What's your idea of the perfect birth? Do you want every medical intervention known to science or do you want to go it alone, without the help of a doctor or midwife? And what about after birth? Perhaps you'll hang on to your baby's placenta and carry it around with your newborn until it dries and drops off naturally? Or maybe you'll decide to eat it by whizzing it up into a smoothie? This film follows four pregnant women all making very different choices around their births, all determined to do it their way." 37-year-old Jo plans to deliver her baby completely alone on board her barge, without the assistance of any medical professional. By contrast, 34-year-old Anna is opting to sidestep the pains of labour and book in for a c-section at the Portland Hospital in London. Anna wants all the medication available and she doesn't want to feel a thing. There are plenty of unusual plans for after the birth too. In Devon, 33-year-old Lisa plans to lotus birth - she'll leave her baby's umbilical cord attached to its placenta and she'll keep it fresh by dusting it with salt, rose petals and lavender oil. 35-year-old Kati from Manchester is going to whizz her afterbirth into a smoothie and consume it over a number of days. She hopes it will help her stave off post-natal baby blues and bounce back as quickly as possible. Fending off bewildered looks and concerns from friends, family and medical professionals, each woman is going against convention to have the birth she wants. There are free and frank discussions between mums and daughters and decisions to go against medical advice. So does breaking with the norm and sticking to your guns pay off? And what really is the perfect birth?

This episode explores the nature of the greenhouse effect (discovered by Joseph Fourier and Svante Arrhenius), and the evidence demonstrating the existence of global warming from humanity's influence. Tyson begins by describing the long-term history of the planet Venus; based on readings from the Venera series of probes to the planet, the planet had once had an ocean and an atmosphere, but due to the release of carbon dioxide from volcanic eruptions, the runaway greenhouse effect on Venus caused the surface temperatures to increase and boiled away the oceans. Tyson then notes the delicate nature of the amount of carbon dioxide in the atmosphere can influence Earth's climate due to the greenhouse effect, and that levels of carbon dioxide have been increasing since the start of the 20th century. Evidence has shown this to be from mankind's consumption of oil, coal, and gas instead of from volcanic eruptions due to the isotopic signature of the carbon dioxide. The increase in carbon dioxide has led to an increase in temperatures, in turn leading to positive feedback loops of the melting polar ice caps and dethawing of the permafrost to increase carbon dioxide levels. Tyson then notes that humans have discovered means of harvesting solar power, such as Augustin Mouchot's solar-driven motor in the 19th century, and Frank Shuman's solar-based steam generator in the 1910's. Tyson points out that in both cases, the economics and ease of using cheap coal and oil caused these inventions to be overlooked at the time. Today, solar and wind-power systems would be able to collect enough solar energy from the sun easily. Tyson then compares the motivation for switching to these cleaner forms of energy to the efforts of the Space race and emphasizes that it is not too late for humanity to correct its course.