Association Between Low Plasma Glucose After Oral Glucose Tolerance Test in Pregnancy With Impaired Fetal Growth

Objective: To study the association of low maternal plasma glucose in 2 hour 75 g oral glucose tolerance test (OGTT) in women with impaired birth weight and determinate if this result is predictive of low birth weight (\<10th percentile according to the INTERGROWTH-21st newborn weight standards for gestational age/sex).

Materials and methods: OGTT at 24-34 week gestation will be performed in pregnant women, the birth weight will be compared between women with low fasting plasma glucose (FPG) (\<10th percentile, \<65 mg/dL) and normal FPG (≥10th percentile, ≥ 65 mg/dL) also for 1 and 2-hour plasma glucose (1-h PG/2-h PG). Receiver operating characteristic curve analysis will be used to determine the optimal lower OGTT threshold for the prediction of low birth weight.

Maternal hypoglycemia has been reported to be linked with low birth weight and poor neonatal outcome. OGTT is performed routinely in pregnancy and hypoglycemia following this screening test is often encountered and the implication of this finding for the fetal growth is unclear.

The aim of study will be determinate the association of low maternal plasma glucose in OGTT in women with impaired birth weight and determinate if this result is predictive of low birth weight (\<10th percentile according to the INTERGROWTH-21st newborn weight standards for gestational age/sex).

The study population will consist of patients with singleton pregnancies who will undergo OGTT at 24-34 weeks, have regular medical checkups throughout their entire pregnancy, deliver on or after 25 week gestation and fulfill inclusion criteria.

The birth weight will be compared between women with low fasting plasma glucose (FPG) (\<10th percentile, \<65 mg/dL\*) and normal FPG (≥10th percentile, ≥ 65 mg/dL) also for 1 and 2-hour plasma glucose (1-h PG/2-h PG). Receiver operating characteristic curve analysis will be used to determine the optimal lower OGTT threshold for the prediction of low birth weight.

This study will be performed according to the standards of the Helsinki Declaration and approval was obtained from the ethics and educational issues coordinating committee of our University Hospital.

\*Determinated previously in a pilot study

Eligibility Criteria:
Inclusion Criteria:

* Women with singleton pregnancy who underwent OGTT at 24-34 weeks and had regular medical checkups throughout their entire pregnancy.
* Gestational age was determined based on the last menstrual period. If gestational age according to the last menstrual period differed by more than 7 days from that according to ultrasonography at \<11 weeks, the latter was used to assign gestational age.

Exclusion Criteria:

* Inaccurate gestational age
* OGTT being drawn outside the prescribed window of 24 to 34 weeks gestation.
* Patients who could not swallow the OGTT solution or vomited afterward were excluded from the study.
* Patients who were diagnosed with gestational diabetes at any time during their pregnancy were excluded.
* The following comorbidities or complications that could affect fetal growth also were excluded: cardiac disease, preeclampsia, gestational hypertension, tobacco use, alcohol intake, stimulant drugs use, maternal systemic diseases (e.g., hypertension, pregestational diabetes, autoimmune disease, thrombotic disease, thyroid disease), intrauterine infectious diseases (e.g., cytomegalovirus, rubella, toxoplasmosis, syphilis), major neonatal anomalies or genetic and structural disorders (e.g., trisomy 21, trisomy 18, trisomy 13, congenital heart disease), placental disorders, and umbilical cord abnormalities.
* Patients with high risk for preeclampsia, intrauterine growth restriction, trisomy 21, trisomy 18 and trisomy 13 in the first trimester screening test.
* Patients with incomplete or missing data were also excluded.