Incidence of first-degree perineal laceration
Eleven trials involving 3618 women were included in this outcome, 3581
women contributed data. The result of meta-analysis indicated that women
in lubricant group had no statistically difference in the incidence of
first-degree perineal laceration when compared with those in standard
care group (RR 1.18, 95%CI 0.92 to 1.52; I2=87%;
very low certainty due to serious risk of bias, serious inconsistency
and serious imprecision) (Table 1, Figure S11).
Subgroup analyses showed that there was significant subgroup effect
between parity groups (P interaction<0.001) (Figure 12), but not between lubricants type groups
and between overall risk of bias (Pinteraction=0.66 and Pinteraction=0.58, respectively) (Figure S13, Figure
S14). The heterogeneity of multiparous women groups, obstetric gel
groups and high risk of bias groups was significantly reduced after
subgroup analysis (I2=0%, I2=48%
and I2=20%, respectively), while significant
heterogeneity remained within nulliparous women groups, liquid wax
groups and low high risk of bias groups (I2=82%,
I2=92% and I2=90%, respectively).
This heterogeneity might partially result from studies of nulliparous
women, liquid wax and low risk of bias (Figure S13, Figure S14).
The result analyzed based on parity indicated that both multiparous and
nulliparous women in lubricant group had statistically difference in the
incidence of first-degree perineal trauma when compared with those in
standard care group. Multiparous women had a lower incidence of
first-degree perineal trauma (RR 0.69, 95%CI 0.59 to 0.80;
I2=0%) (Figure S12), while nulliparous women had a
higher incidence of first-degree perineal trauma (RR 1.38, 95%CI 1.03
to 1.86; I2=82%) (Figure S12), which might be
associated with decreasing for incidence of second-degree perineal
laceration and the incidence of first-degree perineal trauma was
increasing relatively. Therefore, it was uncertain whether lubricant
increased or reduced the incidence of first-degree perineal trauma for
nulliparous women.