Study also points to early pregnancies when women may be underweight

The “Asian enigma” of why Indian children end up being shorter and smaller than African children appears to have been resolved — Indian mothers are underweight prior to conception (BMI less than 18.5) and gain less weight during pregnancy. Hence, there is a deficit in maternal nutrition during pregnancy, and this deficit tends to affect the baby even after birth.

According to a paper published on Tuesday in the journal Proceedings of the National Academy of Sciences, 42.2 per cent of pre-pregnant Indian women are underweight compared with only 16.5 per cent in the case of sub-Saharan African mothers.

Worse, pre-pregnancy underweight in India is 7 percentage points higher than that of average women. “The most important reason why pre-pregnant women in India are more likely to be underweight than the average women is age,” Diane Coffey, a researcher at Princeton University and the author of the paper said in an email to this Correspondent. “Indian women have children very soon after marriage, in a narrow age range between about 18 and 25. This is also the time in their lives that they are most likely to be underweight.”

Sub-Saharan African women in their early 20s are 20 percentage points less likely to be underweight than Indian women of the same age group.

Besides age, those belonging to the socioeconomically disadvantaged stratum are more likely to be underweight prior to conception. But the problem is not confined to the socioeconomically disadvantaged population alone.

According to Ms. Coffey, there are three reasons why pre-pregnant women in India end up being underweight. First, even in well-to-do families, young women tend to have low social rank. As a result, they have less than adequate food. Second, besides food intake, diseases such as diarrhoea due to wide prevalence of open defecation play a critical role in determining the weight of mothers before pregnancy. Even wealthy women who themselves use toilets are affected as long as open defecation is practised in the neighbourhood.

“[Researchers] have found that Muslim children are more likely to survive infancy because fewer people in Muslim neighbourhoods defecate in the open,” she said.

Finally, very high levels of air pollution in India play a critical role in reducing life expectancy for about half of the Indian population. “Air pollution also contributes to low birth weight babies, Ms. Coffey noted. “There is convincing research that mothers who breathe polluted air during pregnancy do not pass on as many nutrients and energy to their infants as mothers who are breathing clean air, so the babies are born smaller.”

Gaining weight during pregnancy

Pre-pregnant mothers who are underweight in India do not compensate it during pregnancy by gaining “adequate” weight. At about 7 kg for a full-term pregnancy, the weight gain during pregnancy is the same for both the populations despite their different starting body weights. As a result, even after gaining weight during pregnancy, Indian women end their pregnancy weighing less than even their counterparts’ weight at the beginning of pregnancy. At no point during pregnancy do Indian women match the weight of sub-Saharan women.

“To my knowledge, India has no national guidelines for healthy weight gain during pregnancy. Countries that do have guidelines base them on large studies of how pre-pregnancy body mass and weight gain during pregnancy predict infant survival and infant health,” she said.

The recommended weight gain during pregnancy for underweight women in the U.S. is between 12.5 kg and 18 kg. “In situations where there is high quality health care at delivery, this recommendation probably applies to Indian women as well. However, I certainly think that it would be great to have more large-scale studies of pre-pregnancy weight and weight gain during pregnancy in India, and for the Indian government to develop its own guidelines,” Ms. Coffey noted.

It is difficult to compensate for poor nutrition during pregnancy by giving children more and better food after birth. After all, children are required to be exclusively breastfed for the first six months. During this period, the baby comes to depend on its mothers’ “nutritional stores.”

Weight gain during pregnancy thus serves twin purposes. First, it is useful for the growth of the baby before birth. Second, it prepares the woman's body to have enough fat stores to produce lots of high quality breast milk. “Stunting is typically thought to take place in a child’s “first thousand days” between conception and two years of age. For half of this first 1,000 days, a child relies totally on the mother for nutrition,” Ms. Coffey said.

Higher prevalence of low birth weight babies in India is also linked to mother’s low pre-pregnancy weight and less weight gain during pregnancy.