. 2014 Nov 10;4:6982. doi: 10.1038/srep06982

Table 1. Characteristics of studies included in the meta-analysis.

First author Year	Study size	age	Study type	Measure for OSA diagnosis	Maternal outcome	Neonatal outcome	Method for selecting participant	Inclusion	Exclusion	Confounding Variable
KoHS¹⁶ 2013	276	20–45	Prospective cohort study	Berlin questionnaire	Preeclampsia, gestational diabetes, Preterm birth	Cesarean delivery, NICU admission, SGA < 10th percentile	Random survey by means of a self-administered close-ended questionnaire	1. The questionnaire were properly filled in;	The questionnaire were not completed or the data of obstetric outcome were not fully available	age, obesity
								2. The data about obstetric outcomes were fully available.		BMI classification and the logistic regression was use to adjust the confounders
Louis J¹⁷ 2012	161	20–44	Prospective cohort study	Good quality: Portable PSG (AHI > 5)	Preeclampsia, gestational diabetes Preterm birth	Cesarean delivery, NICU admission	Randomly selected	1. Participants were obese, age 18 years or older;	1. Subjects with chronic use of narcotic or other drugs affecting the central nevous system and inability to maintain sleep beyond 2 hours;	Age, race BMI
								2. Participants received obstetric care by their physicians or nurse practitioners.	2.Women with a documented history of nonadherence.	Multivariable logistic regression model was performed after adjusting for the effect of confounders
Olivarea¹⁸ SA2011	220	18–50	Prospective cohort study	Berlin and Epworth scale	Preeclampsia, gestational diabetes	SGA < 10th percentile	NA	Gravidae of 18–50, with confirmed viable singleton gestations	Subjects with known sleep-disordered breathing and patients with significant underlying pulmonary or cardiac comorbidities, or with known multiple gestations	Age, obesity
										BMI classification and the logistic regression was use to adjust the confounders
Louis JM¹⁹ 2010	285	20–40	retrospective cohort study	Good quality: full PSG (AHI > 5)	Preeclampsia, Preterm birth	Cesarean delivery, NICU admission, SGA < 10th percentile	Random number table in a masked fashion	1.confirmed diagnosis of OSA	Multiple gestations and subjects with OSA without documentation of PSG confirmed OSA	Age, race, obesity
								2.Receive the prenatal care		Use the normal weight and obese as control group and the multivariable logistic regression analysis was performed
Sahin FK²⁰ 2008	35	22–42	Prospective observation study	Good quality: full PSG (AHI > 5)	Preeclampsia, gestational diabetes	NICU admission	NA	Pregnant women who agreed to participate in the study were scheduled for PSG and NST recording for one night after 34weeks of gestation.	Subjects who suffered from cardiac decompensation, or respiratory insufficiency or malignancy	Obesity
										Use the non-obese women with OSA as control

OSA: obstructive sleep apnea; BMI: body mass index; PSG: polysomnogram; SGA: small for gestational age; NICU: neonatal intensive care unit.