Background
Chronic maternal hypertension (CMH) is associated with adverse maternal and perinatal outcomes. However, existing literature examining this association has significant heterogeneity and has limited adjustment for baseline maternal characteristics. We aimed to determine the risk of adverse maternal and perinatal outcomes in a local population of women with CMH after adjustment for recognised independent risk factors for adverse pregnancy outcomes.
Methods
Methods 230 singleton pregnancies in 186 women with CMH were identified from a retrospective database of 43,910 deliveries (2008-2018) from two maternity centres in Melbourne, Australia. In a case-control design these were matched for era, plurality and parity in a ratio of 1:4. Associations between CMH and pregnancy outcomes were evaluated after adjustment for recognised risk factors including: site, age, body mass index (BMI), smoking, diabetes, renal disease, ethnicity, gestation at first antenatal visit, and previous preeclampsia. Associations were evaluated by multiple logistic regression analysis, significance p<0.05. An additional model included further adjustment for preeclampsia and GDM.
Results
Pregnancy outcomes significantly associated with CMH after adjustment for recognised risk factors included: any preeclampsia, severe preeclampsia, induction of labour, Caesarean section (CS) without labour, maternal ICU admission, preterm delivery, iatrogenic preterm delivery, small gestational age (SGA), and neonatal admission to SCU/NICU. There was a significant negative association with normal vaginal delivery. There was no association with postpartum haemorrhage (PPH), emergency CS or stillbirth (Table 1, Model 1). Adjusting further for preeclampsia and GDM, maternal admission to ICU was no longer significant, however iatrogenic preterm delivery, induction, SGA and neonatal SCN/NICU admission remained significant (Model 2).
Table 1.
|
|
Normotensive Controls n = 920 |
Chronic Maternal Hypertension n = 230 |
Adjusted OR (Model 1) |
Adjusted OR (Model 2) |
|
GDM |
100 (12.19%) |
48 (26.3%) |
ns |
- |
|
All Preeclampsia |
13 (1.14%) |
30 (13.04%) |
10.29 (4.68-22.63) |
- |
|
Severe Preeclampsia |
3 (0.33%) |
14 (6.09%) |
23.5 (5.71-96.7) |
- |
|
Estimated Primary Blood Loss (mL) |
417 ± 229.88 |
493.23 ± 279.15 |
- |
- |
|
PPH |
159 (17.34%) |
49 (21.49%) |
ns |
- |
|
Severe PPH |
58 (6.32%) |
25 (10.96%) |
ns |
- |
|
Blood Transfusion |
17 (1.85%) |
8 (3.48%) |
ns |
- |
|
Induction of Labour |
218 (23.7%) |
106 (46.09%) |
4.31 (2.72-6.78) |
3.76 (2.36-5.99) |
|
Normal Vaginal Delivery |
541 (58.8%) |
81 (35.22%) |
0.42 (0.29-0.61) |
0.46 (0.31-0.66) |
|
Assisted Vaginal Delivery |
105 (11.4%) |
27 (11.74%) |
ns |
- |
|
CS in Labour |
110 (11.96%) |
30 (13.04%) |
ns |
- |
|
CS without Labour |
162 (17.61%) |
92 (40%) |
2.28 (1.55-3.34) |
1.96 (1.32-2.92) |
|
Emergency CS |
118 (12.82%) |
54 (23.47%) |
ns |
- |
|
Maternal ICU Admission |
2 (0.22%) |
9 (3.91%) |
15.04 (2.58-87.46) |
ns |
|
Gestation at Delivery (weeks) |
39.4 ± 1.46 |
38.3 ± 2.23 |
- |
- |
|
Preterm Delivery |
45 (4.89%) |
29 (12.61%) |
3.77 (2.04-6.97) |
2.47 (1.25-4.84) |
|
Iatrogenic Preterm Delivery |
26 (2.83%) |
26 (11.3%) |
7.59 (3.72-15.38) |
4.73 (2.17-10.29) |
|
Spontaneous Preterm Delivery |
19 (2.07%) |
2 (0.87%) |
ns |
- |
|
Birthweight (g) |
3442 ± 517 |
3220 ± 676 |
- |
- |
|
SGA |
76 (8.27%) |
33 (14.35%) |
2.88 (1.67-4.94) |
2.48 (1.41-4.35) |
|
Baby Sex (male) |
468 (52.83%) |
114 (49.57%) |
ns |
- |
|
Neonatal SCN/NICU Admission |
98 (10.68%) |
49 (21.40%) |
2.01 (1.24-3.24) |
1.67 (1.02-2.76) |
|
Stillbirth |
3 (0.33%) |
1 (0.43%) |
ns |
- |
Table 1. Frequency, mean±SD, adjusted OR. Model 1: adjusted for recognised risk factors. Model 2: adjusted for recognised risk factors + preeclampsia/GDM. ns=not significant.
Conclusion
Multiple adverse pregnancy outcomes were associated with CMH after adjustment for recognised risk factors. Some adverse outcomes (induction, CS, preterm delivery, SGA and SCN/NICU admission) were independent of superimposed preeclampsia and GDM. This suggests pregnancy morbidity in CMH may be only partly attributable to preeclampsia and/or GDM. These findings confirm the need for pre-pregnancy counselling, early pregnancy risk stratification and fetal surveillance in these women.