Follow up
All the participated women were followed up by trained local community
health worker by telephone every two months to determine whether they
had conceived successfully. Local health worker interviewed the women
face to face or by telephone within three months after conception,
documenting their last menstrual period, active smoking, alcohol
consumption, and husband smoking during the early stage of the
pregnancy. Women were also interviewed face to face or by telephone
within six weeks of delivery to collect information on the hospital
where delivery took place. Local community health workers then collected
data from the medical records at the reference hospital regarding
pregnancy outcomes, including gestational age (weeks), birth weight
(grams), obstetrical outcomes (caesarean delivery, shoulder dystocia or
birth injury), neonatal information (singleton or multiple births and
sex) and stillbirth (only collected from 46 counties in 13 cities).
All of these baseline data and fellow up data were transferred to
Guangdong Institute of Family Planning Science and Technology where they
were cleaned, complied and de-identified. The endpoint of this study was
to observe the pregnancy outcomes of the participated mothers and the
study was terminated on 31st December 2017.