THURSDAY, Oct. 9, 2014 (HealthDay News) -- When it comes to pain relief during labor and delivery, mom probably knows best, new research suggests（新近研究表明，何时应该给正在分娩的准妈妈们实施镇痛？，如给予硬膜外麻醉，孕妇的判断或选择往往较医生们更准确。据此，本研究建议产科专家或医生，在是否给予分娩女性镇痛处理这个问题上，尊重正在分娩时的准妈妈之选择）.

Doctors tend to be cautious about when to give the pain-relieving local anesthetic known as an epidural during labor. But, a new study says the best time to give an epidural is likely when a woman asks for it.

Researchers reviewed nine studies that included more than 15,000 first-time mothers randomly assigned to receive an epidural either early or late during childbirth. Those given early epidurals were less than 4 to 5 centimeters dilated, while those given late epidurals were 4 to 5 centimeters or more dilated.

In a normal vaginal delivery, the baby is delivered after the woman's cervix is dilated to 10 centimeters, according to the American Pregnancy Association.

Compared to women who had late epidurals, those who had early epidurals were no more likely to require a cesarean delivery, to need assisted birth involving forceps or suction, or to spend more time in the pushing stage of labor, the investigators found.

The effect of early epidural on the length of time to reach full cervical dilation was unclear, according to the findings published Oct. 8 in The Cochrane Library.

"The right time to give the epidural is when the woman requests pain relief," said lead researcher Dr. Ban Leong Sng, deputy head and senior consultant in the department of women's anesthesia at KK Women's and Children's Hospital in Singapore.

"If they request an epidural early during their labor, the evidence we have does not provide a compelling reason why this should be refused," Sng said in a Cochrane news release.

Previous studies have suggested that the timing of an epidural can affect the length of labor and the risk of cesarean section.

SOURCE: The Cochrane Library, news release, Oct. 8, 2014