Researchers presented a conundrum to new mothers on Monday, saying that women who want to lose the extra weight gained in pregnancy should try to get more sleep.

They found that mothers who slept five hours or less a day when their babies were six months old were three times more likely than more rested mothers to have kept on the extra weight at one year.

"We've known for some time that sleep deprivation is associated with weight gain and obesity in the general population, but this study shows that getting enough sleep -- even just two hours more -- may be as important as a healthy diet and exercise for new mothers to return to their pre-pregnancy weight," said Erica Gunderson of Kaiser Permanente, which runs hospitals and clinics in California.

Gunderson and colleagues studied 940 women taking part in a study of prenatal and postnatal health at Harvard Medical School in Boston.

The women who slept five hours or less a night when their babies were six months old were more likely to have kept on 11 pounds (5 kg) of weight one year after giving birth, they found.

Women who slept seven hours a night or more lost more weight, they reported in the American Journal of Epidemiology.

The researchers acknowledged this may pose a dilemma to new mothers, given that infants sleep so fitfully.

"With the results of this study, new mothers must be wondering, 'How can I get more sleep for both me and my baby?' Our team is working on new studies to answer this important question," said Dr. Matthew Gillman of Harvard Medical School and Harvard Pilgrim Health Care.

研究人員于本周一稱，新媽媽們如果想減掉懷孕期間增加的體重，應該多睡覺，這可要讓新媽媽們犯難了。

研究人員發現，在寶寶六個月大時，每天只睡五小時或不足五小時的媽媽在生完孩子一年后不能減掉多余體重的幾率是那些睡眠充分的媽媽的三倍。

“凱撒永久”醫療保健機構的埃里卡•甘德森說：“我們知道，對于普通人群來說，睡眠不足會導致體重增加和肥胖，而我們的這項研究表明，女性在產后保持充足的睡眠有助于她們恢復孕前體重，這與健康飲食和鍛煉身體同等重要。哪怕每天多睡兩個小時，情況就會大不一樣。” “凱撒永久”醫療保健機構在加利福尼亞開設有醫院和診所。

甘德森及其同事對940名女性進行了研究，這些女性都參加過波士頓哈佛醫學院的產前及產后健康研究。

他們發現，在寶寶六個月大時，每晚只睡五小時或不足五小時的媽媽在生完孩子一年后更難減掉體重，她們在懷孕期間增加的11磅（5公斤）多余體重沒有減掉。

而每晚睡眠時間達七小時或七小時以上的媽媽減掉的體重更多。該研究報告在《美國流行病學》期刊上發表。

研究人員承認這可能會讓新媽媽們為難，因為嬰兒的睡眠是斷斷續續的。

哈佛醫學院及哈佛朝圣保健機構的馬修•吉爾曼博士說：“新媽媽們知道這一研究結果后，一定會問，‘那怎樣才能既保證孩子的睡眠，又保證我的睡眠？’目前，我們的研究小組正在研究這一重要問題。”