The primary outcomes and secondary outcomes?

In the context below, does "primary outcomes" refer to "primary adverse pregnancy outcomes"?

Why is there "secondary outcomes" since it is just an experiment to "undergo 75-g oral glucose-tolerance testing at 24 to 32 weeks of gestation"? I think that it may be only one "outcomes" . It is "adverse pregnancy outcomes"!

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Context:


Hyperglycemia and Adverse Pregnancy Outcomes

The HAPO Study Cooperative Research Group

ABSTRACT

Background It is controversial whether maternal hyperglycemia less severe than that in diabetes mellitus is associated with increased risks of adverse pregnancy outcomes.

Methods A total of 25,505 pregnant women at 15 centers in nine countries underwent 75-g oral glucose-tolerance testing at 24 to 32 weeks of gestation.

Data remained blinded if the fasting plasma glucose level was 105 mg per deciliter (5.8 mmol per liter) or less and the 2-hour plasma glucose level was 200 mg per deciliter (11.1 mmol per liter) or less.

Primary outcomes were birth weight above the 90th percentile for gestational age, primary cesarean delivery, clinically diagnosed neonatal hypoglycemia, and cord-blood serum C-peptide level above the 90th percentile. Secondary outcomes were delivery before 37 weeks of gestation, shoulder dystocia or birth injury, need for intensive neonatal care, hyperbilirubinemia, and preeclampsia.

Full context:
http://content.nejm.org/cgi/content/short/358/19/1991