦女接受剖腹產,例如為母親自己要求剖腹產,則應該討論對於未來懷孕的不明死產風險的可能影響。
  
  這些結果也與之前曾經接受過剖腹產的女性在考慮下次懷孕的生產方式有關,作者推論,目前的資料顯示在39週的懷孕期以再次的剖腹產的附加好處在於能降低不明死產的風險。
  
  在一項支持性社論中,來自澳洲維多利亞卡爾頓的母親與兒童健康研究中心的Judith M. Lumley指出這些研究發現,並指出能重新定義在產科病房照護中有關剖腹產地位的爭議本質,她並討論上述提及的風險和生產決定的關聯。
  
  她表示,未來新生兒的風險如何與了解不足的婦女骨盆損害(及可能的大小便失禁)風險是否達成平衡?何者能讓人相信而鼓勵醫師及婦女將剖腹產視為合理的選擇?是否所有曾經接受過剖腹產的婦女在38週懷孕期,甚至是34週懷孕期就該預約作再次的剖腹產手術?需要多大的試驗才能區分不同方式間的選擇?比其他地區醫院有較多剖腹出生的產科醫院應該更認真思考減少剖腹產次數的策略。不利胎兒結果的種類顯示出一項普通且安全的醫療介入會有多複雜多樣性的病理生理學的結果。
  

Cesarean Delivery Linked to Su

By Laurie Barclay, MD
Medscape Medical News

Nov. 27, 2003 — Cesarean delivery is linked to subsequent stillbirths, according to the results of a study published in the Nov. 29 issue of The Lancet. Based on an analysis of discharge data, women with one previous cesarean delivery have about twice the risk of stillbirth or neonatal death from intrapartum uterine rupture.

"Placental complications, such as abruption and placenta praevia are more common in women who have previously undergone caesarean section," write Gordon C. S. Smith, from Cambridge University in the U.K., and colleagues. "Effects on the rate of antepartum stillbirth are unknown."

Using time-to-event analyses, the investigators estimated the relative risk of antepartum stillbirth in second pregnancies by linking pregnancy discharge data from the Scottish Morbidity Record from 1980 through 1998 and the Scottish Stillbirth and Infant Death Enquiry from 1985 through 1998.

Of 120,633 singleton second births, there were 68 antepartum stillbirths in 17,754 women with previous cesarean deliveries (2.39 per 10,000 women per week) and 244 in 102,879 women with previous vaginal deliveries (1.44 per 10,000 women per week; P < .001).

Gestational age of 34 weeks or older doubled the risk of unexplained stillbirth associated with previous cesarean delivery (hazard ratio [HR], 2.23; 95% confidence interval [CI], 1.48 - 3.36; P = .04). Adjustment for maternal characteristics or outcome of the first pregnancy did not attenuate this risk (HR, 2.74; 95% CI, 1.74 - 4.30). After 39 weeks' gestation, the absolute risk of unexplained stillbirth was 1.1 per 1,000 women with previous cesarean delivery and 0.5 per 1,000 in women with previous vaginal delivery. An excess of unexplained stillbirths among women with previous cesarean deliveries primarily accounted for this difference.

Study limitations include lack of information on maternal weight and other unmeasured potential confounders.

The authors note that these results are relevant to women considering cesarean delivery who are planning further pregnancies. Cesarean delivery reduces the risk of perinatal morbidity and mortality associated with vaginal breech birth, which is about 8.3 per 1,000 births.

"The overall excess risk of stillbirth in a second pregnancy that was associated with a previous caesarean delivery was below one per 1,000, which is unlikely to influence the decision to have a caesarean section for breech presentation in a first pregnancy," the authors write. "However, if women are being counselled about caesarean birth with no clear obstetric advantage, such as caesarean section for maternal request, the possible effect on the risk of unexplained stillbirth in future pregnancies should be discussed."

These findings are also relevant for women with previous cesarean delivery who are considering mode of delivery in a subsequent pregnancy. "The current data suggest that an additional benefit of planned repeat caesarean delivery at 39 weeks' gestation may be to reduce the risk of unexplained stillbirth," the authors conclude.

The authors declare no financial conflicts of interest.

In an accompanying commentary, Judith M. Lumley, from the Centre for the Study of Mothers' and Children's Health in Carlton, Victoria, Australia, notes that these findings "could redefine the nature of the debate about the place of caesarean delivery in maternity care." She discusses the risks noted above and their implications for obstetrical decision-making.

"How will the risks [to a future fetus] be balanced against the poorly understood risks to the mother of pelvic-floor damage (and possible incontinence), which are believed to be encouraging women and obstetricians to accept caesarean birth as a reasonable choice?" she writes. "Should all women with a previous caesarean section be booked for a repeat caesarean delivery at 38 weeks or even 34 weeks? How big would trials need to be to distinguish between different management options?... Maternity hospitals where caesarean first births are commoner than in other local settings need to think more seriously about strategies for reducing the number of caesarean sections. The range of adverse fetal outcomes shows how complex and multiple the pathophysiological consequences of a common and apparently safe intervention can be."

She reports no conflict of interest.

Lancet. 2003;362:1779-1784

Reviewed by Gary D. Vogin, MD

    



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