Fig 1.
PubMed and Web of Science results and reference lists of the papers produced a total of 880 unique hits. Finally, 62 original research papers covering eight types of cancer, and 12 of their subtypes, were available for the meta-analyses (Tables A-C in S1 File). NS: nervous system; c.: cancer.
Fig 2.
Cancer (sub)types which were analyzed according to exposure time window and exposure amount.
Sensitivity analyses were conducted for nine study characteristics using studies reporting “any” smoking “during pregnancy”. Exposure amount is given in cigarettes per day (CPD). PNET = primitive neuroectodermal tumor; ALL = acute lymphoblastic leukemia; AML = acute myeloblastic leukemia.
Table 1.
Categories in subgroup analyses.
Fig 3.
Planned subgroup analyses and number of identified articles for each analysis.
Each row corresponds to one cancer (sub)type as listed in Fig 2. For column definition see Table 1.
Fig 4.
Pooled estimates of meta-analyses for eight studied cancer types.
Lymphoma and brain cancers were associated with smoking during pregnancy at 95% confidence level. Random effects model was applied for leukemia only (see Tables A-K in S1 File for additional information by cancer type).
Fig 5.
Meta-analyses based on 62 original research articles for eight cancer types and any smoking during pregnancy (yes vs no).
The final model selected according to heterogeneity analyses is indicated in blue. CI = Confidence Interval.