[Tujuan: Penelitian ini bertujuan menilai hubungan laktat ibu dan laktat arteri umbilikalisdengan asidemia janinMetode: Penelitian desain uji diagnostik dengan 42 ibu hamil dengan janin tunggal hidupusia gestasi ≥ 34minggu dengan FDJP < 5 atau kecurigaan asidemia janin di Rumah Sakit Dr.Cipto Mangunkusumo pada bulan November 2012 hingga Februari 2013. Laktat ibudievaluasi segera saat ditegakkan diagnosis kecurigaan asidemia janin, analisa gas darah danlaktat arteri umbilikalis diambil segera saat bayi lahir. Asidemia janin ditegakkan dengan pHarteri umbilkalis < 7,2. Kadar laktat diukur dengan menggunakan Lactate Pro. Nilaidiagnostik laktat ibu dan laktat a.umbilikalis untuk memprediksi asidemia janin diuji denganmetode Receiver Operating Character (ROC).Hasil: Sebanyak 39 subyek penelitian yang diperoleh data laktat ibu & laktat arteriumbilikalisnya dan 3 subyek penelitian yang diperoleh data laktat ibunya saja. Untukmemprediksi asidemia janin laktat ibu mempunyai akurasi 88.9% (IK 95% 0,791-0,987).Secara statistik terdapat asosiasi antara laktat ibu dengan asidemia janin (p<0,001). Bila kadarlaktat ibu ≥ 4,70 mmol/l akan dapat diprediksi akan terjadi asidemia janin sebesar 92%.Sedangkan bila kadar laktat ibu < 4,7 mmol/l maka prediksi tidak akan terjadi asidemia janinsebesar 58,8%. Untuk memprediksi asidemia janin laktat arteri umbilikalis mempunyaiakurasi 82,4% (IK 95% 0,660-0,988). Secara statistik terdapat asosiasi antara laktat arteriumbilikalis dengan asidemia janin (p=0,035). Bila kadar laktat arteri umbilikalis ≥ 4,1mmol/lmaka akan diprediksi akan terjadi asidemia janin sebesar 88,89%. Sedangkan bila kadarlaktat arteri umbilikalis < 4,1mmol/l maka prediksi tidak akan terjadi asidemia janin sebesar75%. Secara statistik terdapat hubungan antara laktat ibu dengan laktat arteri umbilikalis(p=0,017). Semakin bertambah laktat ibu maka semakin besar laktat arteri umbilikalisnya(r=0,238). Tidak ada hubungan secara statistik antara nilai Apgar dengan laktat ibu (AUC60,6%), laktat arteri umbilikalis (AUC 65%) dan asidemia janin (AUC 65%). Tidak adaperbedaan nilai AUC antara laktat ibu dan laktat arteri umbilikalis dalam memprediksiasidemia janin (p=0,515)Kesimpulan: Laktat ibu dan laktat arteri umbilikalis memenuhi standar uji diagnostik yangbaik untuk memprediksi kejadian asidemia janin. Laktat ibu dapat memprediksi asidemiajanin sebelum bayi lahir, Objectives: To asses the association among maternal lactate and umbilical arterial lactate with fetal acidemiaMethods: This was a diagnostic test study, which was held on the 42 pregnant women with a singleton live fetus, gestational age ≥ 34 weeks and modified biophysical profile < 5 or suspected fetal acidemia at Dr. Cipto Mangunkusumo Hospital from November 2012 until February 2013. Maternal lactate was evaluated immediately at the time that the diagnosed of suspected fetal acidemia was established. Blood gas analysis and umbilical arterial lactate were taken immediately when the baby was born. Fetal acidemia is defined as umbilical arterial pH <7.2. Lactate levels were measured using the Lactate Pro. Diagnostic value of maternal lactate and umbilical arterial lactate to predict fetal acidemia was tested by the method of Receiver Operating Character (ROC).Results: Both maternal and umbilical arterial lactate were obtained from 39 subjects. Maternal lactate only was obtained from 3 subjects. To predict a fetal acidemia, the maternal lactate has an accuracy of 88,9% (CI 95% 0,791- 0,987). There was an association between fetal acidemia and maternal lactate statistically ( p<0.001). If maternal lactate levels ≥ 4.70 mmol / l, it would be predicted that 92% fetal acidemia are occurred. Meanwhile, if maternal lactate levels <4.7 mmol/l then there will be a prediction that 58.8% was no fetal acidemia. To predict a fetal acidemia, the umbilical arterial lactate has an accuracy 82,4% (CI 95% 0,660-0,988). There was an association between fetal acidemia and umbilical arterial lactate statistically (p=0,035). If umbilical arterial lactate levels ≥ 4,1 mmol/l, it would be predicted 88,89% fetal acidemia are occurred, meanwhile if umbilical arterial lactate levels < 4,1 mmol/l then there will be a prediction that 75% was no fetal acidemia. Statistically there was an association between maternal lactate and umbilical arterial lactate (p=0,017). If maternal lactate increased, the umbilical arterial lactate would be increased (r=0.238). Statistically there was no association between Apgar score with maternal lactate (AUC 60.6%), umbilical arterial lactate (AUC 65%) and fetal acidemia (AUC 65%). There is no difference in AUC values between maternal lactate and umbilical arterial lactate in predicting fetal acidemia (p = 0.515)Conclusion: Maternal lactate and umbilical arterial lactate meet a good standard diagnostic test for predicting the incidence of fetal acidemia. Maternal lactate can predict fetal acidemia before the baby is born.]