Pregnant women who sleep on their backs give birth to lighter babies

Researchers from the Uni­ver­si­ty of Auck­land found that sleep­ing on your back dur­ing preg­nan­cy results in a baby with slight­ly less body weight than if the moth­er pre­ferred to sleep in a dif­fer­ent body posi­tion.

The study involved 1760 preg­nant women who are at least 28 weeks preg­nant. Sci­en­tists observed them until the moment of birth.

Of these, 57 (3.2%) report­ed that they slept on their back dur­ing the last 1–4 weeks before giv­ing birth. The aver­age weight of chil­dren born to them was 3.41 kg, while the aver­age weight of babies born to women who slept on their side was slight­ly high­er — 3.55 kg.

Although in both cas­es the weight of the chil­dren was with­in the nor­mal range, nev­er­the­less, sci­en­tists indi­cate that there is a dif­fer­ence, and it is sta­tis­ti­cal­ly sig­nif­i­cant. This may be because sleep­ing on your back dur­ing the third trimester of preg­nan­cy puts pres­sure on the supe­ri­or vena cava, which returns blood from the head to the heart, and on the aor­ta, which car­ries blood to the rest of the body. Thus, the vol­ume of blood eject­ed by the wom­an’s heart decreas­es, which caus­es a decrease in blood flow to the uterus and there­by lim­its the growth of the baby.

It has also been pre­vi­ous­ly shown that there is an asso­ci­a­tion between an increased risk of still­birth and sleep­ing on your back. The increase in risks in this case is also very insignif­i­cant, but it exists. There­fore, many obste­tri­cian-gyne­col­o­gists rec­om­mend that expec­tant moth­ers sleep on their side at the end of preg­nan­cy.