Pregnant women who smoke in the early stages of pregnancy were found to have placental weights 182g heavier compared to non-smoking women. Furthermore, this has been linked to a decrease in the average birth weight of newborns.
According to a study published on April 8 in the international academic journal BMC Pregnancy and Childbirth, a research team led by Annika Jaitner of the University of Exeter in the UK revealed this finding. The team conducted a study on 4,600 pairs of mothers and their children, investigating factors such as whether the mother smoked during pregnancy, the amount of smoking, placental weight, and the weight of the child after birth.
The placenta is an organ that connects the fetus to the mother’s uterus, supplying oxygen and nutrients from the mother to the fetus. It also manages the fetus’s waste disposal.
The study found that mothers who smoked more than one cigarette a day in the early stages of pregnancy had placentas that weighed 182g heavier than those of non-smoking mothers before giving birth. The correlation became stronger if the mother continued to smoke towards the end of pregnancy (36 weeks).
Further research indicated that the heavier the placental weight, the lower the fetus’s birth weight tended to be.
The research team explained that this is because smoking converts some of the oxygen in the blood into carbon monoxide. Therefore, when a mother smokes, not only does the oxygen level in her blood decrease but so does the oxygen level in the fetus’s blood. This results in poor blood circulation in the umbilical cord and placenta, leading to inadequate nutrients for the fetus.
The researchers stated, “The placenta can grow larger than the birth weight to meet the oxygen needs of the fetus and restore the oxygen binding sites. If the placenta is thicker, it can interfere with the delivery of oxygen and nutrients, leading to more frequent developmental delays in the fetus.”
This study was published in the April issue of the international academic journal BMC Pregnancy and Childbirth.