Hypertension, preterm birth, caesarean delivery tied to low birthweight

A recent Japan study identifies a variety of modifiable and nonmodifiable risk factors for low birthweight (LBW), suggesting that this population of infants is highly heterogenous.

“[I]t may be appropriate to consider a heterogeneous rather than a simple classification of LBW and to evaluate future health risks based on contributing factors,” the researchers said.

A retrospective review of 4,224 infants was conducted, among whom the incidence of LBW was 24 percent (n=1,028). A total of 797 singleton babies were born with LBW, most (65 percent; n=518) of which were born preterm.

Logistic regression analysis showed that birth at 37 gestational weeks was a strong risk factor for LBW, increasing its likelihood by almost four times (odds ratio [OR], 3.89, 95 percent confidence interval [CI], 2.91–5.20; p<0.001).

Hypertensive disorder of pregnancy likewise had a strong impact on the odds of LBW (OR, 4.51, 95 percent CI, 2.63–7.72; p<0.0001), as did having neonatal congenital abnormalities (OR, 3.24, 95 percent CI, 2.02–5.20; p<0.0001).

Factors related to pregnancy, such as being underweight (OR, 1.42, 95 percent CI, 1.04–1.93; p=0.026) and having inadequate weight gain (OR, 2.46, 95 percent CI, 1.82–3.33; p<0.0001), also increased the likelihood of LBW. Anaemia during pregnancy had a similar effect (OR, 1.81, 95 percent CI, 1.08–3.04; p=0.024).

Infants who were born female (OR, 1.66, 95 percent CI, 0.1.28–2.17; p=0.0002) or delivered via caesarean section (OR, 1.42, 95 percent CI, 1.05–1.91; p=0.024) were also at a higher risk of LBW. In contrast, conception through in vitro fertilization–embryo transfer seemed to be significantly protective (OR, 0.64, 95 percent CI, 0.46–0.89; p=0.0075).