L-carnitine has an important role in the control of oxidative stress and lipid β-oxidation during in vitro culture and cryopreservation of ovarian follicles, oocytes and embryos. This substance balances the acetyl-CoA/CoA ratio, maintains glucose metabolism and increases energy production in mitochondria. It also plays a key role in reducing endoplasmic reticulum stress, by transferring palmitate to mitochondria or eliminating it to avoid toxicity. By eliminating reactive oxygen species, L-carnitine increases the percentages of mature oocytes with uniform mitochondrial distribution and improves embryo post-thaw cryotolerance. Therefore, L-carnitine controls lipid β-oxidation and oxidative stress during in vitro culture of ovarian follicles, oocyte maturation, embryonic development and cryopreservation.

A single umbilical artery (SUA) was identified in 1.5% of twin pregnancies. The presence of a SUA in a twin pregnancy was associated with a 50% incidence of fetal anomalies, many of them complex and severe. The embryology and pathophysiological mechanisms associated with a SUA are reviewed. Aneuploidy is relatively common and should be considered, particularly in the presence of associated anomalies. Fetal growth restriction is frequent and preterm delivery is common.

To determine the prognosis of an isolated single umbilical artery (SUA) in a twin pregnancy, we selected twin pregnancies with a second trimester ultrasound diagnosing a SUA in at least one fetus at our tertiary hospital. This was confirmed by placental histopathology or by expert review of ultrasound images. Cases were identified by searching the hospital ultrasound database over a period of 7.5 years. Higher order multiples or coexistent aneuploidy or major anomalies were excluded. Each case of an isolated SUA was assigned three consecutive twin pregnancy controls paired for chorionicity and maternal age. Primary outcomes were preterm birth <34 weeks, small for gestational age (SGA) or perinatal death. Other outcomes included antenatal growth restriction, mode of delivery, and admission to neonatal intensive care or special care nursery. Nine pregnancies (18 fetuses) were identified for analysis as cases. Isolated SUA was associated with preterm birth <34 weeks (odds ratio = 12.2; 95% CI = 2.0–75.2; p = .005) but not for SGA. There was also no difference in SGA between the affected twin and its normal co-twin. Perinatal death was increased but after controlling for gestational age and clustering this finding was no longer significant. We conclude that isolated SUA in twins adds a degree of risk to an already high-risk pregnancy but does not increase the need for surveillance for growth restriction.