Possible Roles of Proinflammatory and Chemoattractive Cytokines Produced by Human Fetal Membrane Cells in the Pathology of Adverse Pregnancy Outcomes Associated with Influenza Virus Infection

Table 3

Risk of preterm birth and abortion among 181 women who needed hospitalization for A(H1N1)pdm09 virus infection.

Characteristics	Japan^a	Study	Pneumonitis
			Absent	Present
No. of pregnant women	1,091,156	181	164	17
abortion at <22 weeks	NA	3/181 (1.7%)	2/164 (1.2%)	1/17 (5.9%)
Preterm birth
22–31 weeks	7,876/1,091,156 (0.7%)	5/178 (3.8%)^†	5/162 (3.1%)^†	0/16 (0.0%)
32–36 weeks	54,932/1,091,156 (5.0%)	21/178 (11.8%)^†	16/162 (9.8%)^†	5/16 (29.4%)^†‡
Term birth	1,028,348/1,091,156 (94.2%)	152/178 (85.4%)^†	141/162 (86.0%)^†	11/16 (68.8%)^†

NA, national statistics concerning spontaneous abortion at <22 weeks of gestation is not available.
^†P < 0.01 versus Japan (national statistics); ^‡P < 0.05 versus women group without pneumonitis.
^aNational data of Japan in 2008 were presented as a comparison group.
This table is reproduced from Nakai et al. [39] with minor modifications.