paa Ma 2014.

Methods	Controlled clinical trial. The effect of pandemic influenza vaccine administration during pregnancy was assessed by comparing the occurrence and the characteristics of pregnancy outcomes and clinical course between vaccinated and non‐vaccinated women and assessing the effectiveness of vaccine administration in preventing ILI.
Participants	Healthy pregnant women between the age of 18 and 35 (n = 226) recruited in 4 adjacent villages of Xiangshui, Jiangsu Province, China. The pregnancies ranged from 5 weeks’ to 32 weeks’ gestation; 122 women received the H1N1 vaccine, whereas 104 formed the control group and did not receive any vaccination. Pregnant women in the control group had to reside in the same or adjacent village/community and have an age difference of < 3 years compared to the women in the vaccinated group, a gestational age of < 3 weeks, and the same numbers of pregnancies as those in the vaccinated group.
Interventions	Split‐virion nonadjuvanted influenza A(H1N1) vaccine (lot 200909008; Shanghai Institute of Biological Products). Each dose contained 15 µg of H1N1 antigen.
Outcomes	Pregnancy outcomes were recorded by the maternity and child healthcare organisations or midwifery agencies according to routine prenatal and delivery services in the pregnant women’s health records (filling out of a unified form on complications during pregnancy and pregnancy outcomes): Spontaneous abortion Artificial abortion Postnatal death Premature birth Prolonged pregnancy Low birth weight Delivery mode (eutocia or Caesarean delivery) Birth weight (< 3500 g or > 3500 g) Apgar score at 1 min (7 to 8 or > 9) Effectiveness outcomes Influenza‐like illness was defined according to WHO guidelines, which include documented fever (at least 38.0 °C) and cough or sore throat. Participants were asked to contact the local vaccination site or the Xiangshui County Center for Disease Control and Prevention once influenza‐like symptoms appeared.
Notes	Funding source ‐ government This study has been registered at ClinicalTrials.gov under registration no. NCT01842997.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not described, only stated that participants were “divided” into 2 groups.
Allocation concealment (selection bias)	High risk	Absent
Blinding (performance bias and detection bias) All outcomes	High risk	Not blinded
Incomplete outcome data (attrition bias) All outcomes	Low risk	No loss to follow‐up
Summary assessment	High risk	High risk of bias