Pre-Conception Paternal Smoking Not Associated with Adverse Neonatal Outcomes

Shi Wu Wen, PhD

A new investigation into pre-conception paternal smoking found no associations with birth weight or adverse neonatal outcomes at delivery.

Previous studies maintained a focus on paternal smoking during pregnancy as an indicator of passive maternal exposure as opposed to prior to conception. However, there is limited data on the potential effect of pre-conception paternal smoking.

In the current study, investigators led by Shi Wu Wen, PhD, School of Epidemiology and Public Health at the University of Ottawa, evaluated the association of paternal smoking with neonatal outcomes.

The Methods

For the prospective preconception observational cohort study, investigators recruited newly married couples intending to conceive a child in Liuyang, China.

Between February 1, 2009, and November 4, 2015, all participating couples underwent baseline (pre-gravid) assessments and were monitored throughout the pregnancy.

Association of paternal smoking with birth weight and categorical neonatal outcomes were assessed by multiple linear regression and logistic regression analyses, respectively. For the study, a P < .05 was considered significant.

Wen and colleagues used t tests to evaluate the P values for the multiple linear regression analyses and χ2 tests to calculate P values for multiple logistic regression analyses. All tests that were performed were 2-sided, and all analyses were performed using the Statistical Analysis System version 9.4 (SAS Institute).

Statistical analyses were then performed between January 2021 and August 2021.

The Findings

A total of 1174 couples who underwent baseline assessment were enrolled in the study, at a median of 23.3 (IQR, 5.6-65.6) weeks before a singleton pregnancy. The mean age of the sample was 24 (3) years for women and 26 (3.5) years for men.

Throughout the pre-conception assessment, 538 male partners (45.8%) had reported currently smoking, which was in contrast to only 5 women (0.4%) smoking.

Baseline characteristics and delivery outcomes were stratified into 3 distinct groups based on the degree of paternal smoking before conception.

A total of 635 couples (54.2%) answered that they had smoked no cigarettes before the conception of their child, while 343 (29.2%) reported smoking 1 to 10 cigarettes a day. Only 195 couples (16.6%) reported having smoked more than 10 cigarettes per day.

Despite the differences in smoking habits, the birth weight and length of gestation did not differ between the 3 groups.

Investigators observed positive independent factors associated with birth weight during the multiple linear regression analysis, including maternal baseline body mass index (BMI), (regression coefficient, 39.2; 95% CI, 27.5 to 50.9; P < .001), paternal baseline BMI (regression coefficient, 17.0; 95% CI, 7.7 to 26.3; P = .001), maternal age (regression coefficient, 14.4; 95% CI, 2.7 to 26.1; P = .02), length of gestation (regression coefficient, 128.7; 95% CI, 108.4 to 149.0; P < .001), gestational weight gain (regression coefficient, 16.5; 95% CI, 12.3 to 20.8; P < .0001), and male neonate (regression coefficient, 89.1; 95% CI, 36.2 to 142.1; P = .001).

Preeclampsia was associated with lower birth weight (regression coefficient, −214.0; 95% CI, −422.9 to −5.1; P = .04), though either maternal or paternal smoking were associated with lower birth weight.

Preconception paternal smoking was not associated with birth weight (P = 37). Likewise, investigators observed no significant interaction between paternal BMI and smoking status.

Despite this new data, investigators noted they could not determine if the influence of pre-conception paternal smoking would show at later stages in the children’s lives.

“These findings cannot rule out the possibility that paternal origins of health and disease (POHaD) programming effects of preconception paternal smoking may yet emerge later in life.”

The study, "Analysis of Preconception Paternal Smoking and Neonatal Outcomes," was published online in JAMA Open Network.