Drawing depicting the skeleton of a child from Dutch anatomical text (1690).
In 1624, Parliament passed an act that made murdering or concealing the death of an illegitimate child illegal. It stated:
Whereas many lewd women that have been delivered of bastard children, to avoid their shame, and to escape punishment, do secretly bury or conceal the death of their children, and often, if the child is found dead, the said women do allege, that the said child was born dead…. Be it enacted … in every such case the mother so offending, shall suffer death as in the case of murther, except such mother can make proof by one witness at the last that the child . . . was born dead. 
Implicit in this statement is the assumption that poor, unmarried mothers were promiscuous, immoral women who, ‘having committed one sin’, were capable of committing an even greater sin—that of infanticide. During the 17th century, numerous publications appeared characterising the unwed mother as a ‘lewd whore’. The 1634 ballad, No Natural Mother but a Monster, traces a young girl’s fall from grace—beginning with premarital sex, followed by the pregnancy and eventual strangulation of her bastard child, and ending with her own execution on the scaffold.  [Read about Anne Greene, executed for infanticide, here].
During the 18th century, however, attitudes began changing as focus shifted from the sinful natures of unwed mothers to the medical evidence presented in court. Surgeons, in particular, were increasingly called upon to perform post-mortems on dead babies and then testify as to the cause of death in cases of suspected infanticide. 
In 1783, the surgeon and male-midwife, William Hunter, presented a lecture On the Uncertainty of the Signs of Murder in the Case of Bastard Children to members of the Medical Society. In it, he cautioned that those testifying to the cause of death in newborns should ‘have seen many new-born children, both stillborn, and such as had outlived their birth a short time only’. Moreover, a surgeon acting as a medical expert in cases of infanticide should have ‘dissected, or attended the dissection of a number of bodies in different stages of advancing putrefaction’, for Hunter himself had ‘often seen various common and natural appearances, both internal and external, mistaken for marks of a violent death’. 
The new emphasis on medical evidence led to an increasing number of acquittals in the 18th century. On 17 July 1717, Ann Hasle was found not guilty of drowning her newborn baby after a surgeon examined the child’s corpse and found no water in its lungs.
The surgeon being call’d to give his Opinion on the Matter, confirm’d his Lordship’s Opinion, deposing upon Oath…that no human Body could be drowned without receiving some Quantity of Water into the Body, and consequently the Child could not be alive when put into the Copper. 
Even in cases where the baby had been born alive, a surgeon could present evidence which might lead to an acquittal. On 5 December 1733, Joseph Sandford—a surgeon in Goodman’s-Fields—told the court that he found the blood vessels of Mary Doe’s infant ‘empty, and the Navel-string lacerated, and not ty’d’, thus concluding that child had accidentally bled to death.  A similar opinion was expressed by the surgeon testifying in the case of Mary Robinson on 24 February 1768. 
Although the law had not changed, it became increasingly difficult to convict an unwed mother of infanticide without the same level of evidence required to convict someone of murder. This, along with changing attitudes towards unmarried mothers themselves, undoubtedly saved many necks from the hangman’s noose in the 18th century. [For more about hangings click here].
1. 21 Jac. I, c.27, ‘Act to Prevent the Destroying and Murdering of Bastard Children’.
2. No Natural Mother but a Monster (London, 1634), repr. in Pepysian Garland, pp. 425-30.
3. For more on this subject, see Mary Clayton, ‘Changes in Old Bailey Trials for the Murder of Newborn Babies, 1674-1803′, in Continuity and Change 24 (2009): pp. 337-359.
4. William Hunter, On the uncertainty of the signs of murder in the case of bastard children (London, 1818), p. 20.
5. The Old Bailey Proceedings Online (www.oldbaileyonline.org) (henceforth OBP), July 1717, Ann Hasle (t17170717-18).
6. OBP, December 1733, Mary Doe (t17331205-20).
7. OBP, February 1768, Mary Robinson (t17680224-42).