Among the 49,479 women in the database, 1624 (3.3%) were screened HBsAg seropositive. There were no difference in mean maternal age, incidence of AMA, height, weight, BMI or overweight gravidae between the HBsAg seropositive and seronegative women, but the former had a slightly but significantly higher mean gestational weight gain, a slightly but significantly lower incidence of nulliparity (RR 0.963, 95% CI 0.935–0.992), and women who received tertiary education (RR 0.829, 95% CI 0.784–0.827, Table 1).
Table 1
Maternal characteristics between HBV carriers and non-carriers with singleton pregnancies delivering at/beyond 28 completed weeks of gestation
| Hepatitis B carrier | | |
| Yes (n = 1624) | No (n = 47855) | p | RR (95% CI) |
Age (years) | 29.6±4.4 | 29.7±4.3 | 0.666 | - |
≥35 years (%) | 13.2 | 13.6 | 0.653 | 0.971 (0.856–1.103) |
Height (cm) | 159.9±4.9 | 160.1±5.3 | 0.232 | - |
Weight pre-pregnant (kg) | 53.2±8.0 | 53.5±8.0 | 0.179 | - |
Weight pre-delivery (kg) | 67.8±8.4 | 67.7±8.7 | 0.584 | - |
Gestational weight gain (kg) | 14.5±4.9 | 14.3±4.9 | 0.030 | - |
Body mass index (kg/m2) | 20.8±3.0 | 20.8±2.9 | 0.585 | - |
Overweight/obese (%) | 12.6 | 12.8 | 0.846 | 0.987 (0.867–1.124) |
Nulliparity (%) | 73.1 | 76.1 | 0.009 | 0.963 (0.935–0.992) |
Previous miscarriage ≥1 (%) | 1.3 | 1.0 | 0.296 | 1.260 (0.817–1.945) |
Previous abortion ≥1 (%) | 12.9 | 12.5 | 0.574 | 1.038 (0.913–1.183) |
Previous cesarean delivery (%)* | 42.4 | 45.8 | 0.168 | 0.927 (0.829–1.036) |
Pregnancy by ART (%) | 1.2 | 0.7 | 0.045 | 1.595 (1.008–2.524) |
Tertiary education (%) | 43.3 | 52.2 | < 0.001 | 0.829 (0.784–0.827) |
*Among multiparous gravidae |
When the pregnancy outcomes were compared between the two groups, no difference in the incidence of either chronic hypertension or pre-gestational diabetes, or in pregnancy complications, could be found (Table 2). For PHD, the two groups had similar incidences whether for overall incidence of pregnancy hypertensive disorders, gestational hypertension alone, or preeclampsia alone. Similarly for PTB, no difference in overall PTB, or in early (< 34 weeks gestation) or late PTB could be demonstrated.
Table 2
Pregnancy outcome between HBV carriers and non-carriers with singleton pregnancies delivering at/beyond 28 completed weeks of gestation
| Hepatitis B carrier | | |
| Yes (n = 1624) | No (n = 47855) | p | RR (95% CI) |
Chronic hypertension (%) | 0.4 | 0.4 | 0.709 | 1.154 (0.543–2.451) |
All hypertensive pregnancy (%) | 4.2 | 4.6 | 0.442 | 0.912 (0.720–1.155) |
Gestational hypertension (%) | 1.6 | 1.9 | 0.368 | 0.835 (0.563–1.238) |
Pre-eclampsia/eclampsia (%) | 2.7 | 2.8 | 0.788 | 0.960 (0.711–1.295) |
Pre-gestational diabetes (%) | 0.6 | 0.6 | 0.881 | .951 (0.490–1.843) |
Gestational diabetes (%) | 13.9 | 15.5 | 0.073 | 0.895 (0.791–1.012) |
Placenta previa (%) | 2.2 | 2.9 | 0.126 | 0.775 (0.559–1.076) |
Placental abruption (%) | 0.8 | 0.9 | 0.802 | 0.932 (0.538–1.615) |
Preterm birth < 34 weeks (%) | 2.0 | 2.2 | 0.577 | 0.904 (0.635–1.288) |
Preterm birth 34-<37 weeks (%) | 6.3 | 5.8 | 0.437 | 1.080 (0.890–1.310) |
All preterm birth (%) | 8.1 | 7.8 | 0.706 | 1.033 (0.874–1.220) |
Postdated (≥41.4 weeks) birth (%) | 0.4 | 0.3 | 0.845 | 1.085 (0.481–2.446) |
For labor/delivery outcome, women seropositive for HBsAg had significantly lower incidence of labor induction (RR 0.827, 95% CI 0.714–0.958), but no difference in incidence of CS, PPH overall or severe PPH, or admission into the ICU (Table 3). For infant outcome, there was no difference in the mean gestational age at delivery or birthweight, incidence of LGA infants, admission into the NICU, or neonatal death, but there was a small but significantly lower incidence of SGA infants (RR 0.854, 95% CI 0.734–0.994).
Table 3
Labor / delivery and maternal and infant outcome between HBV carriers and non-carriers with singleton pregnancies delivering at/beyond 28 completed weeks of gestation
| Hepatitis B carrier | | |
| Yes (n = 1624) | No (n = 47855) | p | RR (95% CI) |
Labor induction (%) | 10.1 | 12.2 | 0.010 | 0.827 (0.714–0.958) |
Cesareran delivery (%) | 34.9 | 34.8 | 0.949 | 1.002 (0.937–1.072) |
All postpartum hemorrhage (%) | 10.7 | 10.3 | 0.667 | 1.032 (0.894–1.192) |
Postpartum hemorrhage ≥1500 ml (%) | 1.0 | 1.1 | 0.647 | 0.891 (0.543–1.462) |
Matertnal ICU admission (%) | 0.7 | 0.6 | 0.630 | 1.152 (0.648–2.046) |
Maternal death (%) | 0 (n = 0) | 0 (n = 9) | 1.000 | - |
Gestational age (weeks) | 38.9±1.6 | 38.9±1.9 | 0.956 | - |
Birthweight (g) | 3172±459 | 3158±534 | 0.254 | - |
Large-for-age (%) | 8.4 | 7.9 | 0.445 | 1.066 (0.905–1.255) |
Small-for-age (%) | 9.5 | 11.2 | 0.040 | 0.854 (0.734–0.994) |
Admit NICU (%) | 17.2 | 17.3 | 0.924 | 0.995 (0.892–1.109) |
Neonatal death (%) | 0.4 | 0.5 | 0.776 | 0.897 (0.423–1.899) |
Finally multiple logistic regression analysis was performed to examine the independent association between HBsAg seropositivity with various pregnancy outcomes (Table 4). In the first model, the confounding variables adjusted for included nulliparity status, AMA, high BMI, previous miscarriage, abortion and CS. Maternal HBsAg seropositivity was independently associated with increased spontaneous labor (aRR 1.231, 95% CI 1.044–1.451) and reduced SGA infants (aRR 0.842, 95% CI 0.712–0.997). When additional adjustment was made for the confounding factors of tertiary education and pregnancy by ART technology (model two), the associations remained the same for spontaneous labor (aRR 1.191, 95% CI 1.010–1.405) and SGA infants (aRR 0.832, 95% CI 0.703–0.984), but not for other outcomes.
Table 4
Multiple logistic regression analysis on HBV carriage on pregnancy outcome. Result expressed in P value, relative risk (95% confidence intervals). Significant results shown in bold.
Pregnancy outcome | Model One | Model Two |
Hypertensive pregnancy | 0.481, 0.914 (0.713–1.173) | 0.349, 0.888 (0.692–1.139) |
Gestational hypertension | 0.432, 0.851 (0.569–1.273) | 0.466, 0.861 (0.576–1.288) |
Pre-eclampsia | 0.800, 0.961 (0.705–1.310) | 0.554, 0.910 (0.667–1.242) |
Gestational diabetes | 0.090, 0.882 (0.762–1.020) | 0.168, 0.902 (0.780–1.044) |
Placenta previa | 0.110, 0.760 (0.543–1.064) | 0.068, 0.731 (0.522–1.023) |
Preterm birth < 34 weeks | 0.509, 0.885 (0.616–1.271) | 0.274, 0.816 (0.568–1.174) |
Preterm birth 34-<37 weeks | 0.508, 1.072 (0.872–1.319) | 0.816, 1.025 (0.833–1.261) |
Spontaneous labor | 0.014, 1.231 (1.044–1.451) | 0.038, 1.191 (1.010–1.405) |
Large-for-age infants | 0.472, 1.068 (0.893–1.277) | 0.524, 1.060 (0.886–1.268) |
Small-for-age infants | 0.046, 0.842 (0.712–0.997) | 0.032, 0.832 (0.703–0.984) |
Neonatal death | 0.723, 0.873 (0.410–1.855) | 0.564, 0.801 (0.376–1.704) |
Model one – adjusting for the effects of nulliparity status, maternal age ≥35 years, high body mass index, previous miscarriage, abortion and cesarean section |
Model two – adjusting for the above factors plus tertiary eduication, and conception by assisted reproduction rtechnology |