Secular increase in placental weight in Saudi Arabia

Ramadan is an annual period of day-time fasting during which people in Saudi Arabia, including pregnant women, change their diets and physical activity. We recently reported that among babies who were in the second or third trimester of gestation during Ramadan placental growth slowed. We also found that, over the four years of the study, placental weight increased by 29 g per year. We have now extended our data collection in order to examine this trend in more detail.

We studied the birth records of 17 660 singletons born in King Saud Hospital, Unizah, Saudi Arabia, over a ten year period. The records included birth weight, placental weight and gestational age.

During the first six years of the study period mean placental weight rose by more than 100 g while mean birth weight was unchanged. This secular increase in placental weight was accompanied by a change in the placenta's response to Ramadan. During the first half of the study period babies who were in their second or third trimester of gestation during Ramadan had reduced placental weight (475 g and 476 g compared with 484 g, p < 0.001 for both). During the second half of the study period babies who were in their first trimester of gestation during Ramadan had reduced placental weight (533 g compared with 539 g, p = 0.03).

We suggest that the secular increase in placental weight reflects changes in maternal body composition. These have altered placental responses to the dietary changes during Ramadan. The biological processes underlying these responses are not known.