Obstetrics and Gynecology International

Review Article

The Problem of Confounding in Studies of the Effect of Maternal Drug Use on Pregnancy Outcome

Table 1

Risk of neonatal morbidity^a according to preterm birth and maternal use of CNS-active drugs^b after the first trimester (both 2nd and 3rd trimester). Among all infants, 6.0% were born preterm, and among infants of women using CNS-active drugs, 8.2% were born preterm.


Infant group	With neonatal pathology	Total number	%	OR	95% CI

All infants	22015	315975	7.0	1.00	Reference
Preterm births	7465	18836	39.6	12.3	12.0–12.7
CNS-active drugs, all infants	541	4425	12.2	1.83	1.67–2.00
CNS-active drugs, term infants	380	4009	9.5	2.05	1.84–2.28

Infant morbidity consists of one or more of the following conditions: respiratory disorders (ICD-10 codes P22–P28), hypoglycaemia (P70.4–P70.9), neonatal convulsions (P90), other disturbances of cerebral status (P91), low Apgar score (Apgar 5 minutes <7).
The drugs studies include opioids, anticonvulsants, antipsychotics, sedative/hypnotics, and antidepressants.