A new British research found a very different pattern amongst races and the possibility of complications during labor, whether before, during or after giving birth.

South Asian women are at a higher risk of delivering babies prone to perinatal mortality (death before, during or shortly after birth) compared to black or white women.

The World Health Organization states as post-term pregnancy when it passes of 41 weeks from the first day of the last menstrual period.

Post-term pregnancy is connected to increased perinatal mortality, that's why often the physicians induce the labor at 41 weeks to avoid risks.

But the new research points out that the average length of gestation differs between racial groups. This period is shorter in Asian and black women, thus complications may occur before the 41 weeks in these categories.

Researchers from London and Bristol tested this theory by studying whether the risks of post-term birth complications increased earlier during pregnancy in South Asian and black women compared with white women. The investigators had at their disposal over 197,000 white, South Asian and black women who were expecting their first child and who delivered a single baby weighing at least 500 grams at 24 to 43 weeks.

They discovered that the perinatal mortality varied significantly linked to the racial group. The mortality level among black women was lower before 32 weeks than among white women, but after this period, the black women were more prone to delivering still babies. "Perinatal mortality was highest among south Asian women at all gestational ages and increased the fastest at term. The most important risk factor for antepartum stillbirth in white women was placental abruption, but the most important factor in south Asian and black women was birth weight below 2,000 grams", noted the researchers.

The research discovered that there are genetic variations in gestational length amongst races and higher fetal surveillance and growth monitoring from 40, rather than 41 weeks' gestation is required for South Asian and black women. In south Asian women, the mortality was found higher for every factor, like congenital abnormality, fever, maternal body mass index and abruption to the placenta.