Objective
The objective of the study was to estimate the maternal and neonatal morbidities associated with obstructive sleep apnea (OSA) in pregnancy.
Study Design
Women delivering between 2000–2008 with confirmed OSA in an academic center were included. Normal-weight and obese controls were randomly selected at a 2:1 ratio. Maternal and neonatal morbidities were compared between the groups. Multivariate analyses were performed to evaluate maternal morbidity and preterm birth (PTB).
Results
The analysis included 57 pregnancies complicated by OSA. Compared with normal-weight (n = 114) controls, OSA patients had more preeclampsia (PET) (19.3% vs 7.0%; P = .02) and PTB (29.8% vs 12.3%; P = .007). Controlling for comorbid conditions, OSA was associated with an increased risk of PTB (odds ratio [OR], 2.6; 95% confidence interval [CI], 1.02–6.6), mostly secondary to PET (63%). Cesarean delivery (OR, 8.1; 95% CI, 2.9–22.1) and OSA were associated with maternal morbidity (OR, 4.6; 95% CI, 1.5–13.7).
Conclusion
Pregnancies complicated by OSA are at increased risk for preeclampsia, medical complications, and indicated PTB.
Obstructive sleep apnea (OSA) is a condition marked by recurrent upper-airway obstruction, hypoventilation, and intermittent nocturnal hypoxia. Long-term complications associated with OSA include cardiovascular and noncardiovascular morbidities and mortality. The prevalence of OSA among women is estimated to be 2–5%, but it remains underdiagnosed.
Obesity is the major risk factor for the development of OSA. The Centers for Disease Control and Prevention estimates that 30% of reproductive-age women have a body mass index (BMI) of 30 kg/m 2 or greater and are considered to be obese. We and others have reported obesity to commonly complicate pregnancy at the beginning of the 21st century. This raises the possibility that OSA may be complicating pregnancy in obese women. At this time, there is a paucity of data regarding OSA in pregnancy, as the literature regarding the outcome of pregnancies complicated by OSA is limited to case reports. These reports have identified OSA in association with preeclampsia, intrauterine growth restriction, and stillbirth. We performed this cohort study to further explore the associations between the presence of OSA and adverse pregnancy outcomes.
Materials and Methods
This was a retrospective cohort study of women with a confirmed diagnosis of OSA who received their prenatal care at our urban tertiary care center and delivered between January 2000–December 2008. Comparative cohorts of obese (prepregnancy BMI of ≥30 kg/m 2 ) and normal-weight (prepregnancy BMI 18–24 kg/m 2 ) women without OSA, matched for year of delivery, were randomly selected in a 2:1 fashion for each OSA case using our electronic perinatal database in a masked fashion with random number tables. Multiple gestations and subjects with OSA without documentation of polysomnogram-confirmed OSA were excluded.
Medical records were individually reviewed for relevant demographic characteristics, clinical information, and pregnancy outcomes by a single reviewer (J.M.L.).
OSA diagnosis
All women included in the OSA group underwent standard 15-channel polysomnography (PSG). Sandman software (Covidien, Denver, CO) was utilized to collect data. Sleep was staged according to the scoring system of Rechtschaffen and Kales. Respiratory events were scored as follows: apnea, cessation of airflow for 10 seconds or longer with continued effort (obstructive) or lack of effort (central) to breathe; hypopnea, reduction of 10 seconds or longer (≥30%) in airflow accompanied by either an arousal or a 3% or greater reduction in SaO 2 .
The apnea-hypopnea index (AHI) was calculated by dividing the number of respiratory events by the duration of sleep in hours. The AHI was used to measure sleep apnea severity. OSA severity was graded according to American Academy of Sleep Medicine standards: AHI less than 5 is normal, 5–15 is mild, greater than 15–30 is moderate, and greater than 30 is severe. Continuous positive airway pressure (CPAP) was titrated to eliminate respiratory disturbances, attempting to achieve an AHI less than 5. Once this was accomplished, pressure adjustments could be made to eliminate snoring and reduce arousals. Women with an AHI less than 5 were considered normal and were not included in our analysis.
Outcome measures
A composite outcome of maternal morbidity was defined as 1 or more of the following: blood transfusion, conversion from regional anesthesia to general anesthesia, an unexpected surgical procedure (excluding cesarean delivery), postpartum endometritis, maternal sepsis or pneumonia, wound complications, prolonged postdelivery hospital stay (≥3 days for vaginal delivery and ≥5 days for cesarean delivery), intensive care unit admission, or hospital readmission.
Endometritis was defined as an elevated postpartum body temperature of 38°C or greater with uterine tenderness in the absence of findings suggesting a nonuterine source. A wound infection was defined as erythema of the incision accompanied by purulent drainage requiring wound care. Wound complication included any of the following: wound infection, wound seroma, or wound hematoma.
Preeclampsia was defined as new-onset hypertension (≥140 mm Hg systolic or ≥90 mm Hg diastolic) and proteinuria (≥300 mg on 24 hour urine). In women with chronic hypertension, the diagnosis was made based on an increase in blood pressure requiring multiple antihypertensive agents accompanied by worsening proteinuria.
Neonatal morbidity was defined as admission to the neonatal intensive care unit (NICU). Preterm birth was defined as delivery before a gestation of 37 weeks 0 days based on best obstetrical estimate.
Statistical analysis
Statistical analysis was performed using SPSS statistical software (version 16.0; SPSS, Inc, Chicago, IL). The normal-weight controls were used as the comparative group. Univariate analyses were used to compare demographic and clinical characteristics. The χ 2 test was utilized for binomial variables. Wilcoxon rank-sum test and the Kruskal-Wallis test were utilized for discrete and continuous variables. Multivariable logistic-regression analysis was performed to adjust for potential confounding factors for the maternal morbidity composite outcome and for preterm delivery. Nominal 2-sided P values are reported. P < .05 was considered statistically significant.
Factors included in the model for maternal composite morbidity were the following: maternal age at delivery (years), race (black vs nonblack), ethnic background (Hispanic vs non-Hispanic), tobacco use during pregnancy (yes vs no), type of insurance at delivery (government vs commercial), obesity (yes vs no), hypertension (yes vs no), diabetes (yes vs no), OSA (yes vs no), and cesarean delivery (yes vs no).
Factors included in the model for preterm delivery independent factors were the following: maternal age at delivery (years), race (black vs nonblack), ethnic background (Hispanic vs non-Hispanic), tobacco use during pregnancy (yes vs no), type of insurance at delivery (government vs commercial), obesity (yes vs no), hypertension (yes vs no), diabetes (yes vs no), OSA (yes vs no), and prior preterm birth (yes vs no).
This retrospective chart review was approved by the institutional review board at MetroHealth Medical Center.
Results
There were 68 pregnancies among 57 women with OSA. The first pregnancy with outcome information was selected for those with more than 1 pregnancy. The diagnosis of OSA was made before pregnancy in 33 women (58%). The remainder was diagnosed during pregnancy. All women diagnosed with OSA were recommended to use CPAP therapy, although compliance data were not available.
The median AHI was 22 (interquartile range, 12–44) events per hour. The median lowest O 2 saturation during an event was 87% (84–90%). OSA was moderate or severe in 36 of 57 women (63%). The control groups consisted of 114 obese and normal-weight women.
Demographic and clinical characteristics of the 3 cohorts are presented in Table 1 . Compared with normal-weight women, those with OSA had a higher BMI, were older, and were more likely to have a comorbid condition, including chronic hypertension, asthma, diabetes mellitus, and depression. We found no differences in the number of prenatal care visits between groups.
| Demographic | OSA (n = 57) | Obese (n = 114) | Normal weight (n = 114) | P value, OSA vs obese | P value, OSA vs normal weight | P value, obese vs normal weight |
|---|---|---|---|---|---|---|
| Insurance | .18 | .2 | .05 | |||
| Government | 43 (75.4) | 99 (86.8) | 87 (76.3) | |||
| Commercial | 12 (21.1) | 13 (11.4) | 18 (15.8) | |||
| None | 2 (3.5) | 2 (1.8) | 9 (7.9) | |||
| Race | .06 | .28 | .21 | |||
| Black | 36 (63.2) | 74 (64.9) | 64 (56.1) | |||
| White | 19 (33.3) | 24 (21.1) | 37 (32.5) | |||
| Hispanic | 2 (3.5) | 15 (13.2) | 11 (9.6) | |||
| All others | 0 | 1 (0.09) | 2 (1.2) | |||
| BMI, kg/m 2 | 46 ± 13 | 44 ± 7 | 22 ± 2.2 | < .001 | < .001 | < .001 |
| Age | 30 ± 6 | 27 ± 5 | 23 ± 5 | .36 | < .001 | < .001 |
| Smoking | 30 (52.6) | 51 (44.7) | 54 (47.4) | .34 | .5 | .79 |
| Nulliparous | 15 (26.3) | 36 (31.6) | 43 (37.7) | .27 | .08 | .4 |
| Prior PTD | 13 (22.8) | 11 (10) | 10 (8.8) | .02 | .01 | .84 |
| Chronic hypertension | 25 (43.9) | 12 (10.5) | 3 (2.6) | < .001 | < .001 | .03 |
| Diabetes | 17 (29.8) | 10 (8.8) | 1 (0.9) | .001 | .001 | .01 |
| Depression | 17 (29.8) | 8 (7.0) | 6 (5.3) | < .001 | < .001 | .8 |
| Asthma | 19 (33.3) | 10 (8.8) | 9 (7.9) | < .001 | < .001 | 1.00 |
| Number of prenatal visits | 8 ± 3 | 9 ± 4 | 9 ± 3 | .75 | .7 | .96 |
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